As a Stihl dealer and small engine mechanic, I can tell you I have seen this all to often. Most of the time’s it happens because d valve clearance isn’t checked/adjusted often enough. I Alwas recommend to check the valve clearance at least annually. Ore the ,,hammering” of the those shoes that ride in the Cam, will destroy it…… The reason why they made it out of Plastic in the first place, is because of lubrication. Greatings to you and anyone how reads this: Jan from Switzerland PS: There may be some grammar error’s in this text, English isn’t my strongest language 😅
@Jan, I am not convinced of this explanation - why would hammering make it wear all the knob down in one catastrophic event as explained by Jon? It makes no logical sense. I would suspect either lack of lubrication or over-heating. One could amplify the other. "Plastic" obviously does not support overheating together with mechanical stress. Could misadjusted valves mean higher operating temperature? Was the machine running extra hot when you used it Jon?
Sorry Still dealer but there is absolutely no reason other than cheap out (or turning more pieces per the same time spend to make one in Brass, since with injection moulding you can pump let's say 10 per cycle while you make one on a CNC) for that cam being made of plastic other than a metal. Don't want to make it so good that it doesn't go bad anytime right, or the after sales would lose profit and new sales also drop since why I would buy a new one if my old 20 year something still runs like a champ?
Why would a company that has been the Mercedes of small industrial engine quality elect to build an engine with plastic cams? I have a 22 year old Ryobi 4 stroke 845r 25 cc 4 stroke engine that finally wore out after 22 years of pretty steady use and it wasn't the cam it was the flywheel, you cannot find replacements for these once the keyway wears out. Nowadays Ryobis have plastic cams and their cams are OHC where all the engine heat is, in the head. Why Stihl didn't take Honda's little GX 4 stroke engine tech to heart is a head scratcher. I also have a Honda GX31 pump engine I bought used in 1998 and it still runs like the day it was made.
I agree with ya bud i do think his oil has been pretty sub par aswell Small engines mech 30 years here. Normal ill see pitting and the comp release failed never seen a melted one that bad. In the fleet i work on we have 40 + of these units.
Love how you always diagnose unusual problems and explain why you are doing a particular "trial" in attempting to isolate the root cause of the failure.
In today's "throw away" mentality, I think replacing a $15 part on a 10 year old tool would definately be considered a WIN. Glad you were able to find the part and replace it easily. Thanks for posting!
@@jomarcruz659 being a small engine mechanic, what do you think of how comically cheap the off shore carbs have gotten? I bought a couple that were less than $12, have had great luck with them (not to say they're all ok). I've even bought a carb that came with a tune up kit air/fuel filter, spark plug, fuel lines, etc for less than $20. Even if they straight up copied the design, they still had to buy the stock, program and run probably 30+ cnc operations, assemble it, package it, warehouse it, advertise it, and ship it halfway around the world for less than what a subway sandwich now costs. It's just insane to me. I know labor costs are next to nothing over there, but holy crap.
About 20 years ago, I installed a new telephone system at Tecumseh's warehouse in Slough, UK... I was shown around, and was impressed by all the stock they held... Chatting with the boss of the operation, I was told that their mower engines were designed to last 100 hours at most... or two average years of garden mowing... shocking!
Lets not pretend like nobody saw the little bulldozer and and track loader in the outro. Are those future projects by any chance? Love your videos, you are doing a fantastic job.
This has to be one of my favorite small engine repair vlogs of yours. The instruction and explanations are invaluable to a novice small engine repair guy. Thank you. I learned a great deal.
The issue with the clutch is that the pins the shoes pivot on are rusted into the shoes, you need to punch out the pins and remove the rust to allow the shoes to pivot nicely.
You know that you love some FarmCraft101 when you see the notification pops up on your phone that a new video was posted. You park your tractor and head to the house to watch the new video. Not disappointed eighter, it's another great video.
This video was incredibly well done. I appreciated getting to see your entire diagnostic process and your skill in taking apart and reassembling all the parts. What I liked best is your ability to teach how each part functions as you went thru the process. Most of us would never have access to this level of expertise at our local small engine repair shops. Thanks so much.
Always wondered how a compression release worked. Now I know, thanks. Saw the cows around a brush fire, but no close up on Big Mama. How is her hip? Got in one Seal camo, check.
Enjoyable, venture into a Sthil multitool. All these producks have a built in manufacturers end life. You have the confidence and skill to dismantle and rebuild, most owners do not . Result is machines get trashed and new ones are purchased. C’est la vie. Thank you.
I really like my Stihl equipment - have always been a Stihl guy, owned half a dozen saws and several trimmers including a 2 stroke kombi system setup. My only real complaint was the carb on my MS-180 saw, replaced it with one that could actually be tuned and it runs way better. The rest have been great. Their low end homeowner products are way better than any of the other low cost competitors!
Love your small engine videos. I've got a Craftsman 2cycle weedeater that is 30 years old and after replacing the fuel lines and tank filter and periodically adjusting the carb and greasing the cable drive, it still runs great.
Jon, Thanks for the teardown, repair, and all the explanations! Always good and the viewer might even learn something they didnt know, as I did about the 4 stroke but mixed oil/gas. That cam was terrible, glad you got it fixed!
Have the exact same unit and around the same age. Thanks so much for documenting the maintenance and repair. I think I'll need to adjust my clutch like you did.
Ditto. I have the same one. So far mine “just works”. I’ll be on the lookout. Watching further into the video… ick. I’m not happy. I have 4 of the attachments in think. It’s really nice to only have 1 engine to maintain.
I am a former Stihl dealer. In the 70’s and 80’s I don’t think that you could get a better quality unit. Sadly everything I have purchased in the last 10 years is plagued with problems that shouldn’t happen. Foreign material in the carburetors. Bad coils. Bad plug wires. Bad tank vents. On and on and on….. no more Stihl for me.
Great to see your process but you should check the hole in the cover plate where the cam gear shaft rides. It opens out letting the shaft wobble causing it to wear early. That's what happened to my 131 so I had to replace the plate as well.
That's pretty interesting. I have a KM-56-R powerhead and those same attachments, plus an edger. It's a nice little system. The KM-56-R is a true 2-cycle, but I had to go pull the engine diagrams to confirm that. I never looked too closely at it because it's always just run :)
My dad has a troybilt tiller that has a two stroke, but runs on regular gas. It has a oil tank that you fill everytime that you fill with gas. It mixes the oil into the gas at the carburetor. It's weird.
Nice fix, the early honda gx25 engines had a similar problem when run to hot the plastic cam melted, they changed from gear driven to notched belt driven cam. Also Stihl uses they're own brand of Dirko sealant which is also orange (easily mistaken for rtv) but looking at the crankcase when you took it apart i'd say someone has been in there before, i've never seen Stihl use overkill amounts like that. When it comes to you're clutch there are crush tubes in the pivoting ends of the shoes that are frozen in place (hence clutch will only work with bolts loose) you need to free up those crush tubes in the shoes. if you leave it the way it is it will ware through the bolts and cause more damage!! Good luck with it, thanks for posting!
Nice video. Practical, helpful and with your usual sense of humor. While not rebuilding the boom lift hydraulics, this video was equally as interesting and probably more useful for us folks. From my experience replacing that carb diaphragm that's a little stiff will help with engine performance and response. The clutch hanging up could have also contributed to the cam wear so fixing that should help. I have also noticed a difference when using Stihl's fuel or Aspen fuel vs. pump gas or other canned fuel, for what it is worth. Looking forward to next week's video.
It doesn't make sense for commercial guys, but I only run Stihl gas. I don't worry about it sitting, things start and run fantastic on it. My 4 Stihl engines are going on 3-5 years old and all start with little to no fuss.
Great job John! You are a constant inspiration to a mechanical hacker who can "almost" fix anything, well at least dismantle things properly.. I had a 4 stroke Ryobi back in the day that suffered a similar failure from a plastic cam melting down to round. Of course I instantly ditch it and used the excuse to buy a new 2 stoke Toro that is still going many years later. Didn't discover the real problem until my curiosity got the best of me and I took the old Ryobi apart. I was shocked to see the cam lobe was plastic and still to this day wonder what engineer thought that was a good idea. More likely to have been the result of the final design being re-engineered by the accounting department! Well done.
Rough machining, heat treating and grinding a hardened steel cam would probably be one of the most expensive steps in making an engine like this. The plastic is adequate for most uses (so long as you don't overheat or over rev) and way cheaper to make because it can be produced by injection moulding.
Mr John your videos are some of the most informative on the internet. I work for a Stihl dealer and didn't know about the camshaft. We never get in to the engine that far. One of our stores work on all the units, I just do the small stuff. Thank you for the crash course in rebuilding the engine. Thanks for everything you do for the videos
I used to work with a light 2 stroke Stihl about 30 years ago. It was a brush cutter, not a combi tool. It was great! Also the duo handle bars on that machine work way better for the long term. But maybe not that handy when using the saw 😉 Great video.
Excellent video - thanks. My main takeaway is that a key diagnostic to look out for is the engine being hard to turn over due to the compression release not working - if you have this symptom you might think it is normal and not think anything of it - that is what I did for a while as I was unaware of the compression release feature. So if you experience this then I would say it is definitely worth checking the cam - and specifically the little valve release lug shown in the video at 34:30 - and while you are at it, the valve clearances. Fixing Stihl products is a hobby of mine. My gardener has the KM130R and had the metal plate on the back of the cam detach and disintegrate into two pieces with the little weight loose in the engine...also signs of melting. Surprisingly little damege - just the mounting point for the cam on the engine block where the pin goes in was quite badly worn and scored so I cleaned it up as best I could and then placed a 0.1mm shim between the cam and the engine block. Hard to work out why the failure has occured as plenty of lube evident. I have the same model so decided to replace mine prophelactically - was worn down by 0.2mm, and the metal back plate seemed loose. (I also had a broken valve a couple of years ago, so have done the full engine tear down in the video.)
If you think about it, the valves only opening a tiny amount, they were basically acting as an artificial throttle. It was coincidentally just enough air/fuel to idle, but that’s it. You opening the throttle on the carb changed nothing, since it simply couldn’t breathe more than it could at idle. What is odd to me is how quickly you report it happened. Maybe the cam somehow has a harder surface, and once it was compromised, the rest got lathed down really fast? Idk how that could be true with plastic, but I’m no polymer engineer, so I’ll leave it to others to figure that out.
It's a failsafe feature. It's supposed to give you some indication of improper running, and needs maintenance. Saving on damage to the rest of the valvetrain. It's a common wear item, especially the compression relief. However, some of their 4mix engines, suffer from damage due to no rod bushings. Certain models have them, while others don't, leading to serious damage, and needing a complete engine. Which costs as much as buying a new piece of equipment. Go figure 😢
This is why most people just buy a new tool. I would never get all the parts back in place and eventually end with it in the scrap pile. Thanks for the tutorial & the explanation of all the functions. The camera angle was great. I was right up in there the whole time. Thanks!
This came out at a perfect time, my primer bowl on my FS 130R STIHL trimmer got a hole in it the last time I used it. I’m glad I didn’t use it to long. I don’t wanna melt the cam-gear!! By letting it run lean!! Thanks so much for your videos!! Thought I knew a lil bit, but learning a lot from you!! God Bless, stay safe out there!
Funny, I've got roughly the same combi unit here for the house, maybe a model or 2 newer but about the same.. always wondered why it randomly misfires with a heavy load on it (usually the blower @ full throttle), now I know it's got a nylon cam that's likely worn out. Learn something new every day! Caught a little foreshadowing at the very end too 😉
I have the same thermal camera but from a different brand (vevor) and I love it. Its great for electrical work and unlike older ones the refreshrate is high enough to not bother you. Only downside is that when it changes thermal range it freezes for a bit and it does that quite often.
We use Stihl since at least 2001. We have multiple saws, Weadaeters/Brushcutters, hedgetrimmers and leafblowers. We never had any Stihl related problems, most of them were my dads and granddads user errors. So all in all we are quite happy with them. The biggest problem is that the plastic and rubber parts start to dissolve and dont work as intended
I have two FS90s (one in service, one not) that have the same engine. It's highly likely that I don't have nearly the same hours on either that you have on this unit, but this sure makes me want to take them apart and check on that plastic cam. Thank you for the in-depth coverage.
The second time I saw this. I am fascinated with the 4 cycle engine, but using two-stroke fuel!!! I used to teach small gas engine repair in a Middle School. I never saw students (who usually did poorly inside the school in their regular classes), but gave full attention to their own old engine piles outside. Never ceased to get the parts together and running.
Thank you for this video, it was a pleasure to watch as always. The STIHL "4-Mix"-engine has a good reputation for being durable, small, light and powerful. The idea to get rid of all that oil-cycle-fixtures like oil pan, - pump etc. by just using 2-stroke-mixture is kind of genius. You can use the same fuel for 2- and 4-stroke-engines on your STIHL tools without the danger of damaging the 2-strokes and without the hassle of stocking different fuel cans for various tools. And the engine is lighter without the oil cycle apparatus. I think that this engine looked incrdible well for 10 years of farm use. I personally never had issues with STIHL tools, but if you want to see flimsy engineering take a look inside the cheap chinese made garden motor tools for hobbyists.... I think that the plastic cam did exactly what it was supposed to: It's the weakest point in the mechanism but on purpose, because it fails in the case of under-lubrication first, throtteling the engine down and preventing further and much more costly damage. The gasket material in the engine was surely not intentional, but maybe it was hardening out or something so that this happened after so many years.
I still find it interesting that some say they notice a weight difference between mini 4 stroke and 4mix or 2 stroke engines. My echo PAS2620 and Honda HSS25 are similar displacements and feel very similar in overall weight and the Honda has an oil sump and the extra mechanics to use it at different angles. The Honda is relatively well balanced and quieter to boot compared to Stihl's 4mix. Same goes for the Echo, it's a touch quieter than the Stihl.
When I checked my valves on my km131r I also have bits of rtv up in the valve cover and I think I had some in that carbs pulse line to but I can’t remember.
Always a good time when you've uploaded a new video. With this one I did cringe a bit the way you were turning those needle screws like there was no tomorrow 🙂 My experience is they need small adjustments, and wait a bit after each. It takes some time for the carburettor to respond. But other than that I'm impressed with the way you explain things as you discover them. Great job !
The zama carbs on the 4 mix don't react to the needles much, they have a fixed jet inside, so even a half turn only has a small effect on actual fuel delivered. These aren't like the needle metered carbs on older chainsaws.
Very informative. Thank you sir. As a veteran landscaper I recommend taking the guard off for longer string, better access, less weight and much faster work. Ive used the Stihl 110' and 111's for a long time but a couple of years ago switched to echo 2620 model and wont be going back to Stihl. Much smoother trimmer.
As Taryl recently said: it will all soon be batteries only. However, this was a very well made and informative video. Reminded me of when I split my first chain saw wide open and replaced the crank bearings and piston rings ... about 40 yrs ago.
Hi John I have a fs90r strimmer as well. I had problems with my cam as WELL, The housing you removed to gain access to the cam on my machine had wallowed out where the pin the cam ran on a nd the cam was knackered as well, and sticking clutch, the clutch shoes should pivot on the shoulders where the bolts go thru, the pivots are bad for seizing, thats why when you tightened the clutch shoe bolts they lock up. Your clutch bolts realy nead to be tight. These trimmers work good when all is good. KEEP UP THE GOOD FIGHT, love the vids
MAKE SURE you use the Sthl oil in those 4mix engines. They require special oil or you’ll wear the cam and the bearings early. There’s other videos on this subject.
Lies. Oil and fuel is just that. Higher or lower octanes and more or less oil is really the only differences you can make. Stihl oil when burnt burns almost to like a yellow o believe so if you use a different kind of oil in it when they check your warranty they look to see the oil you've been using has been burning yellow in the exhaust/muffler. They don't add some special additives or nothing it's just marketing.
@Steve just Steve never use ethanol gas and use 91 when mixing and you'll never have any issues starting or running and it can sit all winter pick it up next summer it'll fire right up. Non ethanol gas doesn't break down like corn gas does. And your fuel lines won't get brittle.
@@shaynewalker4519 it’s actually is very true. The 4 mix engines require some wear additives in the oil to help lubricate the piston pin bearing which in that engine is a normal bushing, not a needle bearing. It also needs the additives to prevent wear on the cam shaft. You are correct about the non ethanol gas though. My cheap Ryobi string trimmer starts on the first pull with ethanol free gas.
I have a Stihl backpack blower along with about 12 other Stihl pieces of equipment. They all have great warranty. The blower just went in for minor repairs. 4 year bumper to bumper warranty. Outstanding
Great work! I always learn so much from you! And.. if one of those cows got much closer to the fire, y’all would have had some bbq for dinner! Thanks for all your content!
I picked up a broken FS-90 a few years ago which has the same exact power head assembly, someone had stepped on it and broken 2 of the tabs off of the bottom case which support the shaft so I had to do a full engine tear down to replace the broken stuff. My local dealer was really helpful, they sold me that $20 tube of OEM Stihl "Dirko HT" RTV to put everything back together and one of the repair techs warned me not to use to much like Stihl does sometimes because the pieces will eventually get into the engine and do exactly what you're repairing. Pieces get into the gap and wear down the plastic cam gear.
That worn cam lobe is probably the result of a bad batch of whatever material it's made of. Reminds me of an issue Harley Davidson had with cam chain tensioners about 20 years ago. A number of engines grenaded because of it. Great eye opening video. I've always been a Stihl fan but from your experience and what I have seen on other channels, I may be changing over to Husqvarna.
Well done. I just had a problem with the engine not starting easily and adjusted the valves. The FS 110 R runs really well now and starts with one pull after a simple valve adjustment. Like Jan said, I think maintaining proper valve adjustment is critical to not overheating and other operating problems. All good information. I will keep an eye on simple valve adjustment into the future. Thanks.
Always been a big fan of stihl products. Strange there was so much RTV in the crank but glad you were able to get it sorted out. Very interesting to watch!
I have a neighbor that owns a fs80r and I can say it's one of the hardest to get right carburetors I have seen on a stihl. It always reminds me of the old holley 4 barrel carbs when working on it every time you think you just about got it perfect and try to fine tune it just a pinch more, it decides to act like you suddenly turned the adjustments a mile out of adjustment. I can say they tend to like fairly high idol almost to the point of engaging the clutch, otherwise the trigger response will eighter suck or it will run lean at full throttle. Hope that helps and thanks for the entertaining video!
Great video! I was surprised to see that RTV in the engine. I bought a new FS90R years ago and after 2 years, it quit running. I also found RTV in the engine, holding the valves open. Cleaned it out and it ran for a while, then quit again. Took it apart and found more RTV. Cleaned it a second time and then got rid of it and went back to my Redmax trimmer from the 1980’s. I thought my experience was a fluke, but I guess not. Thanks for sharing!
i love seeing this stuff haha! it makes me want to go out and fix everything that uses a small engine on the farm haha! thanks for taking us along on this journey!
Yes I think Sthil quality is definitely going downhill recently. They want to decrease costs and raise prices in the last couple years. Hope they can turn it around and get back on track but they may be headed for a downfall like so many other brands have fallen victim too due to greed.
Great video! I have a Stihl 2stroke brush cutter but have just recommended a four stroke to a friend but with reservations because of that cam wheel. Not a big deal to replace though and your 'explain as you go' style is very user friendly! :)
Unless as he mentioned plastic was used on purpose to make this the sacrificial part. It will fail first before any other part is damaged thus protecting the whole engine. Plus it is easy to replace. Only issue if they are jerks and charge an arm and a leg for the replacement part when they DESIGNED it to break.
@@nostromo526 People just seem to assume that because something is plastic that it was made to be cheap, rather than for some other reason. Same people probably think the shear pins in the collapsible steering shafts should be steel instead of soft plastic :)
Excellent job sorting this. I had figured the piston was sticking in the bore, as I had that experience with a Sears four stroke weed eater. Piece of junk, but no plastic cam. Shame on Stihl for using plastic on a sliding friction surface. I've never seen another engine use it.
I was told by a lawn mower repair shop never use starting fulid in a motor that uses fule/oil mix, the reason is the cylinder walls are coated with Teflon and starting fulid breaks down that material making it soft so when the rings pass by the weak spot it tears it off the cylindef walls effectively trashing the motor.
It's an older unit. Using the correct oil, fuel mix has an impact on it. The fact that it took out the cam lobes and nothing else is actually a good thing, preventing much more damage and alerting you to a problem. We have the same engine in a pole saw, and it's seen ALOT of abuse. The cam has not worn out yet, but we did need to make a valve adjustment.
My 4 stroke Stihl has a oil sump, but I still put a small amount of oil in with fuel for extra lubrication. But I've never looked at the timing gear. Now you have sparked my curiosity.
Got the same unit - Love mine - sooo easy to start and love the fact it is a multitool (saves carrying many dedicated units or swapping between strim and brushcutting/edging/polesaw/mini rotovator- and packs away small enough to not be a hassle to store and transport) I replaced the 2 bushes the clutch pivots on as mine had got rusty seized/in a bad way (my clutch now works as intended without resorting to locktiteing them in a bit loosey goosey...I may have also replaced the spring at the same time) As soon as I saw the start of the vid I was screaming valve lash / decomp fail at the screen..amazed to see how worn away that cam got before things got noticeably bad LOL...I didn't see that one coming make sure the valve cover is well sealed - a leak here would also be bad and would cause running/mixture issues (they do a valve clearance kit, Stihl 4180 007 1005 - comes with a fresh gasket, feeler gauge and a fresh seal for the screw that holds the cover on...was not expensive and peace of mind there are no leaks up there - can be had for less than 50 UK pence IIRC) Have had my carb apart from the usual sin of storing with fuel for too long, no sign of RTV floaters - so maybe I got lucky and the tube at the factory was running low the day they put mine together :) Fab video as usual John
I have a small engine shop. I specialize in 4mix equipment. These only wear down like this when there's not enough oil or there's an air leak which causes oil starvation on the bottom end. Normally, the main wear on the cams is actually cavitation holes. Stihl originally tried several materials for these cam wheels and found that this nylon composite worked longer than the metal versions. By the way, the reason your clutch is acting up is because you didn't press out the bushings. They get rusted and expand. They aren't supposed to be tight.
I do field mowing & have 3 MS130 + 1 - MS90. They have thousands of hours trouble free mowing but.. .now the compression release is starting to fail on all of them. Better not....try to start-em unless held tightly to the ground. Snap-ouch- yikes!!!!
100 % agree with you about making your own , you definetly have the skill-set. It would make a good video too. I own the same weed eater/saw/bush cutter and would love to learn how to make my own. Certainly would make it last a lifetime. Awesome video. Please keep em coming.
My brother manages a large landscaping company. They switched from Echo to Stihl and back to Echo. The Stihl stuff was near constant carb issues, the Echo stuff just runs and lasts. This is a sample size of hundreds of pieces of equipment.
John, Taryl Fixes All just done a video about the Stihl 4 mix. There's a specific oil, (Not regular 2 cycle) oil that you're supposed to use in those engines.
I have a Honda and the cam is the same design, you don't have to mix oil with fuel it has an oil res with a rotor that whips air into it then the crank has a hole that draws the oil in with the pos and neg pressure, then pumps it through a reed valve into the cam area up into the valve cover and then drains back to the oil res. great videos you have a new subscriber.
Have exactly the same model and 2010 year of manufacture. No issues with it apart from erratic idling. Start it up and its ticking over way to fast activating the clutch, back it down to stop clutch biting and its fine till you leave it for a couple of weeks, then it wont idle at all till you increase it and it runs ok. Then a couple of weeks later, the clutch engages again...lol/cry.
Just from personal experience with the 4 mix engines, your low speed screw seems to be too rich (thats why your idle cant be reduced without it stalling), and your high is too lean, which is evident by the bogging when you load it down while trimming. The low speed should be set to maximize rpm at idle, adjusting your idle screw as necessary, then open it another 1/4 turn. Your high speed should be set to maximize rpm with a full length of line on the trimmer head, then open it another half turn or so and listen for a very slight rpm drop. This will provide the best torque for brush cutting. The FS and kombi 90 motors will hit the rev limit with a full head when the carb is set for peak power, but I go a touch richer.
That KM90 engine is absolutely the same thing as their commercial FS90/111/131 engines. They all have the same plastic cam gear. Their commercial/professional pole saws have the exact same plastic cam gear. All of the 4-mix engines have that same plastic cam gear. 10+ years of work and a $15 part seems like a pretty fantastic service life. I would personally like to see a metal one even if it made it a few ounces heavier. The "homeowner" kombi version is the KM56 which is a true 2-cycle so no plastic cam gear. I have a 13 year old FS55R (the older version of the 56) and it still runs like a brand new one. I haven't even replaced the spark plug in it. I just bought a KM131 and if it runs a decade and only needs a new cam gear eventually, I'm completely happy with that.
Thank you for the detailed video of what was causing the malfunction. I found this video very informative and really enjoyed the step by step process 👍🏻
This was my first video i saw from you, i really enjoyed the detail you were going into in the disassembly and reassembly and in the troubleshooting as well. Definately worth a subscribe!
The issue with your clutch is that the bushings in the shoes are seized. Press out, clean corrosion, little lubricant on bushings, reassemble, torque bolts fully.
I have a stihl 170 trimmer and after I got it home, I thought boy it pulls hard. I took it back to the dealer and they said that's how they are. So i messed with the timing and it is much easier to pull to start! I've had mine since 2014 and when it runs will cut weeds like crazy. Last year it started running not so good and I bought a new one a 90 or 91 can't remember but it is good enough.
As a Stihl dealer and small engine mechanic, I can tell you I have seen this all to often. Most of the time’s it happens because d valve clearance isn’t checked/adjusted often enough. I Alwas recommend to check the valve clearance at least annually. Ore the ,,hammering” of the those shoes that ride in the Cam, will destroy it…… The reason why they made it out of Plastic in the first place, is because of lubrication.
Greatings to you and anyone how reads this: Jan from Switzerland
PS: There may be some grammar error’s in this text, English isn’t my strongest language 😅
@Jan, I am not convinced of this explanation - why would hammering make it wear all the knob down in one catastrophic event as explained by Jon? It makes no logical sense.
I would suspect either lack of lubrication or over-heating. One could amplify the other. "Plastic" obviously does not support overheating together with mechanical stress.
Could misadjusted valves mean higher operating temperature?
Was the machine running extra hot when you used it Jon?
Sorry Still dealer but there is absolutely no reason other than cheap out (or turning more pieces per the same time spend to make one in Brass, since with injection moulding you can pump let's say 10 per cycle while you make one on a CNC) for that cam being made of plastic other than a metal.
Don't want to make it so good that it doesn't go bad anytime right, or the after sales would lose profit and new sales also drop since why I would buy a new one if my old 20 year something still runs like a champ?
Why would a company that has been the Mercedes of small industrial engine quality elect to build an engine with plastic cams? I have a 22 year old Ryobi 4 stroke 845r 25 cc 4 stroke engine that finally wore out after 22 years of pretty steady use and it wasn't the cam it was the flywheel, you cannot find replacements for these once the keyway wears out. Nowadays Ryobis have plastic cams and their cams are OHC where all the engine heat is, in the head. Why Stihl didn't take Honda's little GX 4 stroke engine tech to heart is a head scratcher. I also have a Honda GX31 pump engine I bought used in 1998 and it still runs like the day it was made.
@@heel57 Running lean cause of a chunk of rtv clogging the carb could cause it to overheat pretty quick.
I agree with ya bud i do think his oil has been pretty sub par aswell Small engines mech 30 years here. Normal ill see pitting and the comp release failed never seen a melted one that bad. In the fleet i work on we have 40 + of these units.
Love how you always diagnose unusual problems and explain why you are doing a particular "trial" in attempting to isolate the root cause of the failure.
Ummm I don’t think he found any roots causing the problem 😅😅😅
@@TomTom-tg2cb running lean could cause all sorts of problems. as does killing a saw with the choke because the killswitch does not work.
@@TomTom-tg2cb LOL 😅
In today's "throw away" mentality, I think replacing a $15 part on a 10 year old tool would definately be considered a WIN. Glad you were able to find the part and replace it easily. Thanks for posting!
Agreed. I think that is a great design feature.
Agreed.
💯 agree
As a fellow small engine mechanic it is def easier the only thing that's hard to trust is the after market carbs 😂
@@jomarcruz659 being a small engine mechanic, what do you think of how comically cheap the off shore carbs have gotten? I bought a couple that were less than $12, have had great luck with them (not to say they're all ok). I've even bought a carb that came with a tune up kit air/fuel filter, spark plug, fuel lines, etc for less than $20.
Even if they straight up copied the design, they still had to buy the stock, program and run probably 30+ cnc operations, assemble it, package it, warehouse it, advertise it, and ship it halfway around the world for less than what a subway sandwich now costs. It's just insane to me. I know labor costs are next to nothing over there, but holy crap.
About 20 years ago, I installed a new telephone system at Tecumseh's warehouse in Slough, UK... I was shown around, and was impressed by all the stock they held... Chatting with the boss of the operation, I was told that their mower engines were designed to last 100 hours at most... or two average years of garden mowing... shocking!
Diy electrical power tools are only expected to be able to do 16 hours work to be of "merchantable quality" ?
Lets not pretend like nobody saw the little bulldozer and and track loader in the outro. Are those future projects by any chance? Love your videos, you are doing a fantastic job.
Well spotted. 👍👍
In his winch video he also loaded like a six wheeled utility vehicle onto his trailer which I thought would be part of the future content.
Man I'm excited to see all 3 of those on the channel. I was stoked to see them
@@wg8304 It will. Just aren't enough hours in a day!
@@FarmCraft101 Hey, there's hours at night as well and sleep is over rated. 😁
This has to be one of my favorite small engine repair vlogs of yours. The instruction and explanations are invaluable to a novice small engine repair guy. Thank you. I learned a great deal.
That ad segment was actually pretty cool, it was really neat to be able to see the heat and thus the Work that the hydraulics are doing in the line.
Yep, this is an ad I'd watch. This and the ones by Aging Wheels.
Yes, actually enjoyed it.
The issue with the clutch is that the pins the shoes pivot on are rusted into the shoes, you need to punch out the pins and remove the rust to allow the shoes to pivot nicely.
You know that you love some FarmCraft101 when you see the notification pops up on your phone that a new video was posted. You park your tractor and head to the house to watch the new video. Not disappointed eighter, it's another great video.
This video was incredibly well done. I appreciated getting to see your entire diagnostic process and your skill in taking apart and reassembling all the parts. What I liked best is your ability to teach how each part functions as you went thru the process. Most of us would never have access to this level of expertise at our local small engine repair shops. Thanks so much.
I love your videos, but I especially like that you explained how the engine works. The compression release was quite interesting!
Always wondered how a compression release worked. Now I know, thanks.
Saw the cows around a brush fire, but no close up on Big Mama. How is her hip?
Got in one Seal camo, check.
@@markbrown6236 Big momma is doing well. Hip seems to be improving. Cheers!
Enjoyable, venture into a Sthil multitool. All these producks have a built in manufacturers end life. You have the confidence and skill to dismantle and rebuild, most owners do not . Result is machines get trashed and new ones are purchased. C’est la vie. Thank you.
I really like my Stihl equipment - have always been a Stihl guy, owned half a dozen saws and several trimmers including a 2 stroke kombi system setup. My only real complaint was the carb on my MS-180 saw, replaced it with one that could actually be tuned and it runs way better. The rest have been great. Their low end homeowner products are way better than any of the other low cost competitors!
Love your small engine videos. I've got a Craftsman 2cycle weedeater that is 30 years old and after replacing the fuel lines and tank filter and periodically adjusting the carb and greasing the cable drive, it still runs great.
Those old craftsmen products were awesome.
You are a very skilled teacher and every video you post is a wealth of knowledge. Always excited when you release something.
Jon, Thanks for the teardown, repair, and all the explanations! Always good and the viewer might even learn something they didnt know, as I did about the 4 stroke but mixed oil/gas. That cam was terrible, glad you got it fixed!
Have the exact same unit and around the same age. Thanks so much for documenting the maintenance and repair. I think I'll need to adjust my clutch like you did.
Ditto. I have the same one. So far mine “just works”. I’ll be on the lookout. Watching further into the video… ick. I’m not happy. I have 4 of the attachments in think. It’s really nice to only have 1 engine to maintain.
Great content, as always. It's very satisfying to watch you fix stuff and explain what is what.
I am a former Stihl dealer. In the 70’s and 80’s I don’t think that you could get a better quality unit. Sadly everything I have purchased in the last 10 years is plagued with problems that shouldn’t happen. Foreign material in the carburetors. Bad coils. Bad plug wires. Bad tank vents. On and on and on….. no more Stihl for me.
I'm with you, but what do you like instead? I'm not thrilled with Echo's build quality, either.
Echo and Husqvarna are worse. At least stihl is repairable
Holzfforma!
@@my_channel_44 lol, get outta here with your bing-bong saw
@@steve709061 DeReal, 20" $125.
Who bing bong now big boy?
Thanks for taking the time to video this. It was cool to see the breakdown and fix!
Great to see your process but you should check the hole in the cover plate where the cam gear shaft rides. It opens out letting the shaft wobble causing it to wear early. That's what happened to my 131 so I had to replace the plate as well.
It's impressive how much more joy you can get out of your work you can get when your tools are working correctly/well.
That's pretty interesting. I have a KM-56-R powerhead and those same attachments, plus an edger. It's a nice little system. The KM-56-R is a true 2-cycle, but I had to go pull the engine diagrams to confirm that. I never looked too closely at it because it's always just run :)
7/31/2024 one of the best teaching well done videos i have seen in years! Great video, great volume, not just a bunch of talking about it. THANK YOU!
That was very interesting indeed I have never seen a 4 stroke that runs with mixed gas. Thanks for sharing.
My dad has a troybilt tiller that has a two stroke, but runs on regular gas.
It has a oil tank that you fill everytime that you fill with gas.
It mixes the oil into the gas at the carburetor. It's weird.
Nice fix, the early honda gx25 engines had a similar problem when run to hot the plastic cam melted, they changed from gear driven to notched belt driven cam. Also Stihl uses they're own brand of Dirko sealant which is also orange (easily mistaken for rtv) but looking at the crankcase when you took it apart i'd say someone has been in there before, i've never seen Stihl use overkill amounts like that. When it comes to you're clutch there are crush tubes in the pivoting ends of the shoes that are frozen in place (hence clutch will only work with bolts loose) you need to free up those crush tubes in the shoes. if you leave it the way it is it will ware through the bolts and cause more damage!! Good luck with it, thanks for posting!
Nice video. Practical, helpful and with your usual sense of humor. While not rebuilding the boom lift hydraulics, this video was equally as interesting and probably more useful for us folks.
From my experience replacing that carb diaphragm that's a little stiff will help with engine performance and response. The clutch hanging up could have also contributed to the cam wear so fixing that should help. I have also noticed a difference when using Stihl's fuel or Aspen fuel vs. pump gas or other canned fuel, for what it is worth.
Looking forward to next week's video.
It doesn't make sense for commercial guys, but I only run Stihl gas. I don't worry about it sitting, things start and run fantastic on it. My 4 Stihl engines are going on 3-5 years old and all start with little to no fuss.
Have wondered about canned fuel (for a rarely-used engine or two, where reliable operation is needed.)?
I am an ASE Master Technician with decades of experience
and
I always learn something new watching your videos
Great job John! You are a constant inspiration to a mechanical hacker who can "almost" fix anything, well at least dismantle things properly.. I had a 4 stroke Ryobi back in the day that suffered a similar failure from a plastic cam melting down to round. Of course I instantly ditch it and used the excuse to buy a new 2 stoke Toro that is still going many years later. Didn't discover the real problem until my curiosity got the best of me and I took the old Ryobi apart. I was shocked to see the cam lobe was plastic and still to this day wonder what engineer thought that was a good idea. More likely to have been the result of the final design being re-engineered by the accounting department! Well done.
Perhaps they make them plastic to act as a sort of mechanical fuse. The cam lobe will reliably fail first and can be easily replaced.
Rough machining, heat treating and grinding a hardened steel cam would probably be one of the most expensive steps in making an engine like this. The plastic is adequate for most uses (so long as you don't overheat or over rev) and way cheaper to make because it can be produced by injection moulding.
Mr John your videos are some of the most informative on the internet. I work for a Stihl dealer and didn't know about the camshaft. We never get in to the engine that far. One of our stores work on all the units, I just do the small stuff. Thank you for the crash course in rebuilding the engine. Thanks for everything you do for the videos
I used to work with a light 2 stroke Stihl about 30 years ago. It was a brush cutter, not a combi tool. It was great! Also the duo handle bars on that machine work way better for the long term. But maybe not that handy when using the saw 😉 Great video.
Excellent video - thanks.
My main takeaway is that a key diagnostic to look out for is the engine being hard to turn over due to the compression release not working - if you have this symptom you might think it is normal and not think anything of it - that is what I did for a while as I was unaware of the compression release feature. So if you experience this then I would say it is definitely worth checking the cam - and specifically the little valve release lug shown in the video at 34:30 - and while you are at it, the valve clearances.
Fixing Stihl products is a hobby of mine. My gardener has the KM130R and had the metal plate on the back of the cam detach and disintegrate into two pieces with the little weight loose in the engine...also signs of melting. Surprisingly little damege - just the mounting point for the cam on the engine block where the pin goes in was quite badly worn and scored so I cleaned it up as best I could and then placed a 0.1mm shim between the cam and the engine block.
Hard to work out why the failure has occured as plenty of lube evident. I have the same model so decided to replace mine prophelactically - was worn down by 0.2mm, and the metal back plate seemed loose. (I also had a broken valve a couple of years ago, so have done the full engine tear down in the video.)
If you think about it, the valves only opening a tiny amount, they were basically acting as an artificial throttle. It was coincidentally just enough air/fuel to idle, but that’s it. You opening the throttle on the carb changed nothing, since it simply couldn’t breathe more than it could at idle.
What is odd to me is how quickly you report it happened. Maybe the cam somehow has a harder surface, and once it was compromised, the rest got lathed down really fast? Idk how that could be true with plastic, but I’m no polymer engineer, so I’ll leave it to others to figure that out.
Probably just overheated while in use and softened the plastic.
I have heard that the 2 stroke oil should be stihl
It's a failsafe feature. It's supposed to give you some indication of improper running, and needs maintenance. Saving on damage to the rest of the valvetrain. It's a common wear item, especially the compression relief. However, some of their 4mix engines, suffer from damage due to no rod bushings. Certain models have them, while others don't, leading to serious damage, and needing a complete engine. Which costs as much as buying a new piece of equipment. Go figure 😢
You are one of the few I watch 100 percent start to finish!!!
This is why most people just buy a new tool. I would never get all the parts back in place and eventually end with it in the scrap pile. Thanks for the tutorial & the explanation of all the functions. The camera angle was great. I was right up in there the whole time. Thanks!
This came out at a perfect time, my primer bowl on my FS 130R STIHL trimmer got a hole in it the last time I used it. I’m glad I didn’t use it to long. I don’t wanna melt the cam-gear!! By letting it run lean!! Thanks so much for your videos!! Thought I knew a lil bit, but learning a lot from you!! God Bless, stay safe out there!
Funny, I've got roughly the same combi unit here for the house, maybe a model or 2 newer but about the same.. always wondered why it randomly misfires with a heavy load on it (usually the blower @ full throttle), now I know it's got a nylon cam that's likely worn out. Learn something new every day! Caught a little foreshadowing at the very end too 😉
Its not a misfire. That is the rev limiter kicking in.
@@rivtool515 lol 😂
I tend to use separate tools for each job. My FS85r weedeater is still going strong, as is my chainsaw, blower and hedge trimmers. Love your channel.
I have the same thermal camera but from a different brand (vevor) and I love it. Its great for electrical work and unlike older ones the refreshrate is high enough to not bother you. Only downside is that when it changes thermal range it freezes for a bit and it does that quite often.
We use Stihl since at least 2001. We have multiple saws, Weadaeters/Brushcutters, hedgetrimmers and leafblowers. We never had any Stihl related problems, most of them were my dads and granddads user errors. So all in all we are quite happy with them. The biggest problem is that the plastic and rubber parts start to dissolve and dont work as intended
I have two FS90s (one in service, one not) that have the same engine. It's highly likely that I don't have nearly the same hours on either that you have on this unit, but this sure makes me want to take them apart and check on that plastic cam. Thank you for the in-depth coverage.
@AnabelleJoan I don’t DM scammers. Go take a long walk off a short pier.
The second time I saw this. I am fascinated with the 4 cycle engine, but using two-stroke fuel!!! I used to teach small gas engine repair in a Middle School. I never saw students (who usually did poorly inside the school in their regular classes), but gave full attention to their own old engine piles outside. Never ceased to get the parts together and running.
Thank you for this video, it was a pleasure to watch as always. The STIHL "4-Mix"-engine has a good reputation for being durable, small, light and powerful. The idea to get rid of all that oil-cycle-fixtures like oil pan, - pump etc. by just using 2-stroke-mixture is kind of genius. You can use the same fuel for 2- and 4-stroke-engines on your STIHL tools without the danger of damaging the 2-strokes and without the hassle of stocking different fuel cans for various tools. And the engine is lighter without the oil cycle apparatus.
I think that this engine looked incrdible well for 10 years of farm use. I personally never had issues with STIHL tools, but if you want to see flimsy engineering take a look inside the cheap chinese made garden motor tools for hobbyists.... I think that the plastic cam did exactly what it was supposed to: It's the weakest point in the mechanism but on purpose, because it fails in the case of under-lubrication first, throtteling the engine down and preventing further and much more costly damage. The gasket material in the engine was surely not intentional, but maybe it was hardening out or something so that this happened after so many years.
I still find it interesting that some say they notice a weight difference between mini 4 stroke and 4mix or 2 stroke engines. My echo PAS2620 and Honda HSS25 are similar displacements and feel very similar in overall weight and the Honda has an oil sump and the extra mechanics to use it at different angles. The Honda is relatively well balanced and quieter to boot compared to Stihl's 4mix. Same goes for the Echo, it's a touch quieter than the Stihl.
My buddy that works on small engines loves the stihl 4 mix, keeps him busy
When I checked my valves on my km131r I also have bits of rtv up in the valve cover and I think I had some in that carbs pulse line to but I can’t remember.
Always a good time when you've uploaded a new video. With this one I did cringe a bit the way you were turning those needle screws like there was no tomorrow 🙂 My experience is they need small adjustments, and wait a bit after each. It takes some time for the carburettor to respond. But other than that I'm impressed with the way you explain things as you discover them. Great job !
The zama carbs on the 4 mix don't react to the needles much, they have a fixed jet inside, so even a half turn only has a small effect on actual fuel delivered. These aren't like the needle metered carbs on older chainsaws.
Very informative. Thank you sir. As a veteran landscaper I recommend taking the guard off for longer string, better access, less weight and much faster work.
Ive used the Stihl 110' and 111's for a long time but a couple of years ago switched to echo 2620 model and wont be going back to Stihl. Much smoother trimmer.
Great video. We got a good lesson into the working of a small engine, a 🦭 and 🐄🐄🐄🐄 hanging out around a bonfire 🔥 👌
As Taryl recently said: it will all soon be batteries only.
However, this was a very well made and informative video. Reminded me of when I split my first chain saw wide open and replaced the crank bearings and piston rings ... about 40 yrs ago.
Great job and another tool saved from the land fill. I just wish they made a small prop head attachment, so I could attach it to my canoe.
Hi John I have a fs90r strimmer as well. I had problems with my cam as WELL, The housing you removed to gain access to the cam on my machine had wallowed out where the pin the cam ran on a nd the cam was knackered as well, and sticking clutch, the clutch shoes should pivot on the shoulders where the bolts go thru, the pivots are bad for seizing, thats why when you tightened the clutch shoe bolts they lock up. Your clutch bolts realy nead to be tight. These trimmers work good when all is good. KEEP UP THE GOOD FIGHT, love the vids
MAKE SURE you use the Sthl oil in those 4mix engines. They require special oil or you’ll wear the cam and the bearings early. There’s other videos on this subject.
Lies. Oil and fuel is just that. Higher or lower octanes and more or less oil is really the only differences you can make. Stihl oil when burnt burns almost to like a yellow o believe so if you use a different kind of oil in it when they check your warranty they look to see the oil you've been using has been burning yellow in the exhaust/muffler. They don't add some special additives or nothing it's just marketing.
@@shaynewalker4519 Maybe, but working on my BR600 is such a PIA, I'll use it on the chance it makes a difference.
@Steve just Steve never use ethanol gas and use 91 when mixing and you'll never have any issues starting or running and it can sit all winter pick it up next summer it'll fire right up. Non ethanol gas doesn't break down like corn gas does. And your fuel lines won't get brittle.
@@shaynewalker4519 it’s actually is very true. The 4 mix engines require some wear additives in the oil to help lubricate the piston pin bearing which in that engine is a normal bushing, not a needle bearing. It also needs the additives to prevent wear on the cam shaft. You are correct about the non ethanol gas though. My cheap Ryobi string trimmer starts on the first pull with ethanol free gas.
Which specific type of Stihl oil do you recommend for those 4mix engines?
I have a Stihl backpack blower along with about 12 other Stihl pieces of equipment. They all have great warranty. The blower just went in for minor repairs. 4 year bumper to bumper warranty. Outstanding
Great work! I always learn so much from you! And.. if one of those cows got much closer to the fire, y’all would have had some bbq for dinner! Thanks for all your content!
I picked up a broken FS-90 a few years ago which has the same exact power head assembly, someone had stepped on it and broken 2 of the tabs off of the bottom case which support the shaft so I had to do a full engine tear down to replace the broken stuff. My local dealer was really helpful, they sold me that $20 tube of OEM Stihl "Dirko HT" RTV to put everything back together and one of the repair techs warned me not to use to much like Stihl does sometimes because the pieces will eventually get into the engine and do exactly what you're repairing. Pieces get into the gap and wear down the plastic cam gear.
It needs more attachments like: socket adapter, gas powered flashlight, exhaust to leaf blower tube, cylinder honing jig lol
Nail gun, recip saw, sander… lol
Wow huge valve movement after gear change. Thanks John, I feel like I'm in shop class watching your videos. Learn so much.
That worn cam lobe is probably the result of a bad batch of whatever material it's made of. Reminds me of an issue Harley Davidson had with cam chain tensioners about 20 years ago. A number of engines grenaded because of it. Great eye opening video. I've always been a Stihl fan but from your experience and what I have seen on other channels, I may be changing over to Husqvarna.
Husqvarna make genuine 2 strokes, with much simpler carbs. I prefer them.
@@camo8768 I only wish that there were husqvarna dealers closer to me. closest one is 3 1/2 hours away. Same reason I opted to buy a 240r vs a 535ls
Well done. I just had a problem with the engine not starting easily and adjusted the valves. The FS 110 R runs really well now and starts with one pull after a simple valve adjustment. Like Jan said, I think maintaining proper valve adjustment is critical to not overheating and other operating problems. All good information. I will keep an eye on simple valve adjustment into the future. Thanks.
Always been a big fan of stihl products. Strange there was so much RTV in the crank but glad you were able to get it sorted out. Very interesting to watch!
I have a neighbor that owns a fs80r and I can say it's one of the hardest to get right carburetors I have seen on a stihl. It always reminds me of the old holley 4 barrel carbs when working on it every time you think you just about got it perfect and try to fine tune it just a pinch more, it decides to act like you suddenly turned the adjustments a mile out of adjustment. I can say they tend to like fairly high idol almost to the point of engaging the clutch, otherwise the trigger response will eighter suck or it will run lean at full throttle. Hope that helps and thanks for the entertaining video!
Video came out 26 second ago but see 5 comments from 1 day ago???
Patreon early access. Video goes up unlisted, Patreon members get links, then the video gets made public later.
@@Bobbias I knew something like that might be happening.
Great video! I was surprised to see that RTV in the engine. I bought a new FS90R years ago and after 2 years, it quit running. I also found RTV in the engine, holding the valves open. Cleaned it out and it ran for a while, then quit again. Took it apart and found more RTV. Cleaned it a second time and then got rid of it and went back to my Redmax trimmer from the 1980’s. I thought my experience was a fluke, but I guess not. Thanks for sharing!
4 mix just makes things excessively complicated for no reason.
i love seeing this stuff haha! it makes me want to go out and fix everything that uses a small engine on the farm haha! thanks for taking us along on this journey!
Yes I think Sthil quality is definitely going downhill recently. They want to decrease costs and raise prices in the last couple years. Hope they can turn it around and get back on track but they may be headed for a downfall like so many other brands have fallen victim too due to greed.
Great video! I have a Stihl 2stroke brush cutter but have just recommended a four stroke to a friend but with reservations because of that cam wheel. Not a big deal to replace though and your 'explain as you go' style is very user friendly! :)
You can point the temp indicator at the wife first thing in the morning to tell how your day is going.
Lol +1!!!
Thanks, It's fun hanging out on the farm. Big Thumbs Up.
Plastic cam, that's disappointing
But cheap!
Unless as he mentioned plastic was used on purpose to make this the sacrificial part. It will fail first before any other part is damaged thus protecting the whole engine. Plus it is easy to replace. Only issue if they are jerks and charge an arm and a leg for the replacement part when they DESIGNED it to break.
@@nostromo526 People just seem to assume that because something is plastic that it was made to be cheap, rather than for some other reason. Same people probably think the shear pins in the collapsible steering shafts should be steel instead of soft plastic :)
Great video as always. Thank you for turning down the volume on the noisey parts
Excellent job sorting this. I had figured the piston was sticking in the bore, as I had that experience with a Sears four stroke weed eater. Piece of junk, but no plastic cam. Shame on Stihl for using plastic on a sliding friction surface. I've never seen another engine use it.
I got this also but it is so hard to pull so i better check that compression release. Didnt know where it was so thanks for the info.
I was told by a lawn mower repair shop never use starting fulid in a motor that uses fule/oil mix, the reason is the cylinder walls are coated with Teflon and starting fulid breaks down that material making it soft so when the rings pass by the weak spot it tears it off the cylindef walls effectively trashing the motor.
It's an older unit. Using the correct oil, fuel mix has an impact on it. The fact that it took out the cam lobes and nothing else is actually a good thing, preventing much more damage and alerting you to a problem. We have the same engine in a pole saw, and it's seen ALOT of abuse. The cam has not worn out yet, but we did need to make a valve adjustment.
My 4 stroke Stihl has a oil sump, but I still put a small amount of oil in with fuel for extra lubrication. But I've never looked at the timing gear. Now you have sparked my curiosity.
Got the same unit - Love mine - sooo easy to start and love the fact it is a multitool (saves carrying many dedicated units or swapping between strim and brushcutting/edging/polesaw/mini rotovator- and packs away small enough to not be a hassle to store and transport)
I replaced the 2 bushes the clutch pivots on as mine had got rusty seized/in a bad way (my clutch now works as intended without resorting to locktiteing them in a bit loosey goosey...I may have also replaced the spring at the same time)
As soon as I saw the start of the vid I was screaming valve lash / decomp fail at the screen..amazed to see how worn away that cam got before things got noticeably bad LOL...I didn't see that one coming
make sure the valve cover is well sealed - a leak here would also be bad and would cause running/mixture issues
(they do a valve clearance kit, Stihl 4180 007 1005 - comes with a fresh gasket, feeler gauge and a fresh seal for the screw that holds the cover on...was not expensive and peace of mind there are no leaks up there - can be had for less than 50 UK pence IIRC)
Have had my carb apart from the usual sin of storing with fuel for too long, no sign of RTV floaters - so maybe I got lucky and the tube at the factory was running low the day they put mine together :)
Fab video as usual John
I have a small engine shop. I specialize in 4mix equipment. These only wear down like this when there's not enough oil or there's an air leak which causes oil starvation on the bottom end. Normally, the main wear on the cams is actually cavitation holes. Stihl originally tried several materials for these cam wheels and found that this nylon composite worked longer than the metal versions. By the way, the reason your clutch is acting up is because you didn't press out the bushings. They get rusted and expand. They aren't supposed to be tight.
Straightforward and easy to understand, great job!
Watching this video just answered all my curiosities on how these small engines work.
I do field mowing & have 3 MS130 + 1 - MS90. They have thousands of hours trouble free mowing but.. .now the compression release is starting to fail on all of them. Better not....try to start-em unless held tightly to the ground. Snap-ouch- yikes!!!!
100 % agree with you about making your own , you definetly have the skill-set. It would make a good video too. I own the same weed eater/saw/bush cutter and would love to learn how to make my own. Certainly would make it last a lifetime. Awesome video. Please keep em coming.
My brother manages a large landscaping company. They switched from Echo to Stihl and back to Echo. The Stihl stuff was near constant carb issues, the Echo stuff just runs and lasts. This is a sample size of hundreds of pieces of equipment.
John, Taryl Fixes All just done a video about the Stihl 4 mix. There's a specific oil, (Not regular 2 cycle) oil that you're supposed to use in those engines.
I have a Honda and the cam is the same design, you don't have to mix oil with fuel it has an oil res with a rotor that whips air into it then the crank has a hole that draws the oil in with the pos and neg pressure, then pumps it through a reed valve into the cam area up into the valve cover and then drains back to the oil res. great videos you have a new subscriber.
Dude! I’m really liking these 4 mix engines. 4 stroke performance with minimal maintenance (no oil changes). I might have to invest in one of these!
There are bushing in the clutch shoe that need to be pressed out and cleaned for good clutch engagement. Really enjoyed the clip, keep um rolling !
Thanks!
Fantastic video! I love small engine repair, and being a loyal Stihl guy, this is even better!
I bought a KM131 combi last year, i like it a lot and found the attachments from my old craftsman combi system fit it well enough.
Have exactly the same model and 2010 year of manufacture.
No issues with it apart from erratic idling. Start it up and its ticking over way to fast activating the clutch, back it down to stop clutch biting and its fine till you leave it for a couple of weeks, then it wont idle at all till you increase it and it runs ok. Then a couple of weeks later, the clutch engages again...lol/cry.
Nice video! My decade old KM 90r just bit the dust, after watching your video, im gonna dig into it
Definitely one of the best videos published. The attention to detail is much appreciated.
Just from personal experience with the 4 mix engines, your low speed screw seems to be too rich (thats why your idle cant be reduced without it stalling), and your high is too lean, which is evident by the bogging when you load it down while trimming.
The low speed should be set to maximize rpm at idle, adjusting your idle screw as necessary, then open it another 1/4 turn. Your high speed should be set to maximize rpm with a full length of line on the trimmer head, then open it another half turn or so and listen for a very slight rpm drop. This will provide the best torque for brush cutting.
The FS and kombi 90 motors will hit the rev limit with a full head when the carb is set for peak power, but I go a touch richer.
That KM90 engine is absolutely the same thing as their commercial FS90/111/131 engines. They all have the same plastic cam gear. Their commercial/professional pole saws have the exact same plastic cam gear. All of the 4-mix engines have that same plastic cam gear. 10+ years of work and a $15 part seems like a pretty fantastic service life. I would personally like to see a metal one even if it made it a few ounces heavier.
The "homeowner" kombi version is the KM56 which is a true 2-cycle so no plastic cam gear. I have a 13 year old FS55R (the older version of the 56) and it still runs like a brand new one. I haven't even replaced the spark plug in it.
I just bought a KM131 and if it runs a decade and only needs a new cam gear eventually, I'm completely happy with that.
Thank you for the detailed video of what was causing the malfunction. I found this video very informative and really enjoyed the step by step process 👍🏻
This was my first video i saw from you, i really enjoyed the detail you were going into in the disassembly and reassembly and in the troubleshooting as well. Definately worth a subscribe!
I think the attachment engages very easy because you use the loctit on the screws for the clutch and didn't tighten them a the way up
The issue with your clutch is that the bushings in the shoes are seized. Press out, clean corrosion, little lubricant on bushings, reassemble, torque bolts fully.
I have a stihl 170 trimmer and after I got it home, I thought boy it pulls hard. I took it back to the dealer and they said that's how they are. So i messed with the timing and it is much easier to pull to start! I've had mine since 2014 and when it runs will cut weeds like crazy. Last year it started running not so good and I bought a new one a 90 or 91 can't remember but it is good enough.
Great work, i like u approach to problems solving!