I've watched several of your videos to diagnose multiple issues on my cb750. You've not only corrected the issues, but have made my bike run literally like it's new. Keep up the good work and thank you!
I know this is like 12 years later but I have the same exact motorcycle with the same exact problem. You are a true godsend man and you don’t know how much I appreciate you making this
Thanks for the awesome video! My father in law has an LTD 440 with the same symptoms that I told him I'd take a look at for him this winter. This will be extremely helpful. Thumbs up and subscribed!
Ace! After a recent top-end rebuild, my bike has had the craziest, most inconsistent idle and idle screw doesn't seem to make a difference. Probably didn't put a hose and/or clamp back on correctly. Cheers for posting this. Genius idea, sir. Many thanks.
@vasylivy To help illustrate my point, take out the air filter in your bike and see how it runs. Even with the benefit of all carbs running equally lean (as opposed to just one leaking carb-airbox boot) the increased airflow will still create a lean mixture. This is why re-jetting is so important after adding pod filters... if increased airflow before carbs had no effect on lean mixture, then all you would have to do is dial down your idle screw after adding pods
Great vid. Had a problem with my bike, thought i would use youtube to see if I can find a solution to my problem. Your vid was the first vid I watched and I got my problem solved. Thank you
Sir, Dude, Dudorino if you're into the whole brevity thing. You are awesome! Thanks for all you videos. What you do by making these videos is everything that is right with the world.
Hey Max. Keep up the great videos helping out us less mechanically inclined people :) I have a 2002 Honda Shadow Ace 750 that sat for two years in my garage. I had someone clean the carbs, I cleaned the fuel tank put new oil, plugs, battery,fuel filter and fresh gas and the bike starts up and idles fine but stalls if I touch the throttle. I used your techique with carb cleaner and seems I have an intake leak because the idle will increase and smooth out for a few minutes every time I do this.
Thank you I had the same problem I never thought of putting a boot over the intake connection, I sprayed starting fluid right on that spot and the engine rpms raised. but have been unsuccessful at stopping the leak but I believe you gave me the solution thanks for the video.
Just a note that may help a few that have a need for a Quick fix for old cracked rubber intake boots.....3M polyurethane windshield sealant. It is black and Seals all cracks and leaks it seems to vulcanize to the rubber better than silicone . And for The guys that pull the baffle need to pull the main needle on the throttle slides and move the clip 2 or even 3 clicks to the bottom of the needle to fatten up the mixture in transition from idle all the way to full throttle. It will be an immediate differnce in the way it responds from idle. Has worked for me for over 40 years.
I have a '79 GS 550L that I'm fixing up. Got it running better than when I bought it but at about 60% throttle it flattens out and dies back down. I'm going to check for a vacuum leak today but I'm thinking I need bigger jets to go with the new pod filters I put on. My carbs are Mikuni Kogyos and I was wondering how do I figure out what size jets to buy. I'm addicted to your videos and really appreciate the help. You're doing an amazing job and a great service!
thanks for all these videos! on my 83 CB650 I'm trying to find out how to reconfigure my carbs after cleaning them. are pilot screws typically screwed in all the way? the fuel/air screw (with the tiny washer and o-ring) is 3 turns out?
Welcome to Canada! Home of good social services and high prices. LOL Price includes shipping, rings and clamps. Thanks tons for all your videos I am new at this and they were a big help.
Yeah it is, it causes the air to come in to be full of vortexes which is very disorganized compared to the nice smooth stream coming from the airbox, and therefore is less efficient at picking up the gas molecules to be burned in the engine
The tube hanging down is probably an overflow tube, in which case yes it should vent to the air. If you have very poor condition airbox boots they may leak air which could lean out your mixture. However a bike that performs well on the flat but bogs on hills is a classic sign of float levels being off, because the gas level in the float bowls will flow to the side of the bowls on an incline and either enrichen/lean out the mixture. Check the floats
If you ont find any vacuum leaks, then things are tightened up properly. However you might have some disconnected vac lines, loose air box, air filter not mounted properly, etc. Thats just for vacuum leaks, many other things can cause idle issues too, like clogged jets, sticky slides, float level to high or low, etc....
@ilikesuzuki There are a couple of ways to tell. You can look for some thin black smoke out the tailpipe, that indicates a lean mixture, as does black sooty deposits on the spark plug, or if when you put on the choke the bike dies. If you are burning too lean, then your spark plug will look ashy an whiteish. Its possible you may have a fuel flow problem, partially clogged main jets, carb slides that dont go up all the way, some small vacuum leaks, or other problems.
@bghauck If I recall it should be located between 2 of your carbs, either pointing front or back, a small knob about the size of a nickel. But I could be wrong, I sold my v65 over a year ago. Go to bikebandit and look up your bike, if you click on the carburetor schematic it will show all of the individual parts to your carbs and you should be able to identify it for your bike.
Great video - another one of yours on how to free a stuck engine allowed me to resurrect my seized Suzuki Dr200se. I'm struggling with a surging issue on my '88 KLR650 - I've gone through lots of possibilities and ruled out the petcock, air/fuel screw, needle, enricher. I now suspect I've got some air coming in to one or more places, starting with checking the boots. Going to pick up some starter fluid tonight. Thanks for the clarity and straightforward approach in your vids.
Thank you for your many older bike videos. I own a 1978 Suzuki GS 750, which is in really good shape. 27 years of loyalty. Vacuum leak video helped me so much. I pulled the carbs could but not remove the manifold boots due to the bikes age, heat, PB, impact wrench, etc. Sprayed the boots with silicone, problem gone
I have a 94 Suzuki DR125SE. On idle it revs higher and higher gradually on its own. Also, when I open and close throttle it stays at high rev and takes forever to come down. I have checked the throttle cable, boots for vacuum leaks, adjusted the air/fuel screw on the carb, even changed carb to a totally new one and the problem still exists. The spark plug is black so I assume it's running rich. However, playing with the carb didn't seem to fix anything. It starts just fine. I have not looked at valve clearance yet but not sure if it's got anything to do with this. Any advice is appreciated
Valves would be a good thing to check, the replacement carb you put it, was it one of those cheap chinese ebay carbs? Those actually work surprisingly well in small motors, but you need to doublecheck that the jets are the correct size, sometimes they sell those advertising that the housing will fit a variety of engines, but jet sizes can be different. Look up the stock setting for your jets and confirm. Also put the air/fuel mixture back to stock, confirm that your idle knob and choke are set appropriately, and that you have a new air filter
I have the same bike and am having the same problem. Cleans the carb today and put it back on and now it runs just like you said in your comment. My boots are really shit and cracked so I'm hoping boots are the problem for me. Going to replace them and see if the problem goes away
1978 GS750 I rebuilt the carbs, head and valves machined, installed new rings, electronic ignition, chain and sprockets and new carb boot o-rings. It ran well except at full throttle. The fuel petcock also would not work except on prime. I did vacuum test but the idle did not change. I found some very tiny cracks in the carb boots after smearing them with RTV the issues disappeared. I think the vacuum issue only manifested at full throttle. Just food for thought. Thanks for your video
Great video i did it yesterday as i had my homemade manometer hooked up. Two of the airboots on my 94 ZX6R was leaking. Im replacing all four of them for a crazy price of $65..
@lauriejennifer It still sounds air/fuel related to me. What kind of bike are we working on here anyways? Does it crank up well and pull hard and even? Float set appropriately? Petcock delivers fuel well? Air filter mounted properly?
If you can get it to seal, which may be challenging, then it should hold up to the heat for a decent amount of time, if you are talking about the carb-airbox boots. The carb-engine boots wont hold up very long if they are radiator hose
@Michiganborn1969 Well those numbers sound about right, but they do not test the coil. You can use your multimeter to test the ohm resistance in your coil, check out your owners manual for the specific ohm readings you should experience. It can be difficult to assess for this problem with the bike warm, unless you warm up your bike and then real quick check continuity with the coil hot. What I do tho is just keep a bunch of spare coils on hand to swap out and see if the problem improves.
Ok I understand many people call the pilot screw and the air/fuel screw the same thing. That should start at about 2.5 turns, depending on your manual. Your pilot JET is inside your carbs, and it should be firmly seated, but not excessively so. Finger tight is just fine
Yeah vacuum leaks are when air from the outside are pulled into the carbs or manifold. However some leaks need to be repaired by replacing the boots, and often you do need to pull the carbs to replace them
The low ignition is the point, it means that it can help you detect even a small leak since it is so highly combustible, and even a very small amount will raise the RPMs. And no it no longer damages the upper end like older starting fluid did, because most fluid made today is made with cylinder and upper end lubricant. Carb cleaner is not as combustible so it is not as good at detecting leaks, although it still is somewhat effective
@scrambler250r Unfortunately Im not familiar with many gocart setups. Try seeing if there are adjustment nuts to tighten your cable, or if they cable is very old, it might have stretched and needs to be replaced
Right on always good to meet someone in the area, even if we are moving to Cali in 3 mos. If you ever make it down this way lemme know. Hey you want some competition cams for that kz1000? I got a set Im never gonna do anything with
@vasylivy Besides the fact that your engine wants clean filtered air, if there is a leak the air can come in much faster than normal, thus leaning out the mixture. The air filter retards the air flow down to normal settings, so it is important for all air to travel thru the filter first or else it will run lean.
Subscribed :) I've only had this bike since last October & my 1st street bike since 1993. I'm still learning where everything is at & how to fix/replace things. I don't want to sound like a dummy, but is the coil located where the other end of the plug wires go under a silver casing mounted on the head tube under the gas tank? If it s the silver box then I should also replace the plugs/wires while I'm at it b/c of mismatched plug wires.
Yes vacuume leaks around the boots were the problem, I filled them up with a little gasket maker. Not a very good repair, but good enough. Best to replace the boots.
Hey Leonard yeah first thing to check would be vacuum leaks. Also check that your petcock is giving good fuel flow, float heights are set properly, and that your float needles are clean. Watch my video on how to repair a nonrunning motorcycle for more ideas
Thank You for the informative video.. I recently got a 1978 hondamatic cb750a and have the same problems..the bike ran great about 1 year ago then it sat in someone's back yard..right noe the bike idles normally, but in order to start it i had plug up what i think was a vaccum hose and have the choke up..going to try your technique asap! Are all vacuum leaks predominately outside, or would i have to take the carbs off? i wouldn't really want to try that on my own kind of new at this whole thing.
thanks saw those but while tempted as they are the same age and millage of my failed ones I reluctantly opted for new. Can only face taking these carbs off one more time this year!
@mrmaxstorey thanks alot for the videos it's very helpful. i have a question for u. how can you tell if a bike is running rich or lean. for me my bike feels like when i go 65 mph plus it feels like it's loses a little bit of power? what do you think.
@bghauck Sounds like you are on the right track. Have you tried syncing the carbs? And might be a simple suggestion, but have you tried just increasing the idle via the idle adjust knob?
@mrmaxstorey I think that's why a surprising number of them are still around, and with such high mileage. Plus, Kawasaki is pretty good at not adding frivolous complications. They don't tend to have electrical problems, etc., as a result. I may be biased, though. ;-)
Id start by cleaning the carbs, replacing the air filter, and setting the float heights appropriately. All of those processes are demonstrated in videos I have put up on my channel
Sometimes you gotta clean them a couple times to get it right. Check float heights too, check that your plugs are not fouled and your idle screw is set right
Thanks for posting. I have KZ 440 that is having that exact same problem. Once it's warmed up it runs ok. But starting it I have that same problem to a tee. I thought it was a issue with the jets. What did you use to seal it up?
Great video. I am having a similar problem with the same bike. I bought new boots, and I'd like to replace the screws that hold them in (heads are all pretty destroyed) Is there a certain material screw necessary, as I tried using some spares that were lying around and they wouldn't quite tighten down the whole way? They are the same length and thread (6mm I believe) I am going to use this test today, could use your help though in the fix! Can I seal the boot to the engine intake with RTV?
Yeah it looks like the left one is too fouled to spark properly, I'd recheck that float height and also recheck the jetting on that one, its running rich for some reason. Valves are a great idea to check, you can get a compression tester form ebay for $15, won't be the best but it can get you in the ballpark
@edempsey3 Typically if you modify your bike with pod filters, you will want to increase your stock main jets by 2.5. So if you are running 100 mains, throw in a set of 102.5 and see if that gets you closer to where you need to be. Good luck on your project, and thanks for watching!
@mrmaxstorey Its funny you mentioned checking the charging system b/c I just bought my 1st multimeter yesterday to see if there was any issues. With key off the battery was putting out about 12.8V, key on about 12.3V, running @ idle about 13V & reved @ 3500 it hovered about 14V. But this test was all done within 3 minutes. I will try again after a d mile ride & see what reading I get then. The light do dim when I use ether brake or turn signals. Thanks for the reply..... Joe
Hey Max, I remember you saying in another video that you used your vacuum pump (the one for bleeding brakes) to also diagnose carburetor vacuum leaks. Could you possibly explain briefly how you do that? Because I just got my hands on a shiny new Mityvac to bleed brakes and would like to get the most out of the tool. Thanks man, keep up the good work!
@mrmaxstorey KLX 250 (actually, a 350 now). Not sure how to check float. Had a pinched fuel line before from the reserve tap, so it would die when switched to reserve. I already replaced and double-checked that fuel line and it is flowing properly. Not sure how to check either float or petcock. I use opaque fuel hose. How do you see if it's running without spraying gas everywhere? lol
Could be a number of different things. Vacuum leak like in the video, maybe a partially clogged carb jet, or the idle is just turned down too low on your idle knob.
You can get rubber pipe couplings in the plumbing section at Home Depot for $5. From the looks of it, you could cut one coupling in half and use it for both carbs. You can catch them on sale and buy a few different sizes. They come in handy.
Hey i have an old bike not sure what type, but its about 1980's. I have had it sitting for 6 months now and after i got it out a few days ago i have been struggling to get it started. It is just a little 70cc scrambler, but it was a lot of fun and just wondering if you could help. I cleaned the carb, but still just doesn't fire. Any idea's? Thanks and great video!
Just found your video and I think I might have a similar problem, so maybe you can confirm. Kawasaki Vulcan 800A with 2 cylinders, sometimes (1-2 times a month) after you start it with choke and the engine gets a little hot, it dies and fuel starts leaking from the carb. You can only start it after that by acceleration at 3-4000 rpm. If you run it afterwards, fuel won't leak, only when you stop and try to keep it in idle state (it will die if not accelerated). Thank you for your time and video, I'll check the vacuum system. Have to mention that the carb it's serviced and clean.
Its time to clean those carbs again, and this time put in an inline fuel filter between the petcock and the carbs. You may have a little grit in your tank which keeps getting into the carbs, causing one float to stick open or one of the float needles not to seat properly. Any time your carbs overflow its not a vacuum leak problem, its a carb problem. I have a couple videos up on how to clean the affected part, and how to set float heights. Good luck
@@mrmaxstorey So inline fuel filter. Also forgot to mention that after it leaks and I run it for 20-30 km at high rpm 3500-4500 then it comes back to normal, no more leaking. Those Kawasaki model carbs have some rubber on the carbs needle which makes them close pretty good.
Yeah most carburetors have that rubber tip, but if you have a tiny piece of sediment it could be as small as a grain of sand, it will cause the carb to overflow. The vibration of the motor from you running it at speed will temporarily dislodge it, but it finds its way back over time and overflows again. Clean the carbs, set the float height, and put in a filter. Done
No, I installed a new petcock kit as well. As soon as I siliconed the boots and the air box boots the running lean and the petcock issues disappeared. I suspect that the vacuum leak was only an issue when the carbs were sucking at full capacity. Anyway I am now confident enough that boots were an issue to spend the $150 on new ones.
Well a lot of motorcycle shops will sell air filter foam by the foot, you can buy some and make your own, although they often are only a temporary fix. To do that bike right you should really find an air filter that fits it properly
hey Max long time to hear im back in Germany after long time on the road and no internet and no driving in Cali :) i now got a Yamaha VX 750 and its my first twin V :) I hope your doing good bro!! and i got a question cause if anyone knows you probly do, what the best way to plug the card sync holes(ont the carb boots) cause theres a couple caps missing and whatever i put on em shoots right off and those caps are expensive so u got a cheap fix?!!! Did u ever come out with that Iphone app?
Thanks. Since motorcycle shops here in Northern California charge $90/hr I can't afford to take it in & I need to try to get this machine running as smooth as possible b/c I just have a permit to ride for now. But when it come time to take my safety & skills test I don't want the bikes performance to be a reason why I flunked the test for my endorsement.
Great video. Was wondering what "redneck repair" method you used? I've ordered some new carb holders and was wanting to ride in the mean time. I tried super glue, and it seemed to work with one of the carb holders....
I just fill the cracks with RTV and then run the bike so the vacuum sucks the wet sealant into the cracks. However no I dont seal up where it meets with the carbs, the clamps should be able to do that
@Michiganborn1969 It couldn't hurt to test it out, perform the test twice once with the bike just started, and once while warmed up. Also consider looking to your electrical system, especially coils. Old coils can develop hairline cracks which are not so much of a problem cold, but they expand when the bike warms up, and the spark cannot arc the fracture, grounding out. Check out my other videos for more diagnostic ideas.
Intake boot vac leaks are a good thing to check first, as it is an easy test. However, clogged pilot air circuit will produce similar symptoms as far as a no idle condition goes. If your bike checks out ok on the vac. test, but only runs with choke on, check the pilot circuit. Just my experience, but has happened more than once.
Right on make sure that that all your boots are tightened up and that they are not cracked. Also make sure that no vacuum lines are disconnected, and that the air box and filter are installed correctly
@TheDriftjockey I only use starter fluid or propane. Some guys use wd40 but I dont think it gives as good results because it is not as combustible. Other guys shoot water and wait for the bike to run worse, kind of the same idea but a different take on it. I don't do this because bikes with vac leaks run pretty poorly as is, so it can be harder to tell the difference.
@mrmaxstorey I should have explained better. It pulls in, it just doesn't disengage & then the cable won't pull back. Have you ever had the cover over the clutch mechanism off? It's so pose to push in disengage it right? Just trying to understand how it work so I know I've got it right. Thanks.
@mrmaxstorey Well, it wasn't the vacuum leak. Just checked. And I even tried opening the gas cap, as a shot in the dark. No change. Idle still wanders. Races, then doesn't, then does again, etc. Eventually, if i leave it idling, it will bog lower and lower until it dies. This happens sooner once the engine is warmed up. Almost as soon as I pull the clutch in to coast, it will bog and die. Frustrating. Praying it's not electrical...
hi max i did these checks today and found a crack in the air box and i welded it and i rechecked my air filter which was ok, the bike has improved altho it still does a little rev after i give it a rev ... i have bench sync the carbs with a needle.. would it run better if i got them syncernised properly? also it would run idlol for a good while then just die, it would start back up again with no delay thanks for your help philip
No, vacuum leaks only occur around the intake. If you have a leaking head gasket that is something else, causing low compression. However oil leaks around the magneto or the valve cover won't cause vacuum leaks
I am sorry but you are mistaken. Vacuum leaks at any part of the intake can cause running difficulties, especially in bikes with smaller cylinder displacement and bikes which are particularly high revving. If you take the air filter out of a motorcycle it will run very lean, the air flow will be disrupted with vortexes and eddies that reduce combustion efficiency, the bike will run hot and all kinds of stuff will get in the engine. Some bikes can still run without, but definitely not as well
ok so i have an 88 kdx200. erratic idle and revs pretty high. could the vacuum leak be in the engine itself? noticed a little oil on the cylinder base and a wee bit around the magneto. i cleaned carbs, replacing petcock, lowering air pilot to a 45, adjusted throttle cable...not sure what else it is, so replacing these gaskets could be the answer-yes??...good vids
@OldFordsRun Squirt some pb blaster or wd40 around the carb boots, then heat them up with a hair dryer. The rubber should get more pliable as the lubricant expands, freeing them
Thanks, I was able to tighten the intake manifolds and it appears to have solved that problem but now the bike will start and idle better however dies with any throttle. I turned the key on a few times with my ear and hand on the fuel pump and it doesn't seem to come on at all so i removed the fuel pump and put a jumper on it and it kicks on but I don't think it works on the bike. I have to charge my battery and see if it's not putting out enough to run the fuel pump. I'm lost lol
Commonly, guys will replace those old screws with allen heads for ease of access, Im not sur eif there is enough room to get a socket on a hex head down in there. As for the correct sealant, I typically dont use any if the rubber is good, but I always check for vacuum leaks after installation. Some guys use rtv or other stuff, it depends on your preference. You arent going to hurt anything by using rtv, just let it set before running the bike because heat, vacuum, and gasoline will corrode it
I've watched several of your videos to diagnose multiple issues on my cb750. You've not only corrected the issues, but have made my bike run literally like it's new. Keep up the good work and thank you!
Glad to help
I know this is like 12 years later but I have the same exact motorcycle with the same exact problem. You are a true godsend man and you don’t know how much I appreciate you making this
Glad to help bro, and I hope you get it sorted out
Fuck spending thousands in mechanic school when you can watch videos like these posted by fellow youtubers spreading knowledge for free
Beer Drinker lololol
Thank you so much! Finally fixed my bike after watching your video and seeing my bike had the exact same problem! I am forever in your debt my man.
U fam Bru inni
you, sir, are a genius.
Thanks for the awesome video! My father in law has an LTD 440 with the same symptoms that I told him I'd take a look at for him this winter. This will be extremely helpful. Thumbs up and subscribed!
Ace! After a recent top-end rebuild, my bike has had the craziest, most inconsistent idle and idle screw doesn't seem to make a difference. Probably didn't put a hose and/or clamp back on correctly. Cheers for posting this. Genius idea, sir. Many thanks.
Man your explanations are extremely clear
@vasylivy To help illustrate my point, take out the air filter in your bike and see how it runs. Even with the benefit of all carbs running equally lean (as opposed to just one leaking carb-airbox boot) the increased airflow will still create a lean mixture. This is why re-jetting is so important after adding pod filters... if increased airflow before carbs had no effect on lean mixture, then all you would have to do is dial down your idle screw after adding pods
Great vid. Had a problem with my bike, thought i would use youtube to see if I can find a solution to my problem. Your vid was the first vid I watched and I got my problem solved. Thank you
Sir, Dude, Dudorino if you're into the whole brevity thing. You are awesome! Thanks for all you videos. What you do by making these videos is everything that is right with the world.
Hey Max. Keep up the great videos helping out us less mechanically inclined people :)
I have a 2002 Honda Shadow Ace 750 that sat for two years in my garage. I had someone clean the carbs, I cleaned the fuel tank put new oil, plugs, battery,fuel filter and fresh gas and the bike starts up and idles fine but stalls if I touch the throttle. I used your techique with carb cleaner and seems I have an intake leak because the idle will increase and smooth out for a few minutes every time I do this.
Great video an good advice. Ive never considered using propane. Ive worked on small engines for years an I always enjoy a decent how to.
Thank you I had the same problem I never thought of putting a boot over the intake connection, I sprayed starting fluid right on that spot and the engine rpms raised. but have been unsuccessful at stopping the leak but I believe you gave me the solution thanks for the video.
This has helped me identify the issue with my bike that I’ve had since late January 😢 thank you 🙏
Glad to help bro
Just a note that may help a few that have a need for a Quick fix for old cracked rubber intake boots.....3M polyurethane windshield sealant. It is black and Seals all cracks and leaks it seems to vulcanize to the rubber better than silicone .
And for The guys that pull the baffle need to pull the main needle on the throttle slides and move the clip 2 or even 3 clicks to the bottom of the needle to fatten up the mixture in transition from idle all the way to full throttle. It will be an immediate differnce in the way it responds from idle. Has worked for me for over 40 years.
I have a '79 GS 550L that I'm fixing up. Got it running better than when I bought it but at about 60% throttle it flattens out and dies back down. I'm going to check for a vacuum leak today but I'm thinking I need bigger jets to go with the new pod filters I put on. My carbs are Mikuni Kogyos and I was wondering how do I figure out what size jets to buy. I'm addicted to your videos and really appreciate the help. You're doing an amazing job and a great service!
thanks for all these videos! on my 83 CB650 I'm trying to find out how to reconfigure my carbs after cleaning them. are pilot screws typically screwed in all the way? the fuel/air screw (with the tiny washer and o-ring) is 3 turns out?
Good simple demonstration, exactly what I was looking for.
Welcome to Canada! Home of good social services and high prices. LOL Price includes shipping, rings and clamps. Thanks tons for all your videos I am new at this and they were a big help.
Yeah it is, it causes the air to come in to be full of vortexes which is very disorganized compared to the nice smooth stream coming from the airbox, and therefore is less efficient at picking up the gas molecules to be burned in the engine
The tube hanging down is probably an overflow tube, in which case yes it should vent to the air. If you have very poor condition airbox boots they may leak air which could lean out your mixture. However a bike that performs well on the flat but bogs on hills is a classic sign of float levels being off, because the gas level in the float bowls will flow to the side of the bowls on an incline and either enrichen/lean out the mixture. Check the floats
@PinpointR Not necessarily. You could also have vacuum leaks, a weak spark, or even poor compression
If you ont find any vacuum leaks, then things are tightened up properly. However you might have some disconnected vac lines, loose air box, air filter not mounted properly, etc. Thats just for vacuum leaks, many other things can cause idle issues too, like clogged jets, sticky slides, float level to high or low, etc....
@ilikesuzuki There are a couple of ways to tell. You can look for some thin black smoke out the tailpipe, that indicates a lean mixture, as does black sooty deposits on the spark plug, or if when you put on the choke the bike dies. If you are burning too lean, then your spark plug will look ashy an whiteish. Its possible you may have a fuel flow problem, partially clogged main jets, carb slides that dont go up all the way, some small vacuum leaks, or other problems.
@bghauck If I recall it should be located between 2 of your carbs, either pointing front or back, a small knob about the size of a nickel. But I could be wrong, I sold my v65 over a year ago. Go to bikebandit and look up your bike, if you click on the carburetor schematic it will show all of the individual parts to your carbs and you should be able to identify it for your bike.
Great video - another one of yours on how to free a stuck engine allowed me to resurrect my seized Suzuki Dr200se.
I'm struggling with a surging issue on my '88 KLR650 - I've gone through lots of possibilities and ruled out the petcock, air/fuel screw, needle, enricher. I now suspect I've got some air coming in to one or more places, starting with checking the boots. Going to pick up some starter fluid tonight. Thanks for the clarity and straightforward approach in your vids.
Thank you for your many older bike videos. I own a 1978 Suzuki GS 750, which is in really good shape. 27 years of loyalty. Vacuum leak video helped me so much. I pulled the carbs could but not remove the manifold boots due to the bikes age, heat, PB, impact wrench, etc. Sprayed the boots with silicone, problem gone
I have a 94 Suzuki DR125SE. On idle it revs higher and higher gradually on its own. Also, when I open and close throttle it stays at high rev and takes forever to come down. I have checked the throttle cable, boots for vacuum leaks, adjusted the air/fuel screw on the carb, even changed carb to a totally new one and the problem still exists. The spark plug is black so I assume it's running rich. However, playing with the carb didn't seem to fix anything. It starts just fine.
I have not looked at valve clearance yet but not sure if it's got anything to do with this.
Any advice is appreciated
Valves would be a good thing to check, the replacement carb you put it, was it one of those cheap chinese ebay carbs? Those actually work surprisingly well in small motors, but you need to doublecheck that the jets are the correct size, sometimes they sell those advertising that the housing will fit a variety of engines, but jet sizes can be different. Look up the stock setting for your jets and confirm. Also put the air/fuel mixture back to stock, confirm that your idle knob and choke are set appropriately, and that you have a new air filter
I have the same bike and am having the same problem. Cleans the carb today and put it back on and now it runs just like you said in your comment. My boots are really shit and cracked so I'm hoping boots are the problem for me. Going to replace them and see if the problem goes away
1978 GS750 I rebuilt the carbs, head and valves machined, installed new rings, electronic ignition, chain and sprockets and new carb boot o-rings. It ran well except at full throttle. The fuel petcock also would not work except on prime. I did vacuum test but the idle did not change. I found some very tiny cracks in the carb boots after smearing them with RTV the issues disappeared. I think the vacuum issue only manifested at full throttle. Just food for thought. Thanks for your video
Great video i did it yesterday as i had my homemade manometer hooked up. Two of the airboots on my 94 ZX6R was leaking. Im replacing all four of them for a crazy price of $65..
@lauriejennifer It still sounds air/fuel related to me. What kind of bike are we working on here anyways? Does it crank up well and pull hard and even? Float set appropriately? Petcock delivers fuel well? Air filter mounted properly?
If you can get it to seal, which may be challenging, then it should hold up to the heat for a decent amount of time, if you are talking about the carb-airbox boots. The carb-engine boots wont hold up very long if they are radiator hose
@Michiganborn1969 Well those numbers sound about right, but they do not test the coil. You can use your multimeter to test the ohm resistance in your coil, check out your owners manual for the specific ohm readings you should experience. It can be difficult to assess for this problem with the bike warm, unless you warm up your bike and then real quick check continuity with the coil hot. What I do tho is just keep a bunch of spare coils on hand to swap out and see if the problem improves.
Ok I understand many people call the pilot screw and the air/fuel screw the same thing. That should start at about 2.5 turns, depending on your manual. Your pilot JET is inside your carbs, and it should be firmly seated, but not excessively so. Finger tight is just fine
Yeah vacuum leaks are when air from the outside are pulled into the carbs or manifold. However some leaks need to be repaired by replacing the boots, and often you do need to pull the carbs to replace them
The low ignition is the point, it means that it can help you detect even a small leak since it is so highly combustible, and even a very small amount will raise the RPMs. And no it no longer damages the upper end like older starting fluid did, because most fluid made today is made with cylinder and upper end lubricant. Carb cleaner is not as combustible so it is not as good at detecting leaks, although it still is somewhat effective
@scrambler250r Unfortunately Im not familiar with many gocart setups. Try seeing if there are adjustment nuts to tighten your cable, or if they cable is very old, it might have stretched and needs to be replaced
Right on always good to meet someone in the area, even if we are moving to Cali in 3 mos. If you ever make it down this way lemme know. Hey you want some competition cams for that kz1000? I got a set Im never gonna do anything with
@vasylivy Besides the fact that your engine wants clean filtered air, if there is a leak the air can come in much faster than normal, thus leaning out the mixture. The air filter retards the air flow down to normal settings, so it is important for all air to travel thru the filter first or else it will run lean.
Any open vacuum lines? Are you sure the boots are tightened all the way? Cracks around the airbox, etc?
Subscribed :) I've only had this bike since last October & my 1st street bike since 1993. I'm still learning where everything is at & how to fix/replace things. I don't want to sound like a dummy, but is the coil located where the other end of the plug wires go under a silver casing mounted on the head tube under the gas tank?
If it
s the silver box then I should also replace the plugs/wires while I'm at it b/c of mismatched plug wires.
great video man, nice and clear. The way you describe your method of approach and what you are thinking is excellent - thanks for posting
Yes vacuume leaks around the boots were the problem, I filled them up with a little gasket maker. Not a very good repair, but good enough. Best to replace the boots.
@rkamphowe Either could be causing your problem. Check for vac leaks, sync the carbs, and make sure your slow jets are not clogged. Good luck!
Yeah a sync might help. Have you checked float heights? Are you getting good fuel flow out the petcock, no clogged fuel filter?
Hey Leonard yeah first thing to check would be vacuum leaks. Also check that your petcock is giving good fuel flow, float heights are set properly, and that your float needles are clean. Watch my video on how to repair a nonrunning motorcycle for more ideas
I watched it twice because it was so helpful
Thank You for the informative video.. I recently got a 1978 hondamatic cb750a and have the same problems..the bike ran great about 1 year ago then it sat in someone's back yard..right noe the bike idles normally, but in order to start it i had plug up what i think was a vaccum hose and have the choke up..going to try your technique asap! Are all vacuum leaks predominately outside, or would i have to take the carbs off? i wouldn't really want to try that on my own kind of new at this whole thing.
thanks saw those but while tempted as they are the same age and millage of my failed ones I reluctantly opted for new. Can only face taking these carbs off one more time this year!
@mrmaxstorey thanks alot for the videos it's very helpful. i have a question for u. how can you tell if a bike is running rich or lean. for me my bike feels like when i go 65 mph plus it feels like it's loses a little bit of power? what do you think.
@bghauck Sounds like you are on the right track. Have you tried syncing the carbs? And might be a simple suggestion, but have you tried just increasing the idle via the idle adjust knob?
@mrmaxstorey I think that's why a surprising number of them are still around, and with such high mileage. Plus, Kawasaki is pretty good at not adding frivolous complications. They don't tend to have electrical problems, etc., as a result. I may be biased, though. ;-)
Id start by cleaning the carbs, replacing the air filter, and setting the float heights appropriately. All of those processes are demonstrated in videos I have put up on my channel
Is the petcock vacuum line disconnected? That might explain both the petcock malfunction and the stumbling at high rpms due to a lean condition
Stock intake, or is the air filter aftermarket too? Everything is all hooked up like the boots and airbox, etc?
Sometimes you gotta clean them a couple times to get it right. Check float heights too, check that your plugs are not fouled and your idle screw is set right
Thanks for posting. I have KZ 440 that is having that exact same problem. Once it's warmed up it runs ok. But starting it I have that same problem to a tee. I thought it was a issue with the jets. What did you use to seal it up?
Great video. I am having a similar problem with the same bike. I bought new boots, and I'd like to replace the screws that hold them in (heads are all pretty destroyed) Is there a certain material screw necessary, as I tried using some spares that were lying around and they wouldn't quite tighten down the whole way? They are the same length and thread (6mm I believe) I am going to use this test today, could use your help though in the fix! Can I seal the boot to the engine intake with RTV?
Yeah it looks like the left one is too fouled to spark properly, I'd recheck that float height and also recheck the jetting on that one, its running rich for some reason. Valves are a great idea to check, you can get a compression tester form ebay for $15, won't be the best but it can get you in the ballpark
Try tying a knot in a piece of tubing and then cutting it off, to make a plug. Or route them together using the same hose
@edempsey3 Typically if you modify your bike with pod filters, you will want to increase your stock main jets by 2.5. So if you are running 100 mains, throw in a set of 102.5 and see if that gets you closer to where you need to be. Good luck on your project, and thanks for watching!
@mrmaxstorey
Its funny you mentioned checking the charging system b/c I just bought my 1st multimeter yesterday to see if there was any issues. With key off the battery was putting out about 12.8V, key on about 12.3V, running @ idle about 13V & reved @ 3500 it hovered about 14V. But this test was all done within 3 minutes. I will try again after a d mile ride & see what reading I get then. The light do dim when I use ether brake or turn signals. Thanks for the reply..... Joe
What will you use to seal the cracks? Great video BTW. Thx.
Hey Max, I remember you saying in another video that you used your vacuum pump (the one for bleeding brakes) to also diagnose carburetor vacuum leaks. Could you possibly explain briefly how you do that? Because I just got my hands on a shiny new Mityvac to bleed brakes and would like to get the most out of the tool. Thanks man, keep up the good work!
@mrmaxstorey KLX 250 (actually, a 350 now). Not sure how to check float. Had a pinched fuel line before from the reserve tap, so it would die when switched to reserve. I already replaced and double-checked that fuel line and it is flowing properly. Not sure how to check either float or petcock. I use opaque fuel hose. How do you see if it's running without spraying gas everywhere? lol
Could be a number of different things. Vacuum leak like in the video, maybe a partially clogged carb jet, or the idle is just turned down too low on your idle knob.
You can get rubber pipe couplings in the plumbing section at Home Depot for $5. From the looks of it, you could cut one coupling in half and use it for both carbs. You can catch them on sale and buy a few different sizes. They come in handy.
is it resistant to gasoline?
Thank you! I’ve typed in so many things to try and figure out why my 82 kz650 was revving out of control!
Is there a fuse for for pump? How about a relay that turns it on? Both of these things fail
Hey i have an old bike not sure what type, but its about 1980's. I have had it sitting for 6 months now and after i got it out a few days ago i have been struggling to get it started. It is just a little 70cc scrambler, but it was a lot of fun and just wondering if you could help. I cleaned the carb, but still just doesn't fire. Any idea's?
Thanks and great video!
Thank you, I didn't even think about having it idle high choked. I have brand new intake boots, was still leaking around carbs and boot
Just found your video and I think I might have a similar problem, so maybe you can confirm. Kawasaki Vulcan 800A with 2 cylinders, sometimes (1-2 times a month) after you start it with choke and the engine gets a little hot, it dies and fuel starts leaking from the carb. You can only start it after that by acceleration at 3-4000 rpm. If you run it afterwards, fuel won't leak, only when you stop and try to keep it in idle state (it will die if not accelerated). Thank you for your time and video, I'll check the vacuum system. Have to mention that the carb it's serviced and clean.
Its time to clean those carbs again, and this time put in an inline fuel filter between the petcock and the carbs. You may have a little grit in your tank which keeps getting into the carbs, causing one float to stick open or one of the float needles not to seat properly. Any time your carbs overflow its not a vacuum leak problem, its a carb problem. I have a couple videos up on how to clean the affected part, and how to set float heights. Good luck
@@mrmaxstorey So inline fuel filter. Also forgot to mention that after it leaks and I run it for 20-30 km at high rpm 3500-4500 then it comes back to normal, no more leaking. Those Kawasaki model carbs have some rubber on the carbs needle which makes them close pretty good.
Yeah most carburetors have that rubber tip, but if you have a tiny piece of sediment it could be as small as a grain of sand, it will cause the carb to overflow. The vibration of the motor from you running it at speed will temporarily dislodge it, but it finds its way back over time and overflows again. Clean the carbs, set the float height, and put in a filter. Done
No, I installed a new petcock kit as well. As soon as I siliconed the boots and the air box boots the running lean and the petcock issues disappeared. I suspect that the vacuum leak was only an issue when the carbs were sucking at full capacity. Anyway I am now confident enough that boots were an issue to spend the $150 on new ones.
I wish you lived in the Cleveland, OH area. I just learned some awesome techniques to diagnosing issues. Thank you for the vid!!!!
Well a lot of motorcycle shops will sell air filter foam by the foot, you can buy some and make your own, although they often are only a temporary fix. To do that bike right you should really find an air filter that fits it properly
hey Max long time to hear im back in Germany after long time on the road and no internet and no driving in Cali :) i now got a Yamaha VX 750 and its my first twin V :) I hope your doing good bro!! and i got a question cause if anyone knows you probly do, what the best way to plug the card sync holes(ont the carb boots) cause theres a couple caps missing and whatever i put on em shoots right off and those caps are expensive so u got a cheap fix?!!! Did u ever come out with that Iphone app?
Thanks. Since motorcycle shops here in Northern California charge $90/hr I can't afford to take it in & I need to try to get this machine running as smooth as possible b/c I just have a permit to ride for now. But when it come time to take my safety & skills test I don't want the bikes performance to be a reason why I flunked the test for my endorsement.
Great video. Was wondering what "redneck repair" method you used? I've ordered some new carb holders and was wanting to ride in the mean time. I tried super glue, and it seemed to work with one of the carb holders....
I just fill the cracks with RTV and then run the bike so the vacuum sucks the wet sealant into the cracks. However no I dont seal up where it meets with the carbs, the clamps should be able to do that
@Michiganborn1969 It couldn't hurt to test it out, perform the test twice once with the bike just started, and once while warmed up. Also consider looking to your electrical system, especially coils. Old coils can develop hairline cracks which are not so much of a problem cold, but they expand when the bike warms up, and the spark cannot arc the fracture, grounding out. Check out my other videos for more diagnostic ideas.
Intake boot vac leaks are a good thing to check first, as it is an easy test. However, clogged pilot air circuit will produce similar symptoms as far as a no idle condition goes. If your bike checks out ok on the vac. test, but only runs with choke on, check the pilot circuit.
Just my experience, but has happened more than once.
Right on make sure that that all your boots are tightened up and that they are not cracked. Also make sure that no vacuum lines are disconnected, and that the air box and filter are installed correctly
thanks for teaching me a new method. Do the boots heat up and get softer and more air sealed?
@TheDriftjockey I only use starter fluid or propane. Some guys use wd40 but I dont think it gives as good results because it is not as combustible. Other guys shoot water and wait for the bike to run worse, kind of the same idea but a different take on it. I don't do this because bikes with vac leaks run pretty poorly as is, so it can be harder to tell the difference.
This is the best info to know. Thanks for the trick with the starting fluid
@Philip Brown your floats are stuck. Tap the bowl with a screw driver and if that doesn't work clean the carb
@mrmaxstorey I should have explained better. It pulls in, it just doesn't disengage & then the cable won't pull back. Have you ever had the cover over the clutch mechanism off? It's so pose to push in disengage it right? Just trying to understand how it work so I know I've got it right. Thanks.
Does it fire at all, even to sputter?
@mrmaxstorey Well, it wasn't the vacuum leak. Just checked. And I even tried opening the gas cap, as a shot in the dark. No change. Idle still wanders. Races, then doesn't, then does again, etc. Eventually, if i leave it idling, it will bog lower and lower until it dies. This happens sooner once the engine is warmed up. Almost as soon as I pull the clutch in to coast, it will bog and die. Frustrating. Praying it's not electrical...
Not bad of a price, hell of a lot better than you would have done at the dealership
hi max i did these checks today and found a crack in the air box and i welded it and i rechecked my air filter which was ok, the bike has improved altho it still does a little rev after i give it a rev ... i have bench sync the carbs with a needle.. would it run better if i got them syncernised properly? also it would run idlol for a good while then just die, it would start back up again with no delay thanks for your help philip
No, vacuum leaks only occur around the intake. If you have a leaking head gasket that is something else, causing low compression. However oil leaks around the magneto or the valve cover won't cause vacuum leaks
I am sorry but you are mistaken. Vacuum leaks at any part of the intake can cause running difficulties, especially in bikes with smaller cylinder displacement and bikes which are particularly high revving. If you take the air filter out of a motorcycle it will run very lean, the air flow will be disrupted with vortexes and eddies that reduce combustion efficiency, the bike will run hot and all kinds of stuff will get in the engine. Some bikes can still run without, but definitely not as well
ok so i have an 88 kdx200. erratic idle and revs pretty high. could the vacuum leak be in the engine itself? noticed a little oil on the cylinder base and a wee bit around the magneto. i cleaned carbs, replacing petcock, lowering air pilot to a 45, adjusted throttle cable...not sure what else it is, so replacing these gaskets could be the answer-yes??...good vids
@OldFordsRun Squirt some pb blaster or wd40 around the carb boots, then heat them up with a hair dryer. The rubber should get more pliable as the lubricant expands, freeing them
Thanks, I was able to tighten the intake manifolds and it appears to have solved that problem but now the bike will start and idle better however dies with any throttle. I turned the key on a few times with my ear and hand on the fuel pump and it doesn't seem to come on at all so i removed the fuel pump and put a jumper on it and it kicks on but I don't think it works on the bike. I have to charge my battery and see if it's not putting out enough to run the fuel pump. I'm lost lol
Commonly, guys will replace those old screws with allen heads for ease of access, Im not sur eif there is enough room to get a socket on a hex head down in there. As for the correct sealant, I typically dont use any if the rubber is good, but I always check for vacuum leaks after installation. Some guys use rtv or other stuff, it depends on your preference. You arent going to hurt anything by using rtv, just let it set before running the bike because heat, vacuum, and gasoline will corrode it
very nice info :)
what are the alternatives you can spray?
Sorry I have no idea. Might need to try a couple jets and experiment before you know which is best