We Blew Up Our Hovercraft...
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Make sure the rod didn’t punch a hold In the bottom of the case causing the lean condition. The clearance is pretty tight sometimes and that can happen. You’ll rebuild it and it will blow up again. It’s either a carb issue (pop off?) or an air leak
Check your base/crank/intake tract gaskets for leaks, sucking in air in these spots will make a lean cylinder. 32.1 is fine for that engine and make sure you're pilot jets are kept clean as they will clog up easily and also lean said cylinder out.👍
Seriously Ike CALL MY MOM!
if you find oil in the muffler then it is not burning it, Every engine burns different due to carb settings and sea level, Back it off until it runs faster then add more oil to the mix, example lawnboys loved 4 Oz per gallon but echo or stihl wanted 50;1 so the exhaust tells you if it is happy
I have a whole bunch of 377 or 380 skidoo motor parts if you need any
Regarding fuel mix ratio: Ask the ultralight flyers. Their life literally depends on the motor running, and a lot of them use Rotax engines.
Yeah but the engines they use are built different to a snowmobile engine so their advice might be wrong for the application.
@@dylanzrim3635 Maybe some... I see a ton of only slightly modified sled engines. Yamaha Apex is a popular option.
The Rotax 470/503 is a very popular ultralight/Gyro engine.
40 to 1 is a richer mixture in terms of oil. it is 40 parts gas to1 part oil. 50 to 1 is 50 parts gas to 1 part oil. The harder working a 2 stroke engine is, the richer the oil mix needed for lubrication. Many old snowmobile engines actually ran 32 to 1 or richer, some in the 70's even as rich as 16 to 1.
As you mentioned while disassembling the engine, fuel mixture may not be a problem. It’s the individual cylinder that somehow went lean and got extra hot. It could be a fuel delivery problem but it could also be an air delivery problem. 2-stroke engines draw the fuel-air mixture into the crankcase and use the downward motion of that piston to push the mixture unto the cylinder. It could be that delivery is okay but extra air is being sucked in through the crankshaft seal. Definitely check all the seals and it’s probably cheap insurance against melting down another $200 worth of parts.
last boat was a 26 all ceder cabin cruiser. don't even remember what model was .
still got one of the port holes. and a couple of hing'es.gave a lot away to my kid's.
they wanted to remember it.
50:1 or 40:1 good. Older engine best with mix verses trusting an injection system. You can pull the plugs and see whats best... Your meltdown was likely the crank seal on the side thats bad. Remember to pop in a new seal. Also remember to get the base gasket sealed good. Head is fine. Clean it. You can smooth it out tapping with a ballpean hammer. I wouldn't mess with jetting however use a kestrel or similar wind flow meter to get the air flow the same between carbs both at idle and when revved up.. Should have identical flow. I have blown several sled engines over the years.. Usually one i just aquired and were sitting. Crank seals are number one culprit of a melt down.
If a 2 stroke ain't smoking, it ain't got enuff oil in it. The right amount will help with compression.
My hydro, I use a,qt per 5 gal oil/gas. I'ld see if it's buildable, then modify ports, carb and timing.
By rules we have to run pump gas. Our two cylinder 7.5 hp 15 cubic inch rotary valve engine. It twist 9200 rpm, pushing a 11' 9" pickle fork hydro 72 and change mph
Read your spark plugs, they tell the story. Chocolate brown is what you are looking for. Chalky, your frying it black to rick
48/1 only use ITASCA® Outdoors 2-Cycle Engine Oil. you changed the exhaust , change the jets. learn to listen to your engine. you are running full throttle more than a sled would, jet super fat till you figure it out
How do you judge your fuel mixture is Buyer reading your spark plugs on each cylinder
Only advice I'd give on this (and other 2-stroke engines), get the repair/service manuals for them, and study them, especially if they have a factory separate oil injection system, and listen to what the manufacturer says, too many "internet experts" out there who get things wrong all the time, but will be utterly adament that they are correct, and end up causing people to damage their engines from listening to their bad advice...
You needed to richen up the fuel mix on the carburetor can you guys put the motor in you bypass the injector system for the oil to make it fit so you use premix that's fine but you got to consider now that you're mixing oil with fuel you're taking away the volume of fuel in replacing a portion of it with oil henceforth you're getting less fuel and possibly causing detonation also on high RPM Marine jet ski and boat engines prefer higher octane fuel because they are a lot harder working and higher RPM imagine driving your car to work in first gear for 30 minutes that's how a boat engine runs also the Piston closer to the drive shaft fan jet pump aka the PTO piston always works harder and will be the first piston to fail typically
Too rich a mixture can also seize your engine. All that extra oil gets really hot and burns up the piston and rings. Been there, done that. Also, you removed the oil injection system!
Why you running an outer cover on one air filter and not the other? Jetting should stay the same on both carbs
My old snowmobile I used to run 32/1
+= 10 shouldn't hurt, amount of smoke is the key. look at a running right snowmobile?
Rear cylinder alredy running hotter by default, the socket is only in the front filter so the rear one is getting also more air and going even leaner.....
This sure was a jet/carburation issue at WOT.
What is the car on the Hoyts? Please
Hoist sorry
You have your oil ratios wrong 50:1 has less oil than 40:1
I aways forget about how cool hovercrafts are...
Snowvercraft!
They're handy when you've got to go PLACES YOU CAN'T EVEN WALK.
.. Y'know?
Y’all should build one….
Ex Watercraft 2-stroke tech here. 40:1 or 50:1 is fine with high quality oil. The problem is, you changed the exhaust and intake and ran it at a higher RPM for longer then designed. It leaned it out badly. An exhaust temp gauge (I ran one on all my 2-strokes when desert racing) will let you know if you are hitting piston melting temps. But next to that, go at least 3-5 sizes bigger on one carb, then see how it runs. When you get to the point that it blubbers because it's too rich, then go down one size. When you feel like it's close, then do the same for the other carb. You want both as rich as you can, taking note that the leaner you get, the better they run until they melt the piston. So it's a balance of getting acceptable performance with being as rich as you can get it. Also pull out and read the plugs. This jet, test drive, check plugs, change jet, test again, normally would take me about a half day on a 2-stroke with no baseline. Like if someone changed motors or carbs. Take your time and get it dialed in. Since you are mostly running that thing at WOT, you should be able to get away with only testing at WOT and changing just the main jet, then when that is good, adjust the air/idle screw to get it to idle, and/or move the needle.
Quick edit for certification. 2-strokes, and doubly so air-cooled depend on un-burned fuel for cooling. Too hot of combustion temps will cause the piston to expand, and scratch up the cylinder walls. You will normally notice 4 total scratches on the cylinder walls that line up with the piston pin areas as that is the thicker part of the piston and it expands more.
If you take running lean too far, normally with a multi cylinder engine with multiple carbs, you will get pre-detonation, normally indicated by a hole in the top of the piston or destruction of the top of the piston. This is really common when one carb gets too little fuel, but the other keep going, so the engine is run past when you should have shut it down.
Oil starvation from incorrect pre-mix, I almost have never seen. When I do the piston has scratched up the entire cylinder equally, and you don't get just the 4 big scratches, but it can be hard to tell exactly. Melted/bad rod or crank bearings are a good indicator of lack of oil.
As for pre-mix ratio, I have seen older 2-strokes require 20:1, and high performance ones require 50:1. We have better oils then we had 40 years ago, so ratios have changed. A really rich 20:1 will cause oil to build up in the exhaust, lots of smoking, and build up on the plug. If it's not a new engine that specifies 50:1, OR it is an turned race motor, I normally run good old 32:1 with Yamalube R1 or other good off-road oil.
I still maintain that in this case of the the failure in this video, the engine's jetting was not correct for the conditions the engine was run under. The water in the fuel may have also been a factor, but the engine needs to be properly jetted to handle the different load it's under, along with the changes to the intake and exhaust.
This guy knows his onions
Great advice! I've been a professional small engine guy for forty one years too. My approach for adjusting the main jet is to start out rich and lean out as previously suggested but do it at no load. Remove the belt (is it belt driven?) and it should "Four cycle" with out a load and smooth out/ "two cycle" under a load. You should be (about) two sizes richer when it just starts to "two cycle" under a load.
Backyard guy here, I thought for sure leaned it out a lot by cutting the end of the muffler off and emptying the packing out. Bigger jets!
What do you think about the metal shavings that fell in the pipe when they Sawzalled of off being sucked into the motor on the negative pulse?
You forget aircooled 2 strokes run hotter then their watercooled counterparts in watercraft. So yes 32-40 to 1 would be fine for this engine, this is also the ratio that many ultralight airplane pilots use.
A good quality oil for aircooled 2 strokes is a must! I use Power Punch 2 cycle oil when I can get it. Our local supplier is hit and miss.
when you remove restriction from the exhaust of a 2 stroke, it causes a lean condition. you need to rejet the carbs to run fatter to make up for it. i do it with chainsaw all the time
❤
Fuel/oil mix don't matter if the carbs aren't jetted rich enough. I always prefer to see a little blue smoke out of a 2 stroke.
Bingo
yea . with that being an old air-cooled snowmobile engine(used in the "summertime" It should have been some blue smoke coming from that engine...
And if you're ADDING oil, you need to up the jetting at the same time or you're leaning it out further.
Well they should have left the oil injection pump system on. Smh never understood why anyone would remove that. And try to run pre mix. It’s not made for that.
Hey John I recommend you might as well replace the crank seals and stuff to make sure there's no leaks and then do a leak down test on a crankcase especially since you had an overheating problem you could have burned out seals and not even know it
I was going to say the same thing. A leak-down test is a must after a rebuild.
th-cam.com/video/tOZL01I5g1s/w-d-xo.html
my mentality with two strokes was always that there needs to be at the very least a bit of blue smoke coming out of the exaust
When in doubt, enough oil to smoke out mosquitoes is enough oil to keep it lubricated.
My experience with 2 stroke snowmobile engines and dirtbike engines is to air on the Rich side always worked for me anyway
I'm with ya on that one,,I've always mixed mine a little heavy,,if I didn't see a little bit of smoke,,I'd put more
I mix all my 2 stroke engines 4 OZ to a gallon of gas. that's around 32 to 1. I have found out that diaphragm carbs last longer stay more pliable and extra oil doesn't hurt anything. More lubrication keeps parts from wearing so bad. Also spark plug is much cheaper than piston and jug. That's just what I have found that works for me anyway. Thanks for bringing me along.
That cone on the fan outlet is known as stator vanes, in this situation it's used to convert outlet swirl into additional thrust, also making the air exit more laminar way, also contributing to thrust you can think of it as additional counter rotating fan from perspective of airflow.
Also you should maybe replace the crank seals because if they go bad they can draw in air and cause a lean situation
Truly nothing warms my heart more then a group of good ole boys working on a project!!!
Hovercraft series and the king midget series had me stopping everything and watching wherever I'm at....here for it!
you uncorked the exhaust by cutting the tube off and making it go straight out, that made the fuel mix WAY off! when you pulled the plugs, i could see they were completely grey, so it was running WAY LEAN!!! it needs to go up in jet size to make the plugs the correct cardboard brown they should be.
Also running a more oil rich mix actually makes the mix "fuel lean" because you are replacing the fuel with oil.
That shouldn’t do anything to it it’s carbureted and doesn’t have an oxygen sensor telling it how you feel and air make sure it has so it’s gonna stay consistent there And if you look that was more like a silencer because it still was straight through like a straight muffler, so realistically, they didn’t cause any pressure change, and if it was, it was very minor most likely that motor had some issues prior to them getting it
At 24:25 that wasn't the only thing uncorked!
💨💨💨🤭@@mattconboy8490
Pretty sure you overheated the engine on the first episode. Do a replay and see how many leaves where plugging the cooling fan intake.
New engine had a cooling fan on it. That large round opening on the front of it I believe
@@jordananderson8299
@@jordananderson8299 In the first episode that cooling fan mesh was plugged up on the front of the engine. As well as the main power fan.
@@Taterchip871Yeah, I was cringing when I saw the leaves plugging the cooling fan intake and they switched drivers and kept going.
I agree with the leaves... Snowmobile engines aren't meant to run in warm temps also, they are dogs above 35 degrees, I grew up with snowmobiles, and live in the northeast... I know it might be costly, but you should get a liquid cooled engine and don't bother with a fan cooled engine.
One thing to remember is these older air cooled snow engines are default jetted and designed to be operating in the 0F-20F ambient temp range which keeps them much cooler. Running in warmer weather means less dense air and less cooling - running 40:1 is usually a good choice, with one jet size up on the carb - if your two stroke isn't smoking a little you're too lean. Dual carbs are always a danger running pre-mix, any clogging in a jet or in the float needle means you run that cylinder dry which kills it in no time - if you sense a misfire, stop it immediately!
“Ya I almost burnt the shop down …three times today” 😮 😂
Use mueradic acid on a rag to remove aluminum from jug but only inside sleeve
31:47. I hope him saying maybe it got a valve is a joke....... He does know it's a 2 stroke right? LMAO
You can run these engines on pre mix if you mod it correctly (Jets, block off plate, etc.) I'd highly recommend going back to the injection pump.
Putting in more oil doesn't hurt performance, just jet accordingly. I like to be around 25:1 on my super rare engine for which there are no parts available at all, 30:1 on others.
A bit less oil would probably be fine but why risk it. It's a 2stroke and it needs to smoke. I know good oil isn't cheap nowadays but it's not like you're gonna go through 10 gallons of it in a hovercraft.
The tough part about a hovercraft is you really can't slow down to turn or change direction, you need to be going all out and plan every move out ahead so you can slide into and around everything. I bet it gets better with more practice.
OR... And hear me out... Add a second motor purely for lift. Then you can always have the float, and you totally can decelerate to make turns and get through obstacles.
I think you should try it.
Some are set up this way
It looks like it handles like a jet ski. You really only get turn when your in higher rpm
Sounds like a cool challenge. Some creative fabrication, and it would make a cool couple episodes in the Hovercraft saga.
"maybe it's hittin' a valve" baaaahahaha goooood one dude
and out of blinker fluid
Some things to watch out for with 2 strokes and oil/gas mix.
- if it's premix, know the mix OR default to 32:1. Then take a plug read to know if you're too lean.
-When going from oil injection to premix, you'll want to go up 1/2-1 jet size on the main to account for the differences in molecule size going through the jet orifice. Oil molecules take up the space once occupied by only gas.
Great stuff guys! Love where the channel has gone. Keep it up!
oil rich and check plugs, plugs don't lie
You literally have no idea how many times I have tried to educate people on that! I have also seen them just leave open air leaks where injection lines hook up to carbs and or crankcases!
Great explanation.
I was always told to use high octane fuel and just mix your own. We use small 2 strokes in our 1/5 scale rc's
@@fishininjun I use 32:1 with 110 octane and klotz premix in my baja 1/5th scale.35cc Taylor engine.
IMO a little extra oil doesn't hurt anything. Might make it smoke a little more and not make peak power, but it generally doesn't cause damage. Id run 32:1
Might also consider running the stock oil injection pump. At least with that both the cylinders get oil no mater what happens with the carbs.
Adding more oil can actually make it run lean on the air to fuel ratio. Because you're diluting the fuel down with oil.
@@bb-ballistics1706 I could see that happening with large amounts of oil in the gas. But you're only talking a few ounces per gallon. Even if it did slightly lean the engine with the extra oil it likely wouldn't sieze/burn up.
When you add more oil you make the engine more lean! I tried tellin yall last time when you arent using oil injection you need to jet up!! You should use the oiler for better crank lubrication especially needed at extended high rpm. If not JET IT UP!!!
the 289 dude's video was about getting gas that had diesel mix in it from the station right by him.
Thnx.Wondered by the title what went wrong.
he's still not real sure. but seemed to be bad gas.@@bryduhbikeguy
@thunderhead289
thank you for helping and old guy out sir.
he's a good show to watch.@@IGrocker
On the bright side your lawn is now de-thatched and cleaned.
The safest course of action is always to mix at an oil-rich mixture (i use 25:1) and then adjust carb settings for that. Then if a lesser oil mixture is used, there will only ever be more fuel, which is not going to hurt anything. Always start too rich on fuel.
I’m no 2 stroke expert but small engine 2 stroke “weed eater,chain saw” should be 50 to 1. However larger 2 strokes need a little more. I run 32 to 1 in my banshee and the carbs should be jetted according to the temperature and climate.
I think when you cutt the exhaust you have taken out the catalytic and then its needs more fuel because better flow
That to could be one of the problems and plu they have a cooling fan on there for air flow around the heads if they don't have plating to direct the airflow to that back cylinder that will get hotter than the front cylinder
These are the kind of vids , i luv from you guys , complete random chaos.
I have Craftsman saw that has a Poulan exact model counterpart, one says 32-1 and the other 50-1, always used 32-1 bc you'll fair better with more oil -- always,always,always verify crankcase seals for pressure and vacuum.
Stick to 32:1 and jet accordingly. Every time you change fuel/oil ratios, you alter the viscosity of the fuel and it changes how much fuel the engine is getting. Lock the fuel/oil ratio in, and chop some plugs! 😁
Check crank seal too
If you un-restrict the pipe, its going to run lean and overheat. Your mixture ratio is not nearly critical as your jetting.
nah, he messed with the pipe, but he didnt mess with the expansion at all, that hardly effects anything...and it would have effect on both cilinders, they just have a leakin crankseal, on the side whats damaged...
@@wimvandesteeg1353 In the video, he sawed off the silencer. That lost backpressure, so the carbs went lean. They needed richened to compensate for the extra air. The rear is always hotter, it went first.
Check you crank seals. If they leak it will lean the out the engine. My experience has been that the PTO side wears quicker. Especially if your bearings are wearing out.
50 parts gas to 1 part oil doesn't seem oily enough to me. I'd go 20 parts gas to 1 part oil. Get a lot of oil in those cylinders. You may foul out some plugs. But, that's no biggie. If that happens, try 32 parts gas to 1 part oil. Err on the side of caution. Spark plugs are a lot cheaper than pistons, heads, and jugs.
You also need to put a baffle on the end of that exhaust to give a little bit of back pressure and stop the motor from over revving.
Ask Rotax. These engines are used on ultralight aircraft so they must be pretty reliable. It seems the manufacturer would be the best source for info.
Classic Two stroke Tuning problems, main jet is too lean, so you keep adding oil to compensate, but without enough fuel to keep it cool, it could be 50% oil and it will weld the piston to the cyl-
Seizing Two stroke almost never means add oil, it means MAKE THE MAIN JET BIGGER-
if it's a Multi-Cylinder Two stroke, the seals between Cyl 1 and Cyl2 are bad and the piston with the slightly more compression runs rich and the other one runs lean, Sitting for any length of time makes the seals dry up and go bad - Rebuilding Multi Cylinder Two stroke cranks is EXPENSIVE and has to be sent out (Ya'all cant build one)
You ALSO cut the pipe off and opened up the backpressure which will change everything and never re-jetted
CHECK YOUR CRANK END SEALS OR THE ONE BETWEEN THE CYLS- it will trade intake charges between or suck in outside air and melt everything
29:07 This is a severe duty application. 50:1 would be oil starving in a light duty application like the snowmobile it came out of.
Given that this engine is operating under constant, heavy load at all times, I would give it no thinner than 25:1, and preferably 15:1. It's gonna smoke like it's coal fired; that's how you know it isn't going to blow up again. You may have to adjust the carbs somewhat to get it running nicely on such an oil heavy fuel, but nobody's ever blown a 2-stroke because they ran too much oil through it.
they could probably add more pitch to the blades to get the rpms lower.
@@skmetal7 It isn't the RPMs. The issue is that the engine is under a constant, heavy load. It's having to work hard the ENTIRE time it's in operation. This engine is not designed for such a task. It is designed for a fairly light load where it's only having to deliver max output on occasion and is otherwise at partial power.
When you're riding a snowmobile you're generally not bogging the engine down making it pull as hard as it can the whole time, even if you're WOT blasting a flat area.
Further exacerbating this is temperature. When you work an engine super hard, you're gonna get it hot. Snowmobile engines aren't all that good at cooling themselves off because they're designed to operate in extremely low ambient temperatures. Even in a fairly light duty situation...IE someone's shoved one in a Yerf Dog...they're going to be highly prone to overheating. When they're being asked to pull most, if not all, of their rated power continuously like in this hovercraft they're not gonna be able to cope. We see this play out in the failure; the cylinder that died was furthest from the fan and it had evidence of running MUCH hotter than the other jug did.
This engine needs a LOT of oil run through it if it's going to survive on a hovercraft. The engine they took off was designed for this purpose and they could have that thing WFO from now till doomsday it won't care. But this engine WILL care.
Might not be a bad idea for the guys to rework the cooling on it, too, and instead of relying on that dinky little fan the engine has use the big-ass fan it's turning to pull more cooling air through it.
The squish band is very important on 2 strokes. You can't "clean up" that kind of damage without altering the squish band too much. If you have pits in the squish area you can get detonation and will certainly adversely affect flow in the head. If the clearance is too much, you will loose a lot of power.
Was you guys using the right 2 stroke oil? Their is a marine version that is specifically used for water cooled engines and a air cooled version that is specifically designed for the higher temps that air-cooled 2 strokes generate.
u guys cant use 87-89 octane on pump gas but if you have to use pump gas then you need a 91-93 octane minimum but you can buy pre-mixed fuel from tractor supply in the weed eater section they even have VP RACING FUELS there and with a 95+ octane rating
This is typical for a 2 cilinder, the crankseal on that side is leakin, maybe a worn out bearing? the belt pulls pretty hard on that side...makes it run lean on that cilinder...if possible, get some Viton seals, the purple ones, those are more heat resistant....this is not a carb or mix problem, the other cilinder/piston looks undamaged...40 to 1 should do fine, i use 35 to 1 on my 2 stroke racer, but thats a 15k rpm machine...just use full synthetic 2 stroke oil..you could jet up a bit, just to be safe, can always go back
Agreed, I run 40:1 in everything. My snowmobile swapped golf cart has a rear crank seal on clutch side weeping oil but it runs fine. I will eventually get into it, replace the seal and also change the front seal out for good measure
50 :1?!! My god nothing two smoke (especially a rotax) truly should use a ratio that thin. You guys need 25:1 or around there for something running essentially WOT most the time. Why in gods name 🤦 😂
You guys need to take this to a beach that is where a hovercraft truly shines!
lol have you seen heavy d sparks video where they wrecked a hovercraft on a beach? lol
They still suck
Perfect for Busco Beach!
Yeah at 1:35 it looks like straight gas not premix. Maybe 100 to 1... I'm thinking that motor was made to run in 20 degree weather and the thin warm summer (spring) air isn't helping to cool it down enough. The jetting is probably lean as well. Basically everything is working against it. I'm thinking it ate a ring by the end.
NO OIL IN THE CRANK CASE. Rotax motors need to have a oil tank to cycle oil through the crank case even if the the oil pump is unhooked.
According to a few different Ski Doo shop manuals the 503 uses 40:1 during break in and 50:1 after break in. Also, perform a leak down test to rule out a leaking crank seal. This could be the reason for the melted piston on one side.
Fellas, raced two stroke motorcycles from 1973 to 1992.
Always use 32-1 and jet it using plug readings to get to proper fuel air mixture.
Run good 2 stroke oil
Pressure test crankcase to ensure no leaks. Use new gaskets.
32/1 with crap oil MAYBE. THAT WILL CARBON THE WALLS, BREAK OFF AND SCORE YOUR PISTON. THE OIL NOW IS NOT FROM 1970.. come on. really
It's not the oil mixture! Any water in the fuel throws EVERYTHING off! That was really avoidable!!!!
Gordon Jennings wrote the 2 Stroke Designers Handbook, everything you never wanted to know about building 2 stroke engines to the ninth degree.
Results of oil ratio testing
Suzuki PE 250 single @7000 rpm with varying oil ratios, 15:1=27.3hp, 20:1 = 26.9 hp, 30:1 = 24.5 hp.
More oil cooler running engine, cleaner running engine and more HP
50:1 sucks
Interesting, I didn't think it would be that big of a difference.
Those seem like really rich mixtures. Would the difference in oil technology from 1973 to now explain why we don't see those ratios recommended?
was thinking the same, I used to work at a Suzuki shop in the late 70s to mid 80s and at that time most 2 strokes were at 20 to 1 and maybe 32 to 1 at that time was as lean as you wanted to go.
You should move the fan grill. There should be a say 1 to 2 inch gap between the grill and the fan bellmouth. Otherwise the laminar flow across the bellmouth is broken up and you loose significant fan efficiency at the blade tips, which is where a lot of the horsepower goes to. Mount the grill on 3 or 4 pillars to get the spacing.
"maybe it is hitting a valve" 🤣
What you said at the end of the video is a good plan you need a pretty rich mixture i usually stick with 32:1 but ive had to run 40:1 on a ke100 recently because it was loading up on me too often. You're on the right track with the jetting change its a huge and often over looked part of a two stroke if you run a four stroke lean enough on fuel you can over heat it and cause the same melted piston problem you guys are currently having the way to avoid that with your two stroke is to jet it so fat that it loads up and wont rev then lean it out just lean enough that it revs smoothly again. Thanks guys been watching since 2015 or 2016 and your videos are always fun to watch
I believe that in the first video when you got the Rotax twin you removed the oil injection pump. The engine is designed to run with a certain amount of oil being pumped into cylinders as per the rpm. The higher the rpm the more oil. When you are running a premix, when you are wide open you could be leaned out from 40 or 50 to 1 to as much as 100 to 1. Also it also designed to run in a colder enviroment. To keep the pto side cooler you could run a colder plug on that side. You could also go to a single carb setup which will maybe lose some performance but remove the possibility of a lean carb on one side.
Idk every machine I’ve ever had, had the oil injection disconnected and ran fine on 40:1
doesnt really make sense, yes, the oil injector gives more oil, on higher rpm, but thats just because the amount of gas through the carb is higher too, ideally it would give a solid mix, on every rpm, reading the rest of your comment, well, no offence, but i would never let you do anything on any 2 stroke😅
Dosen't the rotex inject a little oil into the end of the crank?
oil injection on 2 stroke is on a 1 to 1 pumping ratio - i.e gas oil ratio never changes at any rpm - designed/built and wrote 2 stroke engine manuals to include service warranty training for several years
Guess I was misinformed. I hate 2 strokes and won't work on them. Quit working on snowmobiles years ago. Google the question " Does a 2 stroke premix run the same gas/oil ratio at all rpms
Increase the main jet size by one or two and run 32-1 for high rpm 2 strokes that live at that high rpm’s need more oil but usually lean melts the center of the piston that looks more like the ring stuck and broke the piston on the way back down
Ran 50 to 1 in all 2 strokes never had a problem for 62 years. Chain saw, snowblower, snowmobile, jet ski, dirt bike
And remember, the ultimate hovercraft is one that's full of eels.
Good Python reference!
You fried the rings, now me and the mad scientist have to put it back together.
Old sleds are 32-1 and stay away from cheap oil. 50-1 is lean and im guessing its cheap oil too 91 with Amsoil 32-1 is the best
Need to keep the rpms in check too. Blade pitch determines that at wot. Do you have even any idea what rpms you were running? Might be good to find out if not.
check the crank case seal on that end it might be sucking air in and making it lean out on that jug
Running mismatched air filters won't help with fuelling setup .
just ask the manufacture of the engine what oil mix to run. they will know
You can use muriatic acid to remove the piston transfer from the cylinder
Guys rotax 503 is 50:1 I just goggle it 87 octane to 2 stroke oil that you get at Lowe's or home Depot echo 2 stroke oil will work just fine .
2.6 fluid ounces of oil per gallon of gas ⛽ Bryce
These 2 dummies need to stay away from 2-strokes.
CHECK THE CRANK SEALS!!!!!!!
Seems like the 1 carb was starved for fuel or a leaky boot or crank seal
Fellers! Sure, the oil is the lubricant. But the fuel/oil mixture is not only for providing power it also cools the engine! Through several means! Evaporative cooling and the Venturi in the carb.
Run the carbs rich in your warm weather!
I have a lot of two stroke experience with dirt bikes snowmobiles you name it I've played with it including converting snowmobile engines away from oil injection and making them premix if you're running 50 to 1 that engine is going to run so hot and meltdown especially being driven in the summer time your issue has nothing to do with octane nothing was pulled in you did not have enough oil in your fuel running more oil can make it run leaner but it won't do damage like you're seeing here because you would have loads more oil your problem here is running your 50 to 1 I would around somewhere between a 32:1 and a 40 to 1 and keep it there and leave it alone. As far as knowing if your mixture is right I like to see a little bit of smoke on first startup but when it's it is up to temperature and being ridden ,light to almost no smoke if you're still smoking a lot then that means you have too much oil
I would definitely not run anything leaner than 40 to 1 in something like this I would even lean towards 32 to 1 I know everybody says that modern oil this and that but it's better than blowing up an engine unless you're fouling spark plugs constantly run it a little heavier
You do realize that that's a snomobile engine and runs in cold weather, therefor your air cooling system is running around 30 degrees hotter than it normally would be. Weld some longer cooling fins on the side that the fan air passes through... just on that cylinder.
FYI 50:1 has less oil in the fuel than 40:1
I don't think that was your problem but just an FYI
Get the ID numbers off the motor, it is stamped on the clutch side housing-half by the fan, and find the fuel ratio for that motor. Most all two stroke snowmobile motors are 50:1 as long as no up grades to motor or carbs have been done. I have two sleds with the same motor and run 50:1. You'll get it figure out! Good Luck guys!
If she ain’t smokin she’s gonna be broken.
Well that didn't last long 😂😂😂😂 full send 😊
the airfilter with the cover was restrictive enough to keep afr proper on first cylinder, but the other airfilter without cover was freeflowing enough that the afr went lean on cyl2
Another theory could be the lack of fuel mix going into that cylinder. I've seen pistons crack and break apart from friction heat because of the lack of fuel mix in 2 strokes. Mostly weedeaters and chain saws, but they all work the same. Would check the carb ports thoroughly. As for mixture. I've always done 32:1 and 40:1 for break-in after 8 hours of run time. Then 50:1 every run time after that. Unless it sits for months. Then do 40:1 for 3 to 4 hours and back to 50:1.
Yeah running low grade gas can cause issue's up here in Canada we run 91 octane in our snowmachines
well i´ve had many old air cooled 2 stroke bikes and when i knew i was going to go on longer trips on the highway meaning open throttle for extended periods of time wich you guys are doing with your hovercraft then i would put a 25:1 or a 33:1 mix in to play it safe even if the factory recommendation was 50:1...the factory recommendation is usually based on normal driving and not long periods of open throttle driving like a hovercraft, and especially on a hovercraft with an aircooled engine your actually pulling more air away from the engine then you are feeding it new cool air, first because your sitting infront of the engine and blocking airflow from the front, second because your not travelling very fast wich means less fresh airflow, and third because unlike an airplane propellar for example your not pushing fresh air over the engine but pulling it away on a hovercraft, therefore running hotter then for example a motorcycle, snowmobile, plane etc...so i honestly recommend adjusting the mixture to double the recommended dose, so try it with 25:1 (1 gallon oil into 25 gallons of gas)...and get the newest and best 2 stroke synthetic oil you can buy...the lubrication is much better then the cheap stuff or mineral oil...if you should notice that your engine has less power then before or doing what is called fouling (leaving a dark brown slimy residue on the pistons and such) then the mix is to rich and you should slowly reduce the mixture to 33:1, 40:1, and so on until no more fouling is seen...but that been said fouling is still better then a seized engine, and do to the constant full throttle and bad ventilation your hovercrafts engine has to endure concider starting to test with a 25:1 full synthetic mix and 90 or higher octane premium fuel, here in germany i run all my aircooled 2 strokes with 98 octane and full synthetic oil...and since you guys are running a 2 cylinder 2 carb setup your going to need to sync those carbs perfectly...a sync tool is not expensive if you do´nt already have one, but syncing those carbs is crutial especially for aircooled 2 strokes that are operating mostly full throttle...
that been said thow as i wrote in an earlier comment, maybe concider doing an EV conversion...a EV conversion kit will probably cost you less or the same then what your paying to repair that old 2 stroke that might need more then a new piston and head after getting as hot as it did + you´ll get more instant torque and higher rpm going full EV, and maybe even save some weight with a light battery pack + no more pain in the a** with pistons getting stuck or wrong oil or fuel mix etc...something to think about...i know your petrol heads like me but i´d risk it and try something new + maybe some new EV fans will suscribe!
or use a high reving 4 stroke maybe even watercooled... somewhere between 7 ,000 to 10.000 rpm should be more then enough to get lift on that hovercraft if the fan blades are adjusted right...horsepower is´nt that importent since your only resistence is air...torque and rpm is whats going to do it for this hovercraft and why going EV just might be the best solution!