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Discussion Starter · #1 ·
So I'm not sure if this has anything to do with my failure, but figured I'd run it by you guys to see what you think. I may be off base saying the bearing buddy failed, but what appears to have happened is the cap that plugs my fill hose came off and the hose puked some isoflex, and appears to have provided air thru the PTO side and leaned out the mixture.

This all occurred last weekend when the weather went from super cold in MI to mid 30's and a decent amount of snow on the ground (adequate cooling to the exchangers) all became very heavy. I was worried about cooking belts because you could feel the sled had to work a lot harder to turn the track. I'd compare it to riding the wheels off a 125 2 stroke at Baja MX (for you Michigan guys) it just felt like something was bound to fail. I was on the pipe (spinning about 8k) breaking trail in about 18" of the wet stuff, when the sled felt like it was running out of gas or a top end was cooking so I let the sled coast to a stop and killed the engine. I've blown up my fair share of 2 strokes to know better than to fight it and keep giving throttle or try to re-start it. Coolant temp was running 4 bars on the cluster consistently all day, never went retard mode or got hot. The motor spins freely, and feels like it has compression when pulling it over. Passed the trailside compression test (finger over plug hole), but just loaded it into the truck and got it home.

Put my gauge and tested compression cold the next day when I got home, and made about 130psi PTO side and 135 PSI MAG side. They're usually dead nuts 150 psi each (on the same gauge).

Do you think the bearing buddy had anything to do with it? Could the fill hose act like a snorkel and pull air into the cases or is there an inner crank seal that would prevent this? There is a yellow "haze" inside the y-pipe that possibly coule be from buring off isoflex? Both plugs came out too white for comfort, but the PTO side was nearly pure white, while the MAG side had some tan color and

I have not got into the bottom end, but replaced the top end about 1500 miles ago. Sled has a RK tek/Wossner pistons, head re shape, ECU reflash, v force reeds, and dyno port y-pipe, single pipe, and can. The top end did eat a set of reeds (1 petal each through both cylinders) about 750 miles ago. This left some minor imperfections on the skirts, but the cylinder walls and rings still looked beautiful from what the bore scope could show. Compression remained 150 psi in each before and after the reed failure.

Still in the process of tearing it apart, have yet to inspect the reeds or see what the pistons reveal when I get the cylinder off. Posting a few pics of what I described thus far...
 

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Nice catch on the yellow Isoflex burn in the y-pipe.

Plugs look nearly new/white. The heat range also affects plug color, but white ceramic remains white. EGTs are the better bet to ensure both sides are even.

As for bearing buddy cap leak causing a failure, I really don't know without any exhaust readings to confirm. There is still an integrated seal on the inner pto bearing. It seems the the Isoflex seeped through the integrated seal, so obviously air will seep by as well. But how much of a leak is necessary to cause a lean failure? Too much guessing imo, which is why I go back to the EGTs. Say for example we added a intake port on the pto side of the crankcase that we could control with a ball valve. Then we could open open the valve and watch the effect on the pto side EGT. I'm not saying to do this, just an example to show we tend to speculate with no exhaust reading.

In any case, a leak test is needed for the crankshaft, crankcase, and a whole bunch of other things. I spend a large amount of time in pre-teardown tests. I leak test all engine seals/gaskets and mark each bolt position prior to removal. In some cases I use a torque wrench to remove each bolt, and other times I recheck bolt torque on a percentage of bolts, especially the head and cylinder. I am not worried about a few Nm, but rather something that doesn't add up. The engine failed or loss compression, so I know there is a problem somewhere and likely many problems to find.
 

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150 to 130 ish is a large drop in compression. The pto having the white'ish plug and lowest reading makes sense. Note the texture on the ground strap. That tells me there was something funny going on in the combustion. Very technical, I know :lol: As far as I am concerned, that is detonation. Fortunately it didn't accelerate to pre-ignition otherwise it would have melted the forged pistons. It probably would have melted had you not had prior 2S failure experience and kept on the throttle to clean-up a bog. The only thing that cleans is the bank account lol
 

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Are those the ECS plugs ?
I seem to remember RK Tek recommending not running them. Although that was some time ago.
The exhaust color is interesting. Due we know what isoflex looks like burnt in the exhaust. First thing that comes to mind is sulfur. I think it's still in gas, maybe not ?
 

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Discussion Starter · #6 ·
The plugs were quite new actually maybe 100 miles on them. They are ECS's but I don't recall Kelsey mentioning anything about not running them. I may need to give him a call lol.

As for gas though, I had just filled up with 93 and this was the first time the sled has seen Ethanol (10% or whatever they have at BP) in a couple years maybe 1,000 miles. I assume it was from the grease burning off but maybe something to do with the fuel too? I have my pipe off nearly every week to get at other stuff and never noticed that color.
 

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100 miles is far more than needed to get color, probably 99 more miles. I can't imagine how an ECS plug could cause a lean running engine. The main two problems that I familiar with different plugs is 1. Misfires, and 2. incorrect heat range. For example if the engine has an extremely lean range, then that range would fare better with a larger gap and a strong ignition to spark the gap. The 800R is the leanest running carb that I know of.
 

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I am not as experienced as some of you guys but if it was the isoflex burning, that color in the pipe is coming equally from both cylinders so it would have to be burning it in BOTH cylinders. I suspect it was something from the fuel.

100 miles on those plugs makes me think it was running lean.
 

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Good point on checking which side the yellow tint appears in. To me it looks like the mag side, but the picture isn't clear enough to really tell.
 
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