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Old 03-15-2010, 09:50 PM   #1
SERIALSTUNTER
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Default IT 200 Blown piston /melted cylinder...how do I avoid this again after rebuild?

Hey there, I bought an 86 IT 200 (2 stroke) last summer and I didn't get 30 miles and blew a hole in my piston. I'm ordering a top end kit for it (the bottom end feels tight).

I'm going to bore over 50 thou. I would just like to get some expert opinions on how I can avoid this happening again. My mix was a little on the rich side so that didn't cause it. Is there any screws on the side of my Mikuni carb that can cause a high rpm lean condition?

I'm going to pressure test my crankcase before I rebuild, and the read valve block looks as good as new. Any tips would be great...I really want to actually ride this bike this summer it's in really good shape besides my piston meltdown situation. Thanks.
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Old 03-16-2010, 04:35 AM   #2
longride
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Your fuel mixture was lean. Check your spark plug after running it for a short time. If it looks bone white, you have a problem.
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Old 03-16-2010, 04:57 AM   #3
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Melted pistons are usually caused by a lean condition. You need to run the bike wide open and then check the plug as LR said. You might have the needle too high which would cause a rich condition in the mid-range while at the same time too small a main jet will cause a lean condition in the high range.

I'd suggest buying new stock jets. Restore the carb to the factory setting with the needle in the middle notch and adjust from there. Who knows what the previous owner did? Obviously it wasn't good.
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Old 03-16-2010, 05:39 AM   #4
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All of the above. I assume the stock airbox and filter are in place, right?
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Old 03-16-2010, 07:45 AM   #5
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Detonation can hole pistons too. But it sounds like a combo of bad jetting/timing off. Air leaks can cause this too, check the mag side crank seal & cylinder base gasket for leaks. IT's were pretty much indestructable.
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Old 03-16-2010, 08:29 AM   #6
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Make your own pistons with spoons and '54 Chevy slugs. It worked for Anthony Hopkins.
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Old 03-16-2010, 08:31 AM   #7
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Quote:
Originally Posted by mscuddy View Post
Detonation can hole pistons too. But it sounds like a combo of bad jetting/timing off. Air leaks can cause this too, check the mag side crank seal & cylinder base gasket for leaks. IT's were pretty much indestructable.
Speaking of 2-strokes Mr. Cuddy, how's your schedule look for a FL visit? The Yermamahaw needs you!
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