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smokinwrench
04-28-2004, 10:32 PM
I learned a little 2 stroke lesson this week I thought I would pass on. I over hauled a Polaris 350L. 350 2 stroke liquid cooled motor. It was bored 0.020 and everything left stock. I put it back together and it wanted to run away (full throttle). I messed with it some last night and new I was missing something obvious.

Tonight I went out and removed and cleaned carb. Got it running and regulated the throttle by sticking a rag over the carb. I let it die and went to restart and I finally seen it. I seen what I thought was a spark, but I think it was a backfire down in the crankcase. I found that I had a crack in the case. I had checked the thing over 100% on the bottom because I knew I was getting a lean mix causeing it to run away. This crack is on the top of the case.

I added a picture. I hope I got it loaded. You can see where the piece of case is stuck up just a little. I just wanted everyone to see this and maybe it would help someone out with a problem.

Macs
04-28-2004, 10:36 PM
leaking bottom end pressure does cause this. i have found that no matter what adjustment you do it will not fix it. i build gt750 race bikes and 9/10 that if the motor runs full throttle it is a cracked case or blown crank seals.

holmstrom
11-17-2005, 07:12 PM
That sounds like the problem im having.