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1999 Polaris scrambler piston melting

I am working an a 1999 polaris scrambler,I have replaced the piston 3 times and everytime the exhaust side of the piston melts, when I replace the piston i make some fuel adjustment,but nothing seems to make a difference,I also am not sure about the exhaust pipe it did have a hole in it which I welded.Is there such a thing that the exhaust does not have enough back pressure?

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Hi Hpenner- We are a Napa store and garage, in Alberta, Canada, and we work on many brands and types of ATV's. First of all, is yours a two stroke or four? If it is a two stroke, does it have oil injection? You will need to make sure that is working (once you have it running)
1) what are you having done to the engine when you replace a piston, is it bored out with new rings, etc?
2) if it is a two stroke, the crank seals may need to be tested, they can fail, cause the engine to run lean and take out pistons like you are describing. The engine needs to be removed and taken to a reputable snowmobile or racing shop- they can seal all the ports, and there is an adapter that screws into the spark plug hole, then the engine can be pressure and vacuum tested. soap solution can be applied on the seals to see if they leak, in extreme cases we have submergred the engine in a water tank with 3-5 psi pressure to see where the leak is. It is a very simple problem, but very often overlooked, no one thinks of the seals, but the whole crankcase is essentially the intake, so it has to be sealed to run properly..

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Posted on Jul 07, 2009


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