Hi everyone

We got our little 05 Predator 50 3 years ago. It's always been hard to start, but if you squirted gas in the carb it would fire and run like a top. The kids have outgrown it so in order to sell it I thought I would fix that nagging problem. The stock piston showed blow-by all the way around so I ordered a new jug/piston/ring kit from ebay. After I installed it the bike wouldn't fire at all. I replaced the crank seals because I figured the blow-by would have taken them out. It has good spark, gets fuel and has no blockage in the exhaust. The stator tests out fine as well. It will not go above 90PSI on the compression test. I have tried three different head gaskets, properly torqued the head bolts (19nM from the Polaris manual) and even replaced the head studs in case they got stretched. It gets the same poor compression with the old jug/piston as it does with the new set. The ring gaps are well within spec. The head looks fine, flat and no obvious cracks.

I'm at a total loss as to why the compression is so bad. Does anyone have any ideas?

Thanks

 

Unless it's one of those Chinese kits that allowed too much piston to cylinder clearance to begin with.Plus I've heard that some kits may be for a different stroke length. If the piston reaches the top of the cylinder that shouldn't be the problem though. A leak down test may help as the problem could be a case leak, base gasket,seal leak or even a head gasket leak even with all new parts.

 

Thanks for replying OPT. I've watched that video and debated doing the test. I will get it done this weekend and report back!