Hi, I have a polaris 2006 trailblazer 250 2 stroke. Had it rebuilt with new pistons, rings, joined, new crank bearings, rod bearings etc. Has about 2 hours on rebuild and slowly lost compression and down to 87psi. Their is tons of carbon buildup...]http://



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any ideas of what caused this? I also rebuilt the carb, did I have the adjustment screws wrong and was it running roo rich or too hot?

thanks

 

What clearance was the new piston to cylinder? Did you premix the first tank of gas 50/1 as the manual says? I suppose since you had the bottom end done,new crank bearings along with crank seals. The cylinder should still have signs of cross hatching if it was bored and honed properly even with 2 hrs riding and it doesn't..That may be the problem area. Measure the bottom of the piston and also the cylinder and see what clearance you have.

 

Did you test the compression before initial start-up? I'd be curious what your baseline was...