Hello and thank you in advance for any help,this is a great forum with an incredible amount of knowledge. I recently rebuilt the top end of my 96 polairs xpress 300 due to low compression. I sent the cylinder to summit offroad in florida where it was bored .040 over and fitted with a new namura piston and rings. I assembled the engine and disabled oil pump and ran a mixture of 32.1 during break in as instructed by machine shop. The bike ran great but after only about 4-5 hrs of use it died and wouldn’t restart. After performing some basic checks I checked compression and only have 90 psi. Any ideas as to what could have caused such premature failure. I performed the break in procedure as recommended by machine shop as well. Only thing I haven’t checked yet is the crankcase seal, however if the crankcase seal blew out wouldn’t that cause much lower compression than 90 psi?? Again thanks for any help!