no start

07 yfz 450 high compression with stock engine So i changed out the cylinder and piston on the quad after i had smoke leaking out of the exhaust head. Ended up changing out the piston and cylinder. Wanted to do it soon anyway. Put it all back together and got two very loud pops on start up...

so to start with I have a vortex ecu and a gt Thunder manual idle air control. This all started long ago and in the beginning the quad would randomly shut off then not restart for a few hours. After I let it sit it would start no problem, then it slowly got harder to cold start, Now the quad...