I just replaced the piston on my 07 yz450f, 13 to 1 proX, and I cant get it to start. I have the bike timed to the last mark on the fly wheel when rotated counter clockwise the singular "I" mark after the two I-I mark. thats where TDC is also. The cams are aligned with the head as per manual or as close as they get with the head. 13 pins from 12 O'Clock to 12 O'Clock. I torqued the cam caps with a snap on torque wrench. However, the bike wont start just occasional backfire. I know I'm getting spark and gas at least. Bike is kicking over but with allot more compression than with the old piston and rings. Any ideas as to whats wrong?