2000 cylinder on a 1995 yz 125

[smrmx]

I just bought a yz 125 that has a 2000 cylinder on it with a 1995 piston in it. My problem is I can't get this thing to start.It has good compression,spark ,fuel, and looks like proper timing.It acts like its going to hit and start but will not.
Eric or Rich I know you guys are the best.Do I have to run a newer piston with boost port to run with the 1038 bearing ?


I am lost on this thing please help

Thanks

 

[CRazy250]

i think the piston is the problem, i believe the 2000 piston has an intake window and the 95 piston does not

 

[Eric Gorr]

The piston window won't hinder the starting unless the piston is backwards. The rectangular window should face the intake side of the cylinder.