Dirt bike guru WANTED yamaha yz125

[brokeit]

Hi I have just rebored my cylinder and put in a new piston, now I can't get my bike to fire there is spark but it wont fire. Heard it could be a reed valve? Does anyone have any ideas. Thanks

[Motu]

The other two things required for combustion are fuel and compression,and being a 2 stroke I'd like to add vacuum in there too - check those and get back.

[XTC]

I see you rebored it and fitted a new piston.... Did you also fit the rings? :) Did the 96 YZ125 have a steel bore?

[laRIKin]

Since it was going before and most things being the same.
Are you sure that you put the piston in the right way around?
And is the plug getting wet?