250sx help

[Atc 123]

I just finished a rebuild of the top half of the motor i went to start it wouldn't so i checked every thing noticed when i kicked it over air comes back through the air box or where it sounds like its comeing from so help any ideas

[125Mmadness]

If its coming out during the compression stroke then your valves aren't seating and you need to lap them.

[fabiodriven]

You don't necessarily need to lap your valves. You would adjust the valves first and go from there. Are you sure you timed the valves correctly?

[shortline10]

Timing is off , cam lobes pointed down with the top cam sprocket bolt at 12 o'clock , piston top dead center and flywheel mark set on T

[Atc 123]

Ok thanks guys timeing was off but another problem occured i used the kick starter and it went all the way down then came all the way back up and hit the tire did it slide off the gear cuz the spring still winds up?