Hi all just just recently changed piston and liner and after building engine up it wont start ive got 100 psi on all cylinders and got spark ive tried 2 sets of plugs dizzy and roter arm are nearly new. when engine turns it doesn't even attempt to fire i taken top carb lobster off its wet through with petrol and it some times chucks smoke out when trying to start. ive built many enigines and had 5,s for about 15 years this one has got me scratching my head any suggestions.