What is the problem, does it:
Not Fire?
Fires but won't run?
Runs but stops after a short time?
As it is a port controlled engine the timing depends on the position of the ports being as in the drawing. A few basic checks:
Does it have 'bouncy' compression?
Have you eliminated air leaks in the crankcase?
If you hold a match or lighter in front of the exhaust while turning the engine do you get a flame and if so what colour?
If you turn the engine with the spark plug resting on the cylinder head do you see a strong spark as the piston approaches top dead centre?
