I just put a rebuilt engine into my ski. I have fuel, spark, and 150psi compression on both cylinders, but she won't start even with starting fluid. There is fresh gas in the tank (when the motor blew last summer, I drained the gas).

She cranks fine but won't light... any thing I may have missed?

 

How blue is your spark and where is it firing BTDC or AFTER could you be mising a key way and the timing be off. Take a timing light and see about when it fire compared to the stroke of the piston.