Drain for power valve cavity

my motor had a new crank put in it and that screw was not put back in , i had put the amount of oil specified in the motor and did not know it was not there . i started the motor and it blew smoke out of the screw hole but no oil had come out and now i can not even get the engine to start or even make any noise .could that have burnt out any electrical part i tried a different cdi box with the same result!any help is appreciated thanks mike .

The power valve resonator tank may accumulate some oil from the exhaust.  Smoke will come out of this hole even when the power valve is closed because there will be some exhaust that leaks by the clearance between the cylinder and the power valve spool. 

Transmission oil cannot enter this resonator tank that is built into the front of the engine cases unless there is a crack in the cases.  Running the engine with or without this screw will not affect the power, the jetting, the transmission oil level, or the ignition, but will only make a mess on the engine due to a small amount of oily exhaust coming out of this hole.

Your engine will not run because you have other problems and not because this screw was missing.

I do not understand why anyone would remove this screw when rebuilding the engine.