yamaha qt weak spark

mike /

I have a 1980 yamaha qt50.For three weeks cant get running.The spark is to weak just a little polk when holding it not enough to fire.I replaced flywheel,stator,coil and still weak spark.checked all wiring cleaned ground.i replaced stator assembly twice still no change.All lights work except headlight.but was told headlight has nothing to do with spark on this unit.I also looked up and seen some came with keyed switch that has start,run.Mine only has on and it does have off run off kill switch checked that too.they said had to be on start to start run it wont start but i dont know when they started that and if mine had been changed by someone?Is headlight causing this or maybe short in keyed switch because i notice if i turn key half way when kicking oil light flashes but no spark until turned all they way.I am at a dead end.also new plug

dont know how to bypass ignition switch it has 5 wires just to check it.have cut end of plug cable no change please help thanks

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