oopssorry like i said never had time to read the whole thread
you say you got power to the starter im assuming you have no cranck live to the throw switch wire normaly little push on wire on the start soliniod?
if you have this then i would say it must be earth as this is all it need to turn over firing is a diffenet matter all together but if it bumps ect then it should be ok
test this and let us know
Tony