Just started to get this problem when motor is in neutral it runs awlsome then when i put into drive it shuts off cant figure it out looking for some help on this

shuts completely down? a bad shift cable will cause shift interrupter to stay in the spot where it shuts off motor momentarily while shifting. this is an alpha with shift on the exhaust riser? watch the little spring-loaded lever while shifting. there are lots of other possibilities, like a blown drive, but this is a start.