1. Tooth to tooth loss. Pop in gear, move backwards/forwards [whatever is easier] so you move to any gear tooth than the one you're at now. Starts fine for a few times and then the compression brings that gear back in the same position sort of speak and the problem occurs again. You now assume the clutch basket with that big gear having a lost/worn tooth. And with that said you replace both parts so fresh cut gears move into fresh cut gears, not some worn gear about to enter half way in kind of... don't cheap out in other words.
2. Starter clutch collapse. This is where the one-way starter clutch locks one way, spins the other way. Say you saw a camel toe pass by you as you started the bike up. You held the button in too long and you snap out of it when you hear a strange noise at the engine. The reason for the one way clutch is the freewheeling design so you can watch camel toe all day and not hurt the starting system. So if there is a constant clunk or the spinning up of the starter, we look at this part as a variable.
3. Running clearance. Say a third variable would be the starter assembly moving away from the gear to gear input. We could rule this out or the bolts would have walked out already and would have been obvious with that magnet kicking in. So we can rule out the electrics, not the motor making a magnetic field to send the shaft out and engage the one-way clutch and all that.
Thanks in advance. 
Thanks in advance. 
Something isn't right