Mine would do something similar to this. Turned out I had a corroded battery terminal, and it wasn't letting the battery fully charge. Depleted battery couldn't turn the starter more than two or three turns. This went on for a few months until the battery just didn't have enough charge to turn it over more than once. And that just wasn't enough to get the bike to start.
Cleaned the terminals, installed a battery maintainer, and now all is good. Fires right up.
Well the battery is fine and the terminals are always kept clean, thanks. ( I even put silicone di-electric on them). The starter turns fast enough but stops dead after a few turns with that clunk noise, then I have to press the starter switch again.
BTW what is a battery maintainer?
It's a charger. It will fast charge if your battery is low, then go into a trickle state to keep the battery topped off. Picked mine up at Wally World for about $40. They're great to have if your bike stays parked for any amount of time. When I say "installed," it comes with detatchable leads that you can permanently mount to the battery. Then you just plug the lead into the charger. I routed mine to the other side of the bike by the tool tray. Just open the cubby with the key and plug it in. Keeps me from having to break out the allen wrench to get to the battery and use the clip-on leads. Pretty handy.
I may have found my own answer, if I do not throttle when starting:
Defective Starters - Twisted Bolts - Bad Starter Clutch (See next item)
It appears the prime "suspect" in the dreaded "clunk" leading to twisted starter bolts (and also to starter clutch failure) is the improper use of the throttle (right hand!) when starting the bike. Advancing the throttle causes the TPS (throttle Positioning Sensor) to "misread" and to cause a kickback - the full power of which is directed at the flimsy internal structure of the starter. See the next two items on proper starting technique - and avoid the problem.
Also appears that an incorrect setting on the TPS is a major contributor to the dreaded clunk - either on starting or on engine shutdown. Included in the TPS section below is an excellent article, with pix, on how to check the TPS setting and how to adjust if it is out of the preferred range.
Click here to jump to that TPS check & Set article.