I came across something and thought of you, this guy thought he had starter problem and changed several times without improving.(96")Turns out that the compensation sprocket is the week link here and caused grinding, clunking. Was going to add cr s then he learned about this problem. $250 se big twin comp upgrade and one hour solved all his problem,he's happy as a clam.
Hope this helps

 

Have been running some high compression engines for a while, the dreaded kick back becomes present when battery supply voltage isn't full charge at the starter. When a battery is new, good cables a starter will turn a high compression engine easy because that old saying "a body in motion tends to stay in motion" when the cranking slows down the dam thing will kick bag and a ugly sound comes in.
Since the problem just started it would be best to check cable connection as low voltage will "machine gun" the starter drive, if all checks out with connections and a fully charged battery then most likely the starter clutch is toast. Have a All ***** 1.4 like mentioned alot in this thread with 6 or 7 seasons on it, put the same starter on a 127" with a new clutch drive and can start it without compression releases during a cold condition. Check those connections first before assuming a starter but if needing a starter the All ***** are hard to beat.