Starter spins but doesn’t crank the engine

[Doc_Qanai]

[size=14]I’ve got a strange problem. Two weeks ago I rode the bike (1981 R65) to meet some some about 10 miles away. The bike started up fine and ran fine. When I went to leave to return home I hit the starter button and I could hear the starter spinning rapidly, but it wasn’t turning the engine. I had to push start it in order to get home. Thinking that perhaps the Bendix drive had gone bad, I pulled the (Bosch) starter out and replaced it with an almost new Nippon Denso starter from my R100RS whose engine needs to be rebuilt. After putting everything back together I tried the starter and it worked right away. The next day it worked and I rode to meet some people about 15 miles away and when I left to return home everything was still fine. Now, tonight I go down to the bike to start it up and it turned the engine a couple of times, but, before it could fire, it stopped turning the engine and the starter was just spinning very rapidly. I could understand a bad Bendix in a starter on a bike with 90K miles on it, but what would be causing this to happen with an almost new starter after it had already started several times? Any ideas? What should I check?

Doc  [/size]

[tvrla]

It's obviously not the starter.

And since it works sometimes, and sometimes not, it can't be the clutch carrier came unbolted from the crankshaft.

Sounds to me like the starter gear came loose from the clutch carrier.

There's really nothing else that makes sense to me. Whatever it is, the transmission will need to come out.  

[Bob_Roller]

Try removing the rubber plug on the left side of the engine, the 'timing hole', look in there with a flashlight and try to see something out of the ordinary .

Stick a screwdriver in the hole and see if you can move the starter ring gear .

Try removing the starter and look the ring gear over .