How does a starter clutch work?

[KEITH KRAUSE]

I should know,but I don't. I've never had to work with one.How do they operate and if they are failing, what are symptoms? Thanks, KK.

[Clone]

Not sure of the exact method of function. But when they are starting to fail you will crank-the starter will then spin freely-there will be a clunk and the engine will crank again. Repeat above with higher frequency until the engine will not turn but the starter will spin quite well.

[mark]

Hey Keith,
The starter spins a large gear (the biggest one when you look at the left side with covers removed) by mean of an idler gear. The idler gear is used to correct rotational direction and achieve proper spinning speed by means of "gearing down". The large gear itself is not attached directly to the crankshaft, and does not spin while the engine is running during normal operation. The large gear has a collar on the left-"out"-side that fits into a roller clutch assembly. This assembly is a "one-way" mechanism and will only lock/engage when rotated in one direction and unlocks/disengages when spun in the other direction. The roller clutch itself is bolted right to the rotor part of the alternator, which is connected directly to the crank. The starter spins and engages the clutch mechanism (through the large gear) causing the engine to rotate. When the engine finally starts its rotating speed quickly overtakes the relatively slower starter motor. It is in this "speed overtake" that the clutch disengages, and stops rotating when you release the starter button. The design of a roller clutch allows you to "accidentally" hit the starter when the bike is running and not damage things too much (no grinding like when you do the same with your car, or in my case my girlfriends car 8)), as no teeth engage or disengage on your motorcycle it is only three rollers that apply pressure to the large gear collar (inside the "one-way" mechanism).
Anyhing that does not engage right off the bat or makes "clunking" noises should be looked at. Each of the three rollers has a spring and plunger to go with it and if the springs break or the plungers are stuck the clucth will not work properly. A good thing about this system is that if it does fail it normally fails in the disengaged state (would suck to have it lock up on the road) and the starter motor will simply free-wheel under "no load" like Clone stated. One more reason I love my kickstarter as a backup.


Mark
_______________

1978 gs750
31, XXX km
slightly modified 8-valve engine (Custom oil filler cap!!)
old kerker exhaust

[kz]

The starter clutch is bolted on the rotor with three bolts.

The three bolts came loose on my GS 1150 1984 causing one of the bolts to share off.

be sure to use lockite on the bolts when you mount the starter clutch.

[KEITH KRAUSE]

Thanks Mark,for the excellent reply! Merry Christmas! KK.

[mcycle-nut]

I too, had the three screws shear off. Didn't do any major damage, I just repalced the whole rotor and starter clutch with one I had kicking around. Unfortunately I wasn't very observant. It appears there are two different charging systems on my particular bike, and you can't really mix them. The used rotor I put on had a different number of magnets in it than the one I took off. I found this out once I put it together and got no charge and talked to a mechanic. Then I had to take it apart again and put the correct rotor in. Works fine now. 8)