Very sudden starter problem!?

Bike is a 1982 KZ750H3. Went out to ride today after the bike had been sitting a few days. Battery is fully charged, headlight bright, no new wiring, everything fine...except the starter will not turn. The starter relay just clicks. Turned everything off and tried shorting the relay studs. Starter turned just a tiny bit each time I shorted it. Until today this starter spun the engine fast and strongly!

Now, a few days ago I pulled the sprocket cover to seal a leak. I had not ridden it since then until I tried today. Could I have done something unseen to the starter while I was in there? Any ideas? Thanks!

Polcat, have you added a booster battery to it? Make sure if jumping you use another car battery with the car turned OFF. If it still won't turn it, then again go across the solenoid posts. If still not turning check your battery cable connections, apply the jumper negative directly to your engine case. Still not turning, then put the positive jumper to the Load side of the solenoid, that's the cable that goes down to the starter motor. If it still won't turn then it sound like a starter motor problem. Having the sprocket cover off should not affect anything, unless you pinched the main starter cable between the cover and engine. You would see smoke coming out of that area as it burns off the wire insulation.

Happened to me once that when I hit the starter button it was just dead. No clicks, no nothing. Turned out to be a problem with the electrical switch at the clutch lever on the handlebars. This is just inboard of the clutch cable and is activated by pulling in the clutch lever. You can pop it out by looking underneath and pressing in a little springy detent. The fact that your solonoid is clicking makes me think this is probably not the cause/solution. Might be worth checking before you tear into the starter motor, Hopefully something simple either way.

Thanks for the tips guys. A friend across the street has a high amp 12volt charger with a starter setting. Since I strongly suspect the starter, we hooked the positive of the charger directly to the starter side of the relay, and tested by tapping the ground against the engine case. This bypassed everything but the starter (and the cable of course). Same thing, a very slow failed attempt to turn. This tells me that, barring a seize up in the engine itself, or the cable being bad, it's the starter. Anyone disagree?

I'll start pulling the starter tomorrow and check the cable as I do. Anything special I need to know about pulling the starter?

Well the way I pull my starter is to first pull the chrome cover, then the sprocket side cover, then the 2 bolts that hold the starter to the engine. It will wiggle up and to your right, while the gear end goes left, it will then come out and go down towards the sprocket area where you can then disconnect the cable. You can disconnect the battery if you feel safer, but there should be no power to the starter cable without the solenoid being engaged.

It my be a good idea to pull your Ignition cover, then using the larger 17mm nut on the crankshaft end turn over the engine by hand with the KEY OFF, making sure as you mentioned it is not a mechanical issue.

Tried to spin the engine by the 17mm nut. It spins fine.

Well, it's not the starter. Pulled it today and tried it directly from the battery. It spins hard and strong! Now, since I got the same no spin condition when I jumped over the relay (meaning the relay is okay), it seems there are only two possibilities.

One would be the cable from the relay to the starter, but it shows good continuity. However, it was a little oily around the cable mounting ring. Could cause resistance I guess.

The other (which I suspect is the problem) is the ground. I found a thin coating of corrosion on the flats where the starter gets bolted to the caae. Also on the mounts of the starter itself (these are where the starter and case get mated together with bolts) and on the bolt threads. So that's probably a ground problem.

I plan to clean everything up and try it again. Any of this make sense?

The starter motor needs a good ground for power transfer. If it's corroded, take some fine sandpaper(400-600 grit), abrade the mounting places followed by a thin coat of the siver anti-seize.

I'M WRONG!! It is the starter! I decided to spin test it a few more times before putting it back in the bike. The first time it spun fine, but the next few times...nothing. Then after turning it by the front gear and tapping it a few times it spun, but very sluggishly and slowly.

So I take it apart only to fine a kind of black oil gelly all over everything! The brushes were clogged with the stuff and it had a burned oil smell (as one might suspect). There are two ring type gaskets around the starter case, which were hard and half broken away. I had fixed an oil leak near the starter a few months back, so I'm sure the starter has been slowly filling with oil for years.

Still, no actual burnt parts or damage (other then the brushes being worn nearly away). This is a Mitsuba 8M-6208 starter.

So my next question is where can I find a rebuild kit for this thing? Or should I start looking for a good used one?

Three choices:

1.Take the starter to the local electrical starter rebuilding places.

2.Haunt E-Bay.

3A. www.mawonline.com/newsite/rick_s_motorsp...-starter_brushes.htm

3B. www.cyclewareables.com/pages/street_star...kits/startmtrkit.htm (not sure if the website is still viable)

Thanks for the links MFolks. After a good cleanup, seems all it needsa is brushes (and some seals). Thanks all for the responses!