1973 cb 750 starter clutch

[maybe73]

When the bike was cold the stater would engage no problem. Once the engine was warmed up, I would hit the starter button and the starter would turn but the clutch wouldn't engage. Kick starter worked fine when needed so I rode most of last summer that way. Fast forward to this season. I bought the clutch rebuild kit and the 20 mm tool to remove the rotor. Easy repair, hell I even saved the cover gasket. Once apart everything looked new, but I had the new parts so in they went.
Same symptoms. When cold engine, the clutch works. With hot engine the starter just spins. So I took the cover off again and held the reduction gear shaft in with the handle of a screwdriver and hit the starter button with the run switch off. Oil plug came out and oil pumped out, but on big deal. Every time I hit the starter button it worked as it should. The starter clutch gear, reduction gear and the small starter gear look perfect and fit and line up correctly. The surface of the clutch gear that the clutch rollers ride against look perfect. So maybe the bearing that is in the starter clutch gear? Any thoughts? Thanks in advance.

[Re-run]

Wow, well I have never had a starter issue so I can't say for sure.

So I will just throw this out. When warm, have you tried using a screwdriver to jump the contacts on the starter solenoid? Just to rule it out? Jumping it removes the solenoid totally from the equation. It may be that it is starting to go out and is not operating right when the engine is warm, since the starter sits in that heat.

Maybe the solenoid is working well enough for cold starts, but not warm. Engines start better when warm, usually, but motors are more efficient when not hot.

Like I said, never had a starter issue but if I did, I would try this. Just to rule it out, if nothing else.

[maybe73]

Ok Re-run, so you're thinking that when everything is hot, the solenoid is delivering enough juice to spin the starter but perhaps not fast enough to engage the clutch. That's an easy test so I will give it a try. Thanks.

[Re-run]

Essentially, yes. The idea is that the solenoid is on its last leg and when it gets warm, as the left side does from rectifier heat, its internal resistance goes up and it stops working properly.

Make sure you do the test when the engine is hot, or when it doesn't start right.

[maybe73]

Yep, you may be on to something here. Will test after work.

[maybe73]

I finally had the chance to ride some decent miles over the weekend. Can't get the starter clutch to act up in any scenario, hot or cold. Tried it dozens of times. So I will leave well enough alone. Thanks.