Topic: Starter Broken? Replacement Compatibility?

[MattFreeman]

I'm working on getting my CB750 F1 back on the road after a complete rebuild and I think my starter is broken.

When I hit the switch the spindle spins great but does not extend to engage the gear as I assume it should. Figuring that I need to replace it can I use a starter from another 750?

[Tews19]

sounds like what I recently went through with my 550. It's the starter clutch. A bit trickier to get at on a 750 if I recall correctly.

If you hit the starter button and you can hear it spin but nothing engaging in the engine than most likely it is the start clutch. Not the starter. But to be safe pull the starter motor and see if the teeth are gone on it.

[Jerry Rxman Griffin aka MuthaF'er]

Spindle spins but does not extend to engage the gear??

Is the starter motor spinning up properly? These are pretty tough motors and rarely do you see one not turn.

Is the gear on the motor's shaft engaged with the larger gear that's attached to the back of the charging rotor?

Yes and yes?!! So far so good. If so you have 2 possibilities. 1) the rotor was not torqued down properly and is spinning loose of the crank or 2) the starter clutch has problems.

So, make sure your rotor is torqued down to about?? 70 ft lbs ?? then if it's still not engaging the crankshaft remove the rotor and replace the 3 sets of clutch parts.  ie rollers, springs and spring caps. You'll need to slightly drill out the divots/staking that were put in the 3 screws but thats easy then take an impact driver to them. This usually does the trick. If once you've done all this and it STILL spins freely then a less obvious and less frequent problem is the large gear itself. The 'face' the rollers engage gets worn and the surface can get irregular causing an intermittent issue of not catching the crank. If it feels 'less than round' shall we say or irregular shaped then you may want to replace it with a better used gear or perhaps (untried as far as I know) have it turned ever so slightly to round again.

And yes, all the 750's will interchange. 
 

[MattFreeman]

You're absolutely right Jerry. I left out the part where I didn't apparently have the rotor torqued properly. I think I forgot to check it once the drive was hooked up and able to provide some good resistance allowing me to get proper torque. That's the problem with taking 4 years on a rebuild.

After sleeping on it I started to think that this may be the only issue. Last night I thought that this had caused an issue with the starter but now I realize that putting it back together properly might solve the problem and your response is helping.

Here's to hoping I at least torqued the con rods properly...

[Jerry Rxman Griffin aka MuthaF'er]

Excellent news! Don't ask me how I know