1981 Honda CB750C Multiple Issues

[ScottinNY]

Ok. I have an 81 CB750C, 7500 miles, all stock. Many issues. Maybe someone can lead me in the right direction.

Issue 1. I couldn't get the bike to idle down. No matter what I did, the idle stayed at 3000. I pulled the carbs off and rebuilt them. I replaced the intake and airbox boots with new ones. Put it all back together and it started right up. Shut the choke, set the idle screw, and perfect 1000 idle. Problem is...everytime I stop, it jumps up to 4000. I lower the idle screw, and its fine until I ride and stop again..then it jumps back up. Sometimes it SLOWLY idles down, usually it don't.

Issue 2. The battery wont stay charged. the more it runs, the more the battery drains. I used a multimeter, and at idle, the voltage drops. Give it gas, and it jumps back up..let go and it drops. Good battery. If it dies and wont start, I let it sit for 20 min, and then it starts.

Issue #3. There is a rattle sound behind the clutch cover. when I pull the clutch, it goes away. release the clutch, its back. Only at idle. Higher idle, I don't hear it. I pulled the cover off, all looks good. Any ideas?

 

[cbsavage]

It looks like there's nobody here to solve our problem. I have the same high Rev problem. See my post in '79 '81 fuel section High revs after warm up.

 

[tommycarl]

I assume you've checked to be sure the throttle cable isn't hanging up... if not, give that a closer look. Have you checked closely for vacuum leaks around the insulators (carb-to-head "boots")?

 

[cbsavage]

The thottle cable is working ok, and no I haven't checked the carb boots for leaks. They could be dried out from sitting so long outside at the mercy of mother nature.

 

[thughes0025]

Dose anyone have an idea what his charging issue is.. I got the same problem with mine...charges when on throttle up to 14.5 at idle its like 11.8ish....I can ride it 45 min no problem till I turn it off...it won't start...wait 20min fires right up....any ideas will be greatly appreciated

 

[brettp]

Your battery might be dying. Have it load tested.
Note, these bikes may not charge the battery during idle at all. They don't spin fast enough at idle to generate sufficient voltage to charge it. Cars work differently.