Honda cb700sc clutch issue

[Ghall001]

I recently purchased a honda cb700sc from a friend. He rode it quite a bit about 6 months ago and I know it ran fine. I recently purchased it from him and after getting the carbs cleaned out ok it now runs strong but the clutch which is hydraulic is slipping. It did not do this when parked. I have bled the hydraulic clutch and changed fluid in it but it still grinds going into first gear and you have to take it easy going from gear to gear or it slips badly. If you take it easy going to the next gear before getting back into the gas the clutch holds fine. I have not changed the oil yet.

Any ideals on what could cause this? I believe the clutch is good. If you get rolling and let the clutch out first it will blow the back tire off very easy.

[Novelldude]

I'd say clutch slave cylinder needs work. If it's like by cb650, there's the master up on the bars, and a slave that sits down below the carbs. The clymer has instructions on how to bleed that one too. If you think it's still good, then the next obvious choices are...

1. I'd make sure your steel plates and springs are still within spec.
2. If you break into the clutch, while there, I'd replace at a minimum the friction plates.

Try these guys.

https://www.partsnmore.com/cat_index.php?model=cb750_sohc&category=engine

For 4.00 bucks a plate, it's cheap to change out the friction plates.

Given what your saying about it running strong, I doubt you have bad plates, but if you're tear into it, it only makes sense to spend the 20 bucks it'll take to put it together with new bits.

Good luck,
ND

[Black_peter]

The CB 700SC and the CB 650 Nighthawk are 99% the same.
If you are sure the clutch is OK, and I don't get why you think that, non MC oil could be causing the clutch to slip...

Clutches slip when you gas it in third gear or try to start off in third, and can..
CBs (every one I ever owned) sounded like it was self destructing going into first.
Grrr-Clunk!!

[StevieB]

One thing I learned about bleeding clutch systems, at least on 80's era Hondas- use a block of wood to keep the clutch lever from going all the way to the bars- you want to stop it about 2/3rds of the way into it's travel. Don't ask me why this works, but it does.

[Ghall001]

I will try the wood first before opening it up but thanks for all the input so far

[Ghall001]

When I do open it up and change clutches should the springs be changed

[Ghall001]

UPDATE

The suggestion about the block of wood and bleeding it halfway worked for me.
The clutch is working very well now I believe. I was able to break the back tire loose in third gear while moving about 45 mph and first traction is a real problem (with good metzler tires). Also gear to gear changes are slip free now. I still have the very annoying clunk when you shift into first gear whil stopped but seems thats not an uncommon thing.

Anyway thanks for the suggestions and help.

[StevieB]

Yeah, that wood block idea is a winner. I just have no IDEA why it works...

Congrats on the sucess.