Clutch slipping

[maybe73]

1973 cb750k. When accelerating hard at about 5000 rpm, tach jumps about 500 to 1000 more revs and I can feel it slipping. Back off throttle a little and it grabs again. So I took clutch apart. Clutch spring free length measures 1.27-1.28" for all four, fsm standard=1.2575". Friction disk thickness measures .137" on all 7 disks, fsm standard=.1347-.1409".   So, glazed friction disks?  Or weak clutch springs?  Before I purchase disks and springs, I'm wondering if I am missing something. I have no way to measure clutch spring load and clutch cable  free play is not the problem, I backed it way off. This problem has gotten progressively worse. Thanks in advance.

[Re-run]

The plates could be an issue. It could be the springs. It could be the oil.

Start easy, what oil did you last put in? You should be using a 10-40 weight oil. If you look on the back, it should NOT say "energy conserving", I have not run into a 10-40 that does say that, but double check.
I use rotella 5-40 synthetic oil and it works perfect. It is also jaso ma2 certified. Some people really care about that.

Also, are your steel plates all facing the same way? If you look, they are stamped out and have an edge. The edges should all be facing the same way.

I don't have the manual right now, at work, but make sure springs are in spec for length, I think there is a weight listed too. So make sure they hit that weight. You may need to check with a shop about testing this.

Springs are not to expensive though, but get the honda springs. Barnett springs are good, but they make the lever really hard to pull. I also recommend honda plates, but barnett plates work well too. Just make sure you soak the fiber plates for 24 hours in the same oil you use. And that you assemble everything facing the same way.

Oh, when you checked free play, did you adjust down by the clutch too? Some times a person forgets that spot and only does up by the lever.

[maybe73]

Thanks Re-Run for the reply.
Oil is Pennzoil 10-40. No friction reducers or energy conserving. Not even full synthetic. Three changes with this oil, never more than about 1200 miles.
Springs and plates all measure well within fsm limits, I listed the specs in first post.
Yep, clutch cable was loose at both ends.
I believe all plates were facing same direction.

Cycle x has clutch plates with gasket and kick starter shaft oil seal for $49 and springs for $14.
Any experience with these? $63 plus shipping is doable.
 
Since this problem has steadily gotten worse over the last 400 miles, I am thinking that glazed plates and weak springs are the culprit, even though they measure correctly. Don't know spring compression strength, just length.

Thank you again. Any thoughts and comments are appreciated.

[TOOLS1]

Did you adjust the at the clutch adjuster on the clutch cover, or just at the cable?
I have used the Cycle-X parts, plates, and springs. The plates seem to be thicker then stock. I had to remove a fiber plate and replace it with an extra steel plate in order to get the clutch to adjust.
TOOLS

[maybe73]

Yes, I even loosened the clutch release lever at the clutch so that there was no tension any where and the small spring at the lever is in tact also.

I will have to remember about what you said TOOLS about your trick in removing a friction plate and replacing it with a steel plate as far as cycle x plates go. Thanks for the tip. Of coarse I have no extra steel plates, but I will cross that bridge if needed. So then at what section did you put 3 steel plates together? Middle of the stack?

[TOOLS1]

It's two steel plates together, anywhere in the stack. Shiny did a writeup on clutches awhile back. I'm sure a search will find it.
TOOLS

[maybe73]

Thank you TOOLS, now I understand. I was thinking that you just pulled one fiber plate and replaced it with a steel one causing 3 steel plates to be together. Duh on my part. Great write up on clutch replacement. Big thanks to SHINY RIBS.

http://honda-cb750-s.456789.n3.nabble.com/How-to-change-and-adjust-a-clutch-SOHC-td4040391.html

[maybe73]

Well I finally got new clutch plates installed! What a tremendous difference it makes. Although the old plates and clutch springs measured well within Honda specs, the new plates are freaking smooth. Standing starts, shifting, especially from 1st to 2nd have become almost effortless. Even neutral is so much easier to find. Wish I had done it sooner. So any one that thinks they have glazed or old and brittle plates, take my advice and change em. A big thanks to SHINY RIBS for a fantastic tutorial on clutch replacement. Super easy job.  

http://honda-cb750-s.456789.n3.nabble.com/How-to-change-and-adjust-a-clutch-SOHC-td4040391.html