Topic: Yet Another CB500 Clutch Question

[Dr. Frankenstein]

I'm working on this 1972 CB500 Four, and can't seem to get the clutch cable dialed in; I thought I had it adjusted right, but something is amiss because when I try to pull the clutch in, it just stops, and won't do that little 'give' you feel when you pull in a normal one...pull the clutch lever and it feels like it won't go any farther - did I have it adjusted too tight?? it still has the original pushrod, and the ball in the adjuster, and I thought I had it yesterday but the whole clutch action seemed too 'weak' or something so of course I had to keep screwing with it.

I'm using a new clutch cable that is the same length as the old one; with the clutch side cover on, I can pull in the clutch at the handlebars, but the lifter itself only moves slightly - it's loose/it will go in and out, probably about 5 mm - but when the engine is buttoned up and you pull the clutch in, it's like the clutch lever just STOPS, and won't go any further. The clutch plates themselves are free - I cleaned them a while back (3 or 4 months ago), but do they get sticky again over time? I'll clean them again and see if that does anything... 

Also, I am torquing the clutch plate bolts to what the book says - 5.8–7.5 ft-lbs - would that have anything to do with it?

From what I have gathered though, these early 500 clutches seem to be a bit problematic - I'm assuming my problem is something I'm doing (or not doing!), but I wanted to field this question and see what you guys say.

[bryanj]

Torque has no effect adjustment of mechanism has a big effect and there is a bulletin on how to, that is the big round adjuster in the sprocket cover

[Dr. Frankenstein]

Hi Bryan - Yes, I know, I was following those instructions - loosening the bolt, turning the adjuster clockwise until a slight resistance is felt, then back it off an eighth of a turn and tighten the nut - but it just felt weird, it wasn't hard at all to pull the clutch lever in. Maybe I was tightening it too hard...? Do you know the link for the bulletin?

[bryanj]

Somewhere in a service letter there is a procedure with the modified adjuster that has a small notch on one end of the big slot which has to be within a certain position on the circumference, if i can find it i will copy it for you.

NOTE:- there are both sevice bulletins and sevice letters which are different

[Dr. Frankenstein]

Huh - yes, I'd like to see that. As far as I know though my adjuster is not modified...is that common on '72 JDM 500's?

[bryanj]

It was not a recall just a mod ifcuztomer complained

[Dr. Frankenstein]

Just out pf curiosity, I found two different torque settings for the CB500 clutch bolts: the internet says 7.2 - 10.1 Ft lbs, while the actual CB500 manual I have says to torque the clutch bolts to 5.7 - 8.6 Ft lbs... I googled 1972 CB500K, but could that larger torque value be for a 550?

Using the first number, I set the clutch bolts on my 500 to a median of 8.4 Ft lbs before I discovered the 5.7 - 8.6 value; what kind of difference will this make as far as the clutch is concerned? 

Also, since I set the torque on the 1972 CB500 to 8.4 Ft lbs, it is in spec, albeit on the outside edge of the torque values for that bike - would that make it harder to pull the clutch lever? (I would assume so...)   

[bryanj]

As i said the torque on the bolts has no effect at all as you are tightening the plate down onto the 4 pillars from the back plate

[bryanj]

I found the service bulletin attached is a picture, hope it helps

[HondaMan]

When the clutch lifter has developed the "stop" inside it, which is right where the PO had it set for (50?) years, the soft metal of the outer housing of that lifter grows up a "bump" right at the end of the screw's travel. This prevent the screw from going further, which it also needs to do, to lift the pressure plate. You can pull out the clutch lifter from the case, clean all that old goo out, and see the "bump". I use a Dremel with a porting bit on it (cylindrical cutter head, about 5/16" diameter) to flatten off the distorted edges of it, then use a rounder cutting head to smooth it out so the moving screw thread can get past the 'bump'.

Another way to fix this is to use a slightly longer pushrod, like in the 500 engine that is sitting in my shed at the moment: that fancy pushrod appears in my CB500/CB550 book. I didn't make it: someone who is a very good welder made that one. It is about 1/4" longer than the OEM rod, so the screw lifter is riding in a previously-unused section of the lifter's housing, and feels like brand-new parts.

A 3rd (but REAL frustrating) method is to use different clutch plate thicknesses in the clutch. This will move the clutch's "disengaged" position slightly. It involves tricky math like: replace 3 normal plates of 0.138" thickness with 4 of the [Vesrah] 0.107" thickness to slightly move the disengaged spot of the lifter more toward the engine's left side, so the lifter's screw won't hit the 'notch' inside the lifter.
Tricky, but it works well enough to get home again from 1500 miles away...

[Dr. Frankenstein]

Bryan - according to that bulletin, I do have mine adjusted correctly...

HM - I cleaned everything out thoroughly and didn't notice anything out of the ordinary, not that I was looking for anything at the time. The clutch pushrod is whole and complete, and after messing with it a bit I believe I got it set correctly - at least it feels right, or 'righter' than it did. But I don't think I'll definitively know until I get that piston problem of mine fixed. 

[HondaMan]

We sometimes used a "trick" we called "the 350 fix", which was a 1/4" ball bearing inside the hole where the clutch rod fits. I sometimes found these already in these sorts of lifters (Honda and other makes), making me think they were "factory parts", but couldn't find a Honda part number for them. So, I went to Bower Bearing (who made Timken's bearings in the town where I was) and bought a handful of "undersized 0.250" balls" which were those ball bearings that got over-ground in manufacturing and were used for making "extra clearance" ball bearings (or cheap ones). One ball inside the hole moved the adjustment point away from the worn groove, making for a smoother clutch.

Today they call these tricks "hacks"?

[Dr. Frankenstein]

Yes, mine has the ball bearing in the hole where the clutch rod goes; I fiddled with the adjusters on both ends and think I have it, but now I have to hurry up and wait to get the primary chain problem fixed first. Gonna be a long summer.

[Deltarider]

[...] turning the adjuster clockwise until a slight resistance is felt, then back it off an eighth of a turn [...]

Eight of a turn?! That's not right. In my manual it says: back off 3mm (which happens to be an eighth of an inch).
Do NOT use a torque wrench for the four bolts. Here's why: http://forums.sohc4.net/index.php/topic,169731.msg1970275.html#msg1970275

[Dr. Frankenstein]

Yes Delta, you're right - that's what I meant (I must've been thinking about carbs...)...and so other than using the manual torque values for the clutch bolts, what do you suggest...? How tight should they go?

[HondaMan]

I use about 70-80 in/lbs on the clutch bolts. They don't come loose, even when barely tightened..

[bryanj]

If you disconnect the cable at the lever then pull the cable upwards from the casing can you feel the mechanism stop when it touches the pushrod?