Topic: Clutch weirdness today--advice sought

[Shane72]

Hey all,

1972 CB750K, bike is pictured in avatar.  Stock engine, clutch, and everything else relevant to the question, as far as I know.

Clutch cable replaced with new less than 2 years ago, and while it's been many years, I have broken several clutch cables in my day and this feels and sounds a little different...

Symptoms/situation:  Short ride today, bike warm, running perfectly, thankfully near the house.  As I was turning onto the highway, I noticed a clear rattling noise (maybe a slight grinding noise, but not like transmission gears grinding at all) from the right side of the engine, accompanied by a small but noticeable loosening of the clutch cable.

I eased on to the road, and shifted through the gears gently, wondering if the cable was about to fail, and staying in the right lane to take the exit that was only about two blocks ahead.  As I slowed down and worked back through the gears, the cable continued to get looser, with too much freeplay at the lever.  The rattling noise appeared briefly once or twice more, and as I slowed to a complete stop at the light, the engine died as I let out the clutch in neutral.

I restarted the bike in neutral, pulled in the clutch, let it out again in neutral, and the rattling noise again appeared just as the engine died, as thought the noise was being made from something that stopped the engine.

This all happened in the space of 30 seconds or so.

At that point I decided to take a moment to think, and a guy with a Suburban and an empty trailer pulled next to me and offered to haul me and the bike the 4 blocks to my house--I love Iowa!

So as I'm thinking about what the problem might be, It occurred to me to post this up and see if anyone has an educated guess as to what my problem might be.  I won't have time to pull the clutch cover until Wednesday, so rather than think about it alone, you all are welcome to help me focus my thoughts and action on this.

The current status is that the transmission shifts just fine, the clutch lever is really slack with freeplay, but the clutch can still be disengaged with the lever to some degree.  The cable doesn't feel like it is broken, but the adjustment is definitely out of control.

The only two things I can think of off the bat are:

1.  The clutch cable is indeed toast, and is hanging on by one cable strand, or

2.  The adjustment mechanism at the clutch itself has come loose

The accompanying noise is what has me leaning toward the adjustment locknut having come undone, because a cable break is usually quiet in that regard.  Also, the engine stopping when the clutch is engaged in neutral seems to be effected by a way-out-of-adjustment something--not a cable break.

Well, what do you think?

All the best,

Shane

[Don R]

Check the clutch lifter to see if it has lost it's ball or come apart inside.

[Shane72]

Ok, so I found the problem...

Pics:





Broken clutch pressure plate bolt...

Got it removed, new bolts in, now for the reassembly...

Having a bit of trouble feeling the adjustment bolt seating on the pressure plate bearing when trying to set the main adjustment--any tips for a smooth adjustment process?

Thanks,

Shane

[madmtnmotors]

now for the reassembly...

Having a bit of trouble feeling the adjustment bolt seating on the pressure plate bearing when trying to set the main adjustment--any tips for a smooth adjustment process?

Thanks,

Shane

I have the same problem since the adjustment here happens so infrequently I forget how easily the adjuster will compress the bearing plate. Get a smaller screwdriver, back the adjuster all the way out, then turn it in, using just two fingers, until you feel the adjuster "touch" the bearing. At that point turn it out and back in again, getting the feel for the moment of contact. From there you just back off 1/8" to 1/4" turn (depending on who you use for your source of specification here), tighten the locknut, and you're done.

[Shane72]

Figured out what I was doing wrong...

It wasn't the adjustment procedure so much as the fact that I had not made sure that the pressure plate studs were in the fully extended position when re-installing the 4 bolts that hold the moving plate (and the clutch springs) in place.

What wound up happening was that somehow I had the plate tightened down as if maximum disengagement was happening all the time.  There was no way that the disengagement mechanism would ever adjust properly--in fact, the pushrod could never even touch the moving plate within the allowable adjustment range.

So I just removed and replaced the plate again, this time making sure that the threaded stud mounts were at full extension, and gingerly started all four bolts, taking up the slack just like it's supposed to.

All good now, easy enough fix, no apparent permanent damage, and I got to practice my bolt extraction technique again today!

All the best,

Shane