Topic: Clutch issue (grabs a bit)

[Stoli]

CB750 K4

Newly rebuilt clutch with CycleX friction and steel plates. Used 7 friction and 6 steel. The steel plates are smooth, not dimpled.

FSFSFSFSFSFSF

Soaked plates in oil (Rotella T 15W-40) overnight. All friction plates have the angled slots and are installed in the correct orientation. Inner drum was modified as per Hondaman's suggestion - drilled more holes and countersunk on the inner surface of the drum. Cable adjusted per Honda manual.

Have about 150 miles on it so far and the clutch is very grabby at launch. Hard to keep the bike from shuddering. Sometimes (but not always) a bit difficult to switch from 1st to N or 2nd (shift lever is hard to lift up). Also noticed that with the engine off and the bike in gear, after squeezing the clutch lever in, the clutch doesn't release until I force the bike forward or back, then it will move freely. Let out the clutch then back in and same occurs.

Any thoughts? Searched the forum but didn't find any conclusive answers. Anyone else used the CycleX plates? Is it just a case of wearing them in a bit?

CycleX tech support - non responsive.

[martin99]

Any wear on the clutch basket 'fingers'? (don't know what else to call them!). I usually dress out the notches with a file when I replace a clutch. It's conceivable your new plates might be getting caught up when engaging/disengaging if wear is pronounced.

[Stoli]

Thanks for the reply. I don't remember any significant wear on the basket but in all honesty, I didn't take a hard enough look at that. I plan on pulling it when I do an oil change in a few days and will take another look.

[bjbuchanan]

Did you adjust the clutch again after a nice hot run? After rebuilding them you Gotta ride a little to get that perfect setup, make sure everything is oiled up and been functioning for a bit

[Stoli]

I did re-adjust after about 100 miles but there wasn't a noticeable difference.

It occurs to me that 5 of the 6 original (dimpled) steel plates were in good shape and only 1 was warped a bit. As I mentioned, the new plates that I put in are smooth. I am thinking about putting the 5 dimpled ones back in with just 1 of the new smooth ones to complete the pack. Do the dimpled ones slip a little easier because they hold oil or do I have that wrong?

[Dunk]

I have a CycleX clutch in mine for a few hundred miles now. I also did the extra holes in the basket, as well as oil pump orings and seal and countershaft oiler orings. Got the clutch used, not sure why PO didn't want it but supposedly was not used long. I have no issues with it, no more slipping and it fully releases, or about as fully as any SOHC4 will. 90% of the time it feels like no drag at all and very easy to find neutral when stopped, no more clunk/lurch when putting it in gear either. Occasionally it'll feel like a very slight amount of drag but nowhere near my old slipping stock clutch.

I did readjust after about a 50 mile ride while everything was still good and hot at operating temp, before that it was good but not perfect. I think it's critical to readjust the clutch hot to get maximum push on the pressure plate while still ensuring the clutch is fully released. Also switching from a 40w to 50w oil helped ensure that last bit of drag was gone and considering how hot these things get when pushed hard on a warm day I think 50w is better.

Your problem sounds like maybe there are some grooves or nicks in the basket inner or outer slots/teeth holding things up. As oldskoolnuts said, hit it all lightly with a file and run your fingers over those areas to feel for anything but smoothness.

[Stoli]

Thanks for the reply. Couldn't find a lot of feedback on the CycleX plates so it is good to know they are working well for you. In another thread, Hondaman is talking up Bey-Ray 20W-50 oil, so maybe I'll give that a shot. At this point, I don't suspect the oil weight though since the issue occurs regardless of engine temp.

[Stoli]

Thought I would revisit this thread to bring it to a conclusion. I took the bike out and drove it like I stole it for about 60 miles and the clutch smoothed out quite a bit. Then I did an oil change and rebuilt the clutch with the dimpled steel plates except I used two of the smooth steel plates together in the center:

FSFSFSSFSFSFSF

Then took it out again for another 60 miles of maniacal riding and things seem to be settling in with the clutch. The lever is a bit stiffer now but that makes sense since I added another plate. So, I think this is just a case of letting the friction disks wear in and using the right oil with the right level of zinc.

Soooo .....  this does bring up another quesion though. What is the recommended range for the thickness of the entire clutch pack? There are a lot of threads on this forum regarding individual friction disk widths, etc. but none address what the combined width should be. My clutch seems to work about the same with 6 steel plates as it does with 7 steel plates. The difference is the amount of space left on the inner drum for the compression plate to sit. Does it matter? Do I need to post a pic to explain what I am taking about?

[Dunk]

Not sure on total stack height, but the thicker you make it the less room for things to float and be free when you pull it in.  For what it's worth the stack that came out of my K1 (and dragged) is about 1.435" thick. I did not measure the CycleX stack but I would assume it's very close and probably slightly thicker from not being worn.

[Stoli]

Do you remember how many of the CycleX plates you used?

[MCRider]

The addtl plate clutches have fibre plates that are thinner than stock, to make up for the addtl plate(s). But whenever you introduce variables, things are variable.

My 9 plate APE stack was slightly thicker than stock. More than just wear would account for. So the amount of room allowed for it to disengage is less.

[Stoli]

Makes sense. And your comments sort of highlight my dilemma. There are so many different plates out there and different model years and different variables that one can introduce, I would think that there might be some guidance as to a min and max height of the total plate assembly. Or, even better, the min and max space that is left over on the inner drum after all the plates are assembled. That space being the amount that the inner drum has left over for the compression plate to slide into. Is it possible to build the stack so wide so that when you pull the clutch lever in, the compression plate extends beyond the end of the inner drum and disengages from the teeth?  I'm sure you can build the stack too short so that the compression plate bottoms out before it makes contact with the stack.

[MCRider]

Makes sense. And your comments sort of highlight my dilemma. There are so many different plates out there and different model years and different variables that one can introduce, I would think that there might be some guidance as to a min and max height of the total plate assembly. Or, even better, the min and max space that is left over on the inner drum after all the plates are assembled. That space being the amount that the inner drum has left over for the compression plate to slide into. Is it possible to build the stack so wide so that when you pull the clutch lever in, the compression plate extends beyond the end of the inner drum and disengages from the teeth?  I'm sure you can build the stack too short so that the compression plate bottoms out before it makes contact with the stack.

Right, my worries exactly. I did your last thing by only installing 8 plates thinking that was enough. Plate pak bottomed out before squishing and slipped at anything more than idle.

I added up the width of each plates per stack, didn't keep the numbers. But the 9 plate stack was about 1mm thicker than stock. It appeared we have 3 mm to play with. All very unscientific, but my clutch works now.

[Stoli]

The more I think about it, the more I think I should remove that extra steel plate I put in there. Here's a stupid question - do you need to drain the oil from the pan before you remove the clutch cover or will the oil level be lower than the bottom of the cover in its normal state? In the past, I have always worked on the clutch with no oil in the engine.

[martin99]

Just remove the cover with the bike on the prop stand. You will get a few drops if anything at all.

[Don R]

Most of the oil should be in the tank.  I believe the clutch lifters and covers came in varying heights and travel. One more variable. There may be multiple correct pack thicknesses depending on the model.

[Stoli]

First off, an observation - it was insinuated earlier in this thread that the taller your plate stack, the less room for your clutch to disengage. I believe that is a false statement. Correct me if I'm wrong, but the space that your clutch plates have to disengage is dependent on clutch lever travel and when properly adjusted, a plate stack height of 37mm would have the same amount of wiggle room as a 38mm stack. In other words, just because your stack is shorter, doesn't mean the clutch lever moves the pressure plate further away from the stack.

Anyways ...

It was a cold, rainy day today and I was bored so I thought I'd try to put this issue to rest. Here is what I found:

Note: this is a clutch from a CB750 K6

Pic #1:


Pic#2:


The pressure plate, shown in the first pic, has 6mm of travel on the inner drum (clutch center) before it "bottoms out". When the pressure plate bottoms out, the space between the inner drum and pressure plate is 35mm. So your plate stack needs to be at least 35mm or your clutch will slip. As noted above, if your stack is over 41mm (min + 6mm), the compression gap, as shown in pic2, is zero or less and the pressure plate can't mesh with the splines on the inner drum. Not sure what happens at that point but probably not a good thing. I made the term "compression gap" up by the way. Not a technical term.

I have sort of an interesting dilemma on my clutch because the total plate stack height with 7 CycleX friction discs and 6 steel plates is 36mm which is only 1mm more than the point that the pressure plate bottoms out. Seems like it wouldn't take very long before my clutch would start to slip. On the other hand, if I add another steel plate, the height is 38mm which leaves my compression gap at 3mm. Not a lot of room left. I have ridden the bike in both configurations and they both work.

So, the question at hand is how high (or wide depending on how you are looking at it) can your stack be before you force the pressure plate beyond the top of the inner drum and run the risk of it disengaging from the splines when you release the clutch? Well, there is a lot that comes into play there (clutch lever travel and cable stretch to name a few). On my bike which has a stock hand lever and a new Motion Pro 02-0124 cable (stock -3”) the cable travel is about 16mm (hand lever full out to lever squeezed against the hand grip). That 16mm translates to 3mm of travel on the release shaft (the thing that moves the pressure plate to release the clutch).

Now, because of the way we adjust the clutch, the pressure plate will not travel that much. It would if you didn't back off the adjustment screw 1/4-1/2 turn and left zero play in the lever, but once you do that, the movement of the pressure plate with the lever squeezed to the grip is closer to 2mm. So that gives me 1mm before the pressure plate comes off the splines. Good enough... I guess.