Topic: Solving Clutch Drag?

[sammermpc]

My '72 CB500 has all of the symptoms of clutch drag (missing neutral while warm, tough to shift while idling, easy w/ the motor off, etc.).

I've replaced the lifter rod and adjusted the lifter, as well, and I think it's pretty good. I have checked the friction and steel plates -- but at this point, I'm thinking of just replacing them.

Is that the logical next step? Anyone have any recommendations? I've read the Barnett kits are more appropriate for racing rigs -- and not great to boot -- but I'm having a tough time making sense of the many options on Ebay. I'm concerned if I buy one set of friction plates and another set of steel plates, they won't match up correctly.

[TwoTired]

Are you using the stock clutch lever and perch?

Have you measured the flatness of the steels and frictions in the clutch?
Have you measured the thickness of the clutch steels and frictions?

Are there any discoloration in the surface of the steels?

[sammermpc]

Are you using the stock clutch lever and perch?

Is this what I call the lifter rod? I purchased a NOS stock one and I measured it -- fell within what I'd seen posted in the forums.

Have you measured the flatness of the steels and frictions in the clutch?

Yes, I used a plate of glass and a feeler gauge. They seemed fine.

Have you measured the thickness of the clutch steels and frictions?

Yeah, they were within spec, though some were getting close to being too thin.

Are there any discoloration in the surface of the steels?

They were discolored but I sanded them up w/ some fine grit sandpaper.

I posted pictures on this thread: http://forums.sohc4.net/index.php?topic=137070.msg1545121#msg1545121

[iron_worker]

On my cousin's 500, part #3 was cracked which allowed it to bind up off to the side instead of only moving axially and engaging the push rod. Check that part closely for cracks/damage.

IW

[sammermpc]

I've rebuilt & greased the whole lifter mechanism, along with a new OEM clutch cable, so I think that's OK. I'm getting better at adjusting it too, and I'm definitely seeing the benefits there.

[TwoTired]

Are you using the stock clutch lever and perch?

Is this what I call the lifter rod? I purchased a NOS stock one and I measured it -- fell within what I'd seen posted in the forums.

No.  The clutch lever is on the handle bars.  It is what determines the clutch cable travel distance.  If the throw distance has been changed, you might not be getting enough travel for the clutch mechanism.  Then in order to adjust for full engagement, the clutch will drag at the disengagement position.

Have you measured the flatness of the steels and frictions in the clutch?

Yes, I used a plate of glass and a feeler gauge. They seemed fine.

What size feeler gauge?

Have you measured the thickness of the clutch steels and frictions?

Yeah, they were within spec, though some were getting close to being too thin.

Possibly best to renew those now while you have it apart.
If it starts slipping, you'll be back in there anyway.

Are there any discoloration in the surface of the steels?

They were discolored but I sanded them up w/ some fine grit sandpaper.

Sandpaper marks will contribute to drag until they are worn smooth.  How long have you run the sanded discs.  Doing drag race starts can wear them in faster.  This also wears down the frictions, though.

What I was looking for were heat discolorations where the steels may have changed their temper.  They can do so in specific places which changes their expansion characteristics, allowing them to warp when hot, and cause drag because their warped average thickness has increased.

[dusterdude]

Did the bike sit for a prolonged period


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[sammermpc]

If the throw distance has been changed, you might not be getting enough travel for the clutch mechanism.  Then in order to adjust for full engagement, the clutch will drag at the disengagement position.

I didn't change it, but maybe the PO did. Looks pretty normal. Also, shifting is fine when the motor isn't running, if that's any indication.

Sandpaper marks will contribute to drag until they are worn smooth.  How long have you run the sanded discs.  Doing drag race starts can wear them in faster.  This also wears down the frictions, though.

It's only been a month or so -- and I haven't been riding much. But I'm riding from Boston to Iowa in a month or so and trying to take care of any loose ends that I can before I go.

Did the bike sit for a prolonged period

Nope, I ride a couple times a week.

[sammermpc]

So to wrap this up -- assuming everything else has checked out, it sounds like the next step is to replace the springs & the friction disks -- at least, that's all I've got to go on.

Does anyone know if PN 22201-KY2-000 is a drop-in replacement on a '72 CB500? They're available from Partszilla (http://www.partzilla.com/parts/detail/honda/HP-22201-KY2-000.html) and elsewhere, but appear to be for later models.

David Silver also sells a clutch kit -- does anyone have experience with that?

[RevDoc]

Your symptoms sound just like the same ones I was seeing with the '78 550K I just starting to rehab. after PO left it sitting for several yrs. Hard to hit neutral when warm unless stopped. Easy to find with engine shut down, etc. Oil level was low I first got it. Drained and filled with a combo of Quaker State & Valvoline that I had on the shelf. Still had problems. Then I found the following in a list of tips put together by HondaMan(Thanks,James!) and noted the two brands specified. Dumped the oil, refilled with straight Castrol and it shifts like a dream now. Best to err on the side of caution anyway as TT suggests re marginal parts if you're planning a long ride.

500/550 Clutch Tips
« Reply #5 on: February 15, 2006, 10:40:42 AM »

First word: GREASE! The clutch lifters on these bikes wear more because there is much more shifting going on. Grease those lifters!

We tried all kinds of clutch mods. The stock clutch would wear because of the slanted cork block faces, which were designed to let the oiled plates squish out the oil slowly and ease the engagement (part of the "smooth 4 effort" of the 500). Heavy-handed throttles then caused plate heating and warpage, making the faces engage less, then they wore quickly.

Barnett jumped in with their superior friction plates, but they were thicker, so their sets had 1 less plate pair than the Honda set. Result: same grip, less life. Even worse: the Barnett cork bits wear the oil pumps, causing low oil pressure after a while.

Solution: today, the plates are available with square-cut cork faces. Find these and use them. And, replace the steel ones, too. They're warped if you have 10,000 miles on them, believe it. Also, DON'T run Valvoline or Havoline oil. These excellent oils over-lube the plates and make them slip. Instead, use Castrol (best) or Torco (next best) oils. Castrol and Honda worked together in the 1970s to get the right blend: trust 'em.

If you're drag-racing: get the Honda slanted-cork plates and put them in backwards. Put the steel ones in backwards, too. They'll grab like a spline clutch and break the rear wheel free at the green light.