Topic: Clutch metal plates toast?

[zabzob]

CB750 clutch slipping since late last year. A few seasons of riding on it, including a trip from the west coast of Canada to the prairies.This is the clutch that came with the bike, which had sat for about 17 years unused. Not surprising that it's toast. Included is a shot of the new springs on the left vs old on the right. Fair bit of spring fatigue, I guess.

I have new friction plate soaked in oil, read to go in. Looks like my metal plates are in bad shape though. Should they look like this? Can I just polish them up a bit? Or are they fine?

[rotortiller]

If it is deposits from the fiber plates clean it off. If it's rust toss them. If it is rust I'd wonder about the rest of the engine inside.

[jonda500]

I don't think springs fatigue that much - the new one is 3/4 of a coil longer than the old one? Aftermarket part?
+1 to ditching the rusty plates. My 2nd 500 came to me with very rusty clutch plates - they fell into many pieces when I got them out! There are rust scales on some other parts inside the engine, but nothing has failed after >2000miles
John
edit- 'nothing has failed' - err well, actually not exactly nothing, as I have had multiple rusty valve spring breakages. I have replaced all of them now though, so that's stopped happening!

[eigenvector]

I'd toss the whole thing.

Truthfully I don't think the rust and pitting really matters that much as long as they're flat and within tolerances - but if they're that corroded I really doubt they are.

As for the springs - they're really cheap, why keep them and worry about it?

[TwoTired]

I'd sand off the rust.  And/or metal prep bathe them.   Then measure the thickness remaining.  If within tolerance, use them.

Brand new plates have divits in them to retain oil.  Rust pits would do that same thing.  It's a matter of whether you want to risk going in again to replace if operation is not pleasing to you.  If you really don't want to go back inside, get new plates.

Cheers,

[Jimray23]

Replace the steels, theire not that expensive and its one less thing to worry about.

--------------------------------------------------
Jim
1979 kz1000b ltd
    stage 3 cams
    pod air filters
    4-1 open exhaust(no muffler)
    full rewire
    dyna-s ignition
    dyna 3 ohm coils

[zabzob]

Hit it with some sandpaper and it looks like it's friction plate material. On some of the metal plates you can see the grooves where the friction plate was touching it. Friction plates were pretty worn, as you can see.

I'll get some more sandpaper to clean them up and put them back with the new friction plates. Thanks for the input everybody!

[NobleHops]

We formerly swept new steels on a concrete floor to rough them up before installing them. I've abrasive blasted them too. Most important that they be flat IMO.

There is a spec for the minimum free length of the clutch springs, and if those are new ones to the left then I'll wager your old ones are way under it, and that is the source of your slipping.

[zabzob]

Sandpaper is cleaning them up. Some are pretty clean, some have significant old friction material stuck to them. Anybody know anything can just dissolve the friction material away?

[NobleHops]

Green scotchbrite and acetone will probably do the trick. Soak them, covered, before you start scrubbing. Use a fan to keep the vapors at bay.

[PeWe]

There are different springs, some are shorter. CB750 clutch changed during the years.
My bike sat 20 years, the clutch springs were still OK. I tried vintagecb750 harder springs that were shorter and harder than my old High performance springs to CB750-76. My clutch hand preferred my old longer springs. I have now changed to Barnett harder springs since engine has bigger bore.

Important to use Motorcycle oil, car oils have often anti friction additives that cause clutch slip.

[madmtnmotors]

Hit it with some sandpaper and it looks like it's friction plate material. On some of the metal plates you can see the grooves where the friction plate was touching it. Friction plates were pretty worn, as you can see.

I'll get some more sandpaper to clean them up and put them back with the new friction plates. Thanks for the input everybody!

Hey everybody, take a close look at the "sanded" disk. The disk that is being presented here is a friction (fiber) disk. These disks with the tabs on the outside are friction disks and should be discarded and replaced. The "steel only" disks will only have teeth pointing inwards. Scuff them clean with a scotchbrite pad, measure their thickness and reuse them if within spec...

[Bailgang]

Hit it with some sandpaper and it looks like it's friction plate material. On some of the metal plates you can see the grooves where the friction plate was touching it. Friction plates were pretty worn, as you can see.

I'll get some more sandpaper to clean them up and put them back with the new friction plates. Thanks for the input everybody!

Hey everybody, take a close look at the "sanded" disk. The disk that is being presented here is a friction (fiber) disk. These disks with the tabs on the outside are friction disks and should be discarded and replaced. The "steel only" disks will only have teeth pointing inwards. Scuff them clean with a scotchbrite pad, measure their thickness and reuse them if within spec...

D'oh!!! Good catch.

[zabzob]

Hi madmtnmotors,

That friction disk was not sanded by me. It came out of the bike that trashed! I'm only cleaning up the metal disks without the tabs.

[madmtnmotors]

Hi madmtnmotors,

That friction disk was not sanded by me. It came out of the bike that trashed! I'm only cleaning up the metal disks without the tabs.

Ahhhh... the narrative with the picture made me think you were sanding on the friction (fiber) disk. Those friction disks are toast! Clean up the steels and the measure them for thickness and warpage. I'll bet you might have one or two steels below spec. The innermost disks (both fiber and steel) tend to see the most wear.

[Bailgang]

Hi madmtnmotors,

That friction disk was not sanded by me. It came out of the bike that trashed! I'm only cleaning up the metal disks without the tabs.

Ahhhh... the narrative with the picture made me think you were sanding on the friction (fiber) disk. Those friction disks are toast! Clean up the steels and the measure them for thickness and warpage. I'll bet you might have one or two steels below spec. The innermost disks (both fiber and steel) tend to see the most wear.

If your friction discs are that bad then you may want to consider dropping the oil pan and cleaning it out because I imagine you have some crap from the clutch floating around in there.

[zabzob]

I've decided to get new steel plates. Didn't really want to spend any more on the bike this season, but it's taking a long time to clean them and I have a long trip coming up soon. I'd rather not chance that these are out of spec (can't measure right now) or that residual friction material on the steel plates will chew up the new friction plates. When I have time, I'll clean them and if they're still in spec I'll either keep them or sell them here.

[ekpent]

Hi madmtnmotors,

That friction disk was not sanded by me. It came out of the bike that trashed! I'm only cleaning up the metal disks without the tabs.

Ahhhh... the narrative with the picture made me think you were sanding on the friction (fiber) disk. Those friction disks are toast! Clean up the steels and the measure them for thickness and warpage. I'll bet you might have one or two steels below spec. The innermost disks (both fiber and steel) tend to see the most wear.

If your friction discs are that bad then you may want to consider dropping the oil pan and cleaning it out because I imagine you have some crap from the clutch floating around in there.

I was thinking the same thing so I will give it a +1.

[Doo Bee]

Call Cycle X and get a complete clutch kit---steels and friction disc. Just use your old
springs with a shim or get new stock springs. YOU DON'T NEED RACING SPRINGS!!
They are waaaaayyyy too stiff. Bike will shift better and go into neutral like it should.
Good luck!!

[zabzob]

Got the new metal discs. They are genuine Honda, and do not have impressions on them like the old ones. Should I sand these up before I put them in?

[jonda500]

Soaking them in engine oil is recommended, I haven't sanded new ones but I think it wouldn't matter if you did...
John

[ekpent]

Got the new metal discs. They are genuine Honda, and do not have impressions on them like the old ones. Should I sand these up before I put them in?

  You would think Honda would have the appropriate finish on them out of the box.

[PeWe]

Glass bead the metals.
Stronger springs are not hard. Barnett CB750 springs are comfortable for hand and wallet.

[flybox1]

Got the new metal discs. They are genuine Honda, and do not have impressions on them like the old ones. Should I sand these up before I put them in?

  You would think Honda would have the appropriate finish on them out of the box.

No doubt.
Id scuff the metals before use.  They need texture to hold oil.  Emery cloth or wire wheel
Oil soak the new fiber plates before installing.
Hondamans clutch basket oil mod would be a good thing.

 

[zabzob]

Thanks for the advice everybody. Friction plates were soaked in motorcycle oil for days while I waited for new metal plates. Scuffed the plates up with some 600 grit paper. New clutch is in, following the helpful directions here:

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

Super nervous about breaking the lifter plate, so I worked slowly. Just did a test fire last night but it was too rainy to take it for a ride. I'll take it out today and let you all know how it feels to have an in-spec clutch