Time for a new clutch

[93Bandit]

Yep, I'm curious about everything I'm not sure about... Thanks for helping the community possibly learn something.

Of course, anything to give back to the community that has been an invaluable resource for me.

 

[93Bandit]

I never saw anything near that worn on any oil clutches I've seen. The fibers always look kind'f new. The oil clutches just don't seem to ware hardly at all. Years ago I did quite a bit of st., and some track drags. Always rode (slipped) the clutch taking off, but no ware, just busted hubs and broken plates.

You might have convinced me to try sanding them... We'll see how they measure and how lazy I'm feeling once I get them out and inspected.

 

[Cipher]

Yeah, it was a kind of mix of flakes and fibres.

On a few boy racer drag sessions I had my clutch plates stick solidly together.
its harrowing to pull in the lever only to find the clutch won't release.
running out of runway frantically trying to gear down to neutral.
all the cool kids laughing at your post run gesticulation and lamentations.

 

[93Bandit]

On a few boy racer drag sessions I had my clutch plates stick solidly together.
its harrowing to pull in the lever only to find the clutch won't release.
running out of runway frantically trying to gear down to neutral.
all the cool kids laughing at your post run gesticulation and lamentations.

Yikes, that sounds like an experience to remember.

 

[93Bandit]

I torn into the 850 yesterday. I took the clutch plates out and measured all of them. I measured thickness at 4 spots on each plate, 12, 3, 6, & 9 oclock.
Spec per the OEM manual for the frictions is 0.106-0.114" with the limit being 0.094", and steels spec is 0.080" with no limit specified.
My clutch plates measured the following:
-The friction plates measured 0.107-0.109", most being 0.107".
-The steels measured 0.075-0.077", most being 0.077".

So my frictions fall within spec, although all are at the low end. All the steels are below spec, but only by ~0.003". None of the steel plates are scored or look worn. Only one plate has 3 areas of discoloration due to heat which you will see pictured below. Also, I dried off the frictions well and gave them a close inspection. They definitely have a shine to them so I think they are glazed. I also noticed that when wiping the oil off them the friction material was flaking pretty heavily and felt somewhat brittle in places. See pictures below.

Here's the only steel plate showing signs of overheating. It's not warped and still has a smooth even surface so I will be reusing it.


Here's a few pictures of the frictions. You can see the shinny hard surface.




Here you can see where some of the friction material flaked off.


Also, when I took the clutch plates out I noticed the basket was loose. Come to find out, the basket hub nut was very loose, the only thing holding it on was the washer. So I need to take that apart to see why it came loose. Hopefully there's nothing damaged/badly worn and I can just retorque it.


I think between the age of the clutch, the brittle friction material, all the plates measuring at the low end of spec and the glazed appearance, I am going to opt for installing new friction plates. My biggest fear is the material being so brittle, I don't want that coming apart and contaminating the engine, clogging oil passages etc.

Let me know what you guys think!

 

[93Bandit]

Be sure to keep us updated.. Also, I've always heard of plates glazing, like mentioned up ^^^ there. I've don't remember hearing what causes it, but have heard the thing about wire brush, steel wool, or sandpaper to knock the glaze off works. Hoping when you get there, just for curiosity, you dry some of them off, and try to look for a glossy, glaze look on the plates.

Per your request...

 

[rphillips]

Thanks, All your clutch looks like "I" think it should. For sure it hasn't been abused much at all. Very slight grooves in both inner and outer hubs, plus the "dogs" on the fiber plates show no wear at all, mine were always flattened pretty bad. I don't know why, but I've seen those hub nuts loose several times, You'd think the locking washer, bent up tightly, should hold them, but for some reason sometimes they don't. May want to bend up more sides of that washer. I sure couldn't blame you at all for replacing those old 30K plates, but they sure just don't look, or seem, anywhere near bad enough to cause the problems you've explained. But cable adjusted properly and new springs, I can't think what else could be the culprit. Good luck.

 

[Cipher]

I torn into the 850 yesterday. I took the clutch plates out and measured all of them. I measured thickness at 4 spots on each plate, 12, 3, 6, & 9 oclock.
Spec per the OEM manual for the frictions is 0.106-0.114" with the limit being 0.094", and steels spec is 0.080" with no limit specified.
My clutch plates measured the following:
-The friction plates measured 0.107-0.109", most being 0.107".
-The steels measured 0.075-0.077", most being 0.077".

So my frictions fall within spec, although all are at the low end. All the steels are below spec, but only by ~0.003". None of the steel plates are scored or look worn. Only one plate has 3 areas of discoloration due to heat which you will see pictured below. Also, I dried off the frictions well and gave them a close inspection. They definitely have a shine to them so I think they are glazed. I also noticed that when wiping the oil off them the friction material was flaking pretty heavily and felt somewhat brittle in places. See pictures below.

Here's the only steel plate showing signs of overheating. It's not warped and still has a smooth even surface so I will be reusing it.


Yeah time for new fibres. They look glazed and being a cheap bastard id sand them and maybe shim the springs.
doubt its worth the effort though.

 

[Cipher]

Thanks, All your clutch looks like "I" think it should. For sure it hasn't been abused much at all. Very slight grooves in both inner and outer hubs, plus the "dogs" on the fiber plates show no wear at all, mine were always flattened pretty bad. I don't know why, but I've seen those hub nuts loose several times, You'd think the locking washer, bent up tightly, should hold them, but for some reason sometimes they don't. May want to bend up more sides of that washer. I sure couldn't blame you at all for replacing those old 30K plates, but they sure just don't look, or seem, anywhere near bad enough to cause the problems you've explained. But cable adjusted properly and new springs, I can't think what else could be the culprit. Good luck.

They are glazed and sanding would likely take them past min spec.

 

[rphillips]

For me, clutch plates at, or below, factory spec., does not mean the clutch is already slipping as this one was. The factory spec. tells you it's time to maybe replace so it doesn't start slipping.....Telling you problems are getting near. Kind'f like the factory spec. for brake rotors, they tell you the rotors are nearing the time they may (could) cause a problem. Would be no reason for the min. spec. if the item had already failed when it got to min. spec. Plus they will always give themselves a little wiggle room for safety and for selling more replacements.

 

[93Bandit]

Yeah time for new fibres. They look glazed and being a cheap bastard id sand them and maybe shim the springs.
doubt its worth the effort though.

I agree, probably best to get new frictions. Not only would sanding probably bring them below spec, but I also fear they'll start coming apart. As I mentioned before the material is quite brittle and was coming apart as I clean the plates off. Im a tightwad as well and like to save where I can, but I'll admit I end up going through more frustration and expense trying to save a buck sometimes. Occasionally it's worth spending the money upfront to avoid the hassle and other potential issues.

 

[93Bandit]

For me, clutch plates at, or below, factory spec., does not mean the clutch is already slipping as this one was. The factory spec. tells you it's time to maybe replace so it doesn't start slipping.....Telling you problems are getting near. Kind'f like the factory spec. for brake rotors, they tell you the rotors are nearing the time they may (could) cause a problem. Would be no reason for the min. spec. if the item had already failed when it got to min. spec. Plus they will always give themselves a little wiggle room for safety and for selling more replacements.

I agree with what you're saying. The only caveat with factory specifications is they cannot always capture all possible variables. In this case the measured thickness is within the acceptable range, but what cannot be easily measured is other ways the material has degraded due to time and heat cycles etc. Being the material is glazed, brittle and near the end of acceptable thickness, I think replacement is probably the right course of action. Especially considering I've already addressed all other possible causes of a slipping clutch. This is all there is left to do.

 

[Blue_magician]

How similar are the clutches on the 1978 gs1000 to your clutch? I’m finding two different types of friction plates on mine. I believe it’s the original.

 

[93Bandit]

How similar are the clutches on the 1978 gs1000 to your clutch? I’m finding two different types of friction plates on mine. I believe it’s the original.

I have no idea. I don't have a 1978 GS1000 to compare to.

 

[Cipher]

I agree with what you're saying. The only caveat with factory specifications is they cannot always capture all possible variables. In this case the measured thickness is within the acceptable range, but what cannot be easily measured is other ways the material has degraded due to time and heat cycles etc. Being the material is glazed, brittle and near the end of acceptable thickness, I think replacement is probably the right course of action. Especially considering I've already addressed all other possible causes of a slipping clutch. This is all there is left to do.

Aging of the material might also manifest in shrinkage and compaction. And 40plus years must impact the adhesive.

 

[Cipher]

How similar are the clutches on the 1978 gs1000 to your clutch? I’m finding two different types of friction plates on mine. I believe it’s the original.

21441-49002

is the part number. Fiche shows only one number for all but the latest number supersedes #s 21441-49000

and 21441-49001

which may look different but obviously still fit.

 

[rphillips]

No way to never argue about changing any normal wear items that are 40 yr. old.

 

[93Bandit]

I fitted EBC in 2019, with no trouble. The old plates were ancient and glazed, but had hardly any wear in them. I also fitted three slightly heavier springs and three OEM springs. All is peachy now.

What oil are you using with your EBC clutch? I was reading the Q&A on EBC frictions and they specify NOT to use synthetic oil with the plates unless it is motorcycle specific. I've been using Rotella T4 which I believe is a synthetic blend. Will I be able to continue using this oil with EBC?

 

[Rich82GS750TZ]

Rotella T4 meets JASO MA/MA 2 spec.

​

 

[Grimly]

What oil are you using with your EBC clutch? I was reading the Q&A on EBC frictions and they specify NOT to use synthetic oil with the plates unless it is motorcycle specific. I've been using Rotella T4 which I believe is a synthetic blend. Will I be able to continue using this oil with EBC?

I've been using semi and full synth for the past decade. Mostly car and diesel oil, with only a couple changes using bike-specific oil, when it was priced right.
Currently using Mannol 10w40 car and diesel synth, which has a Jaso MA rating also.