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Thread: R75/5 clutch question(s)???

  1. #1
    Registered User 10drum's Avatar
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    R75/5 clutch question(s)???

    Greetings, The bike is running good. The previous owner mentioned that the clutch is different when its warmed up quite a bit. I took it for a pretty long ride (for me) yesterday, and noticed the clutch was not smooth, I'd have to let it out extremely slow. At 66K I'm sure that the clutch need some attention. My question is #1; what to look for when taking it apart, and #2 what parts should I replace? Yes, I'll replace the friction plate, should I replace the diaphragm, the compression ring, the release bearing piston? I will buy an alignment tool. Are there other tools I should buy, or are there alternatives I could use? Thanks again for the replies. Phil

  2. #2

    clutch

    Quote Originally Posted by 10drum View Post
    Greetings, The bike is running good. The previous owner mentioned that the clutch is different when its warmed up quite a bit. I took it for a pretty long ride (for me) yesterday, and noticed the clutch was not smooth, I'd have to let it out extremely slow. At 66K I'm sure that the clutch need some attention. My question is #1; what to look for when taking it apart, and #2 what parts should I replace? Yes, I'll replace the friction plate, should I replace the diaphragm, the compression ring, the release bearing piston? I will buy an alignment tool. Are there other tools I should buy, or are there alternatives I could use? Thanks again for the replies. Phil
    check the friction disc thickness at various spots to ensure it's not below minimum AND that it's consistent.
    check spring height
    Contact Southland clutch in San Diego. They do great work resurfacing pressure plates and supplying friction discs, etc. at a substantial savings over buying new. http://www.southlandclutch.com/?gcli...iAAEgLRKvD_BwE

    I've had both my R90s and R75/5 clutches rebuilt by them and couldn't be happier.

  3. #3
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    I just did my clutch on my R100S, I would suggest reading Brook Reams article on his rebuild, nice hints and things to look for. I thought just my clutch was bad which it was. My flywheel was fine but while in there I saw some seepage so a new oil pump cover and seal with bolts, new rear main seal, new shaft boot etc. So there might be more in there than you suspect. Not a difficult job some specialty tools are needed or made, Northwoods Airheads and others have them. Have fun.

    As an added note, I had 139,000 miles on my clutch, no vibrations just could not hard accelerate in 3rd through 5th.
    Last edited by kinterridge; 05-03-2018 at 04:04 PM.
    Dave Hutton '78 R100S (mfg 7/77)

  4. #4
    Registered User ebeeby's Avatar
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    Your clutch wear may very well be well within tolerance. Dry splines are a much more likely issue. Lots of info on the web about pulling the tranny rearward and greasing the splines....
    1973 R75/5

  5. #5
    Liaison 20774's Avatar
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    I agree that the first thing to do is lubricate the input splines on the transmission. Best to pull the transmission to do that...you can also check the health of the input seal.

    At 66K, I would think there's plenty of life in the clutch. I did my clutch at 100K and I could easily have gone farther. But I might drive differently than the PO on your bike. I replaced everything while in there. I figure every 100K is not too bad for a life!!
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  6. #6
    Registered User 10drum's Avatar
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    I checked the clutch actuator. I noticed the the push rod was sticking somewhat. The felt seal is very dry. I am going to lube that up first, to see if that makes a difference before I pull the gear box.

  7. #7
    Registered User ebeeby's Avatar
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    Quote Originally Posted by 10drum View Post
    I checked the clutch actuator. I noticed the the push rod was sticking somewhat. The felt seal is very dry. I am going to lube that up first, to see if that makes a difference before I pull the gear box.
    Examine the whole actuator "train" from the barrel end of the cable of the hand-lever (it should be greased and "pivot, not "hinge) as well as the rear pivot (should be greased). You can pull the thrust bearing and examine as well when you have the rear pivot out of the way to clean/grease. Gear oil should lightly migrate to the thrust bearing to keep it lubed. Last, there is a correct way to adjust the clutch cable and a wrong way. Look up the correct adjustment on the web. And the cables do fail with use and time as the self-lubricating nylon core fails.
    1973 R75/5

  8. #8
    Registered User 10drum's Avatar
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    I ended up pulling clutch. The plate thickness is 5.5mm to 5.6mm. The splines were dry, as was the the finger tips of the diaphragm spring. Probably explains the abrupt clutch action. The Haynes manual said something about "glazing"? I have posted some photos. Im not sure if the plates look right, since this is the first one Ive had apart. On the wet multi plate clutches Ive been into, Id just scuff the surfaces of the metal pates, and the friction plates with sand paper. I'd replace the friction plates if they are too worn. There was quite a bit of clutch plate dust in the housing. No oil to speak of, the dust was pretty dry. I took a photo of the dust, before I cleaned everything up. I'm going to order an alignment tool. Is there anything else I should order? Thanks for the replies. Phil
    Attached Images Attached Images

  9. #9
    Liaison 20774's Avatar
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    That sure looks very dirty/dusty...makes me wonder why that's the case. Here's the in inside of my transmission bell housing after 100K miles. A bit dirty but no where near yours. I don't recall the thickness of my clutch plate, but I remember saying that I could have gone another 20-30K miles easily. I seem to recall that 4.5mm is the minimum thickness??

    TransBefore.jpg
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  10. #10
    Registered User 10drum's Avatar
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    Yeah, I thought it was dirty too, and yes, 4.5 mm is the replace thickness. Does anyone know the thickness of a new friction plate? If this were a car, Id replace the friction plate, pressure plate, throw out bearing, and have the fly wheel turned, just because I have it tore down. But car parts are cheap, and $15 to turn a fly wheel, why not.

  11. #11
    Liaison 20774's Avatar
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    I think 6mm. When I did my clutch, I replaced everything. I figured once every 100K miles is pretty good cost average. If you scrimp on something, you'll be back in there sooner rather than later.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  12. #12
    MOA #24991 Pauls1150's Avatar
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    With that kind of crud buildup (post 8, pic 1), I'd be wondering if the seal has a slow seep...

  13. #13
    Airmarshal-IL James.A's Avatar
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    Another couple of things.... be sure to put a small dollup of grease on the tip of the clutch push rod and be sure to completely clean and lube the throw our bearing disc and related parts there at the back side of the transmission.
    1973 R75/5

  14. #14
    Registered User 10drum's Avatar
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    Quote Originally Posted by Pauls1150 View Post
    With that kind of crud buildup (post 8, pic 1), I'd be wondering if the seal has a slow seep...
    There isn't any indication of leakage, it's mostly just dust. The previous owner had the seal replaced, and if a gorilla mechanic didn't clean things up before he put it back together, that may explain the mess. There was no slippage, just abrupt clutch. The splines and the diaphragm fingers were dry, so I'm gonna lube those up, and see how it does before I spend the $400+ for clutch parts. If that doesn't work, I get to take it apart again. I need the practice anyway.

  15. #15
    Registered User 10drum's Avatar
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    Well, I put it all back together and it worked better, but not as good as I think it should. I really think the plates are glazed, perhaps because of the previous main seal leakage. I replaced everything, and now it is working great. These bikes are a joy to work on, except that effing rubber boot. When they extended the wheelbase, they should've at least increased the gap between the gear box and driveshaft housing about 10mm.

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