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Subversive
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Discussion Starter · #1 · (Edited)
Hey folks,

Just got a new clutch (plates) installed on my bike, a 1981 CB900C..

Never experienced this before... During slow engagement of the clutch, as in when trying to do a nice gentle take off from a light with a slow release.. There is a clear and definite pulse, as in intermittent engagement, similar to brake pulse caused from a warped rotor...or an out of balance washing machine on the spin cycle.. Once fully engaged the clutch seems fine but during gradual engagement there is a clear partial engagement that is cyclic and not helpful for adding steady power in situations that call for clutch slipping..

Any ideas what might have gone wrong with this install or ideas in general?

Thanks
 

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Retired twice: Navy and as a govt contractor
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Did you soak the plates prior to installation? Are the plates in the correct order and orientation? Is there a spacer plate?
 

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Subversive
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Discussion Starter · #3 ·
Did you soak the plates prior to installation? Are the plates in the correct order and orientation? Is there a spacer plate?
I was thinking about the soak... I really don't know because I didn't do it... I'm just trying to get an idea what might be going on...

I called the guy up and he tried to sell me on the idea that clutches waaaaay back in 1981 were "different" and might act like that... I told him (BS)... But he may not have understood what I meant when trying to explain over the phone...

I am bringing it back next week but I am concerned about using the bike in this condition... I try very hard to take care of this old girl...

I can't believe they couldn't get something like a clutch right... :confused:
 

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Way back in 81.

I just happen to remember riding bikes way back in 81, in fact I still ride a 1979 XS11 on a regular basis. I can assure you clutches did not pulse back then. They should be smooth.
There is a different pressure feel on the lever, from a cable to an hydraulic clutch.

For pulsing and other strange behaviour, you have to go British 3 spring cork clutches from the sixties.

Unkle Crusty*
 

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Subversive
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Discussion Starter · #5 ·
I know I rode a bike back in the 70s as a kid and the...oh this is just silly..

What are these people thinking? I don't know if this was an honest mistake or just a communication problem.. Seems like everyone is so Full Of $hit these days... I have given the guy hundreds of $$ of work and planned to have him do more work and this is the response I get? Holy %$%$!#$^!

I just don't want to damage anything in the meantime like the new plates, which btw ARE cork..
 

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Since the clutch isn't working right, it should be returned to the shop. That's definitely not normal and something they should have felt right away when test riding. My guess is that something is warping the plates to some extent. They need to be very flat in the basket.
 

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Were only the fiber plates replaced? It's proper to replace the entire pack, fiber and metal. Also, what is the condition of the clutch basket? "Divots" can form in it that will hamper the smooth movement of the plates.
 

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Subversive
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Discussion Starter · #8 ·
Were only the fiber plates replaced? It's proper to replace the entire pack, fiber and metal. Also, what is the condition of the clutch basket? "Divots" can form in it that will hamper the smooth movement of the plates.
He said the basket was fine and if the metal plates needed replacement then I wish they would just sell them together.. The clutch was not doing this pulsing before, just slipping...

I am concerned that when I get the bike back there that he'll test it out and say, no, no it's fine.... Then it's on to the next mechanic.... Ugh...
 

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So I'll take that as a no on the metal plates. The new fibers will allow the (most likely) heat damaged metal plates to show themselves. There was no symptom before because of the worn fiber plates inability to effectively "grab". When you initially inquired about the job, did the parts people ask if you wanted both fiber and metal? Were you given a total price and decided against the additional expense? Did you buy an aftermarket clutch "kit" with the thinking that it would be all inclusive?
 

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Subversive
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Discussion Starter · #10 · (Edited)
So I'll take that as a no on the metal plates. The new fibers will allow the (most likely) heat damaged metal plates to show themselves. There was no symptom before because of the worn fiber plates inability to effectively "grab". When you initially inquired about the job, did the parts people ask if you wanted both fiber and metal? Were you given a total price and decided against the additional expense? Did you buy an aftermarket clutch "kit" with the thinking that it would be all inclusive?
Well since the plates spin I would have thought that even imperfections would be uniform in a circular pattern and thus not cause an "out of balance" situation where at 2 o'clock it starts to grab but at 8 o'clock it doesn't -- this is what is happening but it didn't do that before, it was smooth before. It seems to be fading now though and if it goes away too much he'll just say, oh it's fine...I bet.

As far as my choices, I asked him what to get.. He likes ME to get the parts... I guess this helps him keep the price down... If, as you say both the metal and the fiber should always be replaced then it would be nice if they sold them together.... I just looked around for what people suggested as a good brand and got the fiber plates that he asked for. (EBC cork)

What happened tells me a lot about what they are doing and part of that is clearly not checking the work.
 

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Unfortunately, wear and/or damage never follows a uniform pattern. This is most visible when you see a tire at the end of its time. while the tire has no bad "feel", it still has areas that are worn slightly further along than the rest of the circumference. As someone who worked parts for quite a while, I think they did you a disservice in not emphasizing the importance of replacing both sets in a 34 year old motorcycle.
 

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I always replace the disks and plates just to be sure. The parts are fairly inexpensive and it doesn't take much deflection of the plates to mess things up.
 

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Subversive
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Discussion Starter · #13 ·
Unfortunately, wear and/or damage never follows a uniform pattern. This is most visible when you see a tire at the end of its time. while the tire has no bad "feel", it still has areas that are worn slightly further along than the rest of the circumference. As someone who worked parts for quite a while, I think they did you a disservice in not emphasizing the importance of replacing both sets in a 34 year old motorcycle.
Yes, I agree. I ask him normally, this time I asked if anything else should be replaced, like the springs...because I had read that they should be replaced.. I didn't think of the rings although now it seems obvious..

He normally just poo poos the idea when I suggest such a thing... I feel like for some reason the mechanics I have dealt with don't like my bike or don't like old metrics or something.. If it was a 1981 HD then I feel like it would be a different story... I don't know what's up with that.. I'm going to talk to him about this but if he plays stupid again I am going to try to find someone else, and that's not easy because there are so few good mechanics who are also trustworthy and knowledgeable.
 

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Subversive
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Discussion Starter · #14 · (Edited)
I always replace the disks and plates just to be sure. The parts are fairly inexpensive and it doesn't take much deflection of the plates to mess things up.
It makes sense I'll make sure next time...

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So given what has happened what is a likely fix, to get new rings? Or will it need all new parts now?

Thanks
 

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New mechanic.

You have me thinking about a long time ago. I had a mechanic put my 650 BSA engine together, and he missed a couple of important details. That resulted in a knocking big end bearing.
I went to another mechanic for the second rebuilt, and that made all the difference.

Unkle Crusty*
 

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So given what has happened what is a likely fix, to get new rings? Or will it need all new parts now?
I bet the new clutch disks are still in good shape. A set of plates will probably fix things right up.

It's important that everything gets put together in the right order as well. It might be a good idea to double-check that.
 
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