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Old 08-10-2013, 03:02 AM   #1
Dakalberry OP
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1978 r80/7 cafe racer project - clutch rebuild advice needed

Hi guys

I'm in the process of rebuilding a basket case 78’ R80/7 cafe racer. It wasn't running when I got it so I've never actually had an opportunity to ride and test it. As result I don’t know anything about the condition of the clutch other than what I can see when disassembled.

I was hoping for your opinion about whether I need to replace all my clutch components, some of my components or if I can hopefully get away with what I already have. On a piece by piece basis I have the following:

Diaphragm Spring - (PN: 1234035 – so the HD version) with a thickness of 2.8mm and relaxed spring height of 17.5mm – so both within spec. All of the fingers look to be in great even condition with no excessive wear evident.
[IMG][/IMG]

Friction Plate - Sachs PN: 1864 374 033 (BMW PN: 21 21 1 236 332) with an average plate thickness of 5.93mm. Overall the plate looks to be in great condition with no rivets showing, deformation or oil stains etc.
[IMG][/IMG]

Neither the pressure plate or the compression ring have a part number. Both these have a mottled/spotty appearance with what appears to be heat spotting however there is NO cracking or crazing of the friction surfaces.



Obviously these parts are my greatest concern, so are they in need of immediate replacement or is this something commonly seen in Airheads??? If I replace just these two parts, is there any issue running with the existing clutch plate and diaphragm spring?

What would you guys do?

I’m in Sydney Australia and am not aware of an Aussie based airhead clutch reconditioning service like that offered by Southland Clutch in the US but please correct me if I’m wrong.

Bear in mind that this project is running on a shoestring budget and I don’t have cash to burn but I do want it to be right…

Any advice/guidance is greatly appreciated!

Charlie
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Old 08-11-2013, 06:26 AM   #2
chollo9
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Clean up the pressure plate with some brake cleaner and a fine Scotchbrite pad or steel wool and put it all back together. It's within spec and looks good, so run it.
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Old 08-11-2013, 03:34 PM   #3
Dakalberry OP
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Thanks for the reply and advice, I really appreciate it.

Out of curiosity, what are the black spots on the pressure plate and compression ring? Are they a sign of problems down the track or just a normal occurrence for these clutches? I did read that they may indicate/cause clutch chatter, does that sound plausible?
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Old 08-11-2013, 04:03 PM   #4
disston
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+1 what Chollo said.
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Old 08-11-2013, 04:33 PM   #5
Kai Ju
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Clean up

A word of caution when you clean the clutch. Make sure there is no residue left when you're done.
I cleaned my clutch when I installed my light flywheel and the clutch slipped big time on my first testride.
Since the existing clutch was well within spec and not contaminated with oil, I just babied it for a while. So no hot rod take offs or full throttle acceleration in higher gears.
Well, it came back to full strength in less than 50-100 miles.
All I can figure is that there was stuff left on the plates that had to either completely evaporate or burn off.

So, if it slips, taken it easy and you'll probably be ok.
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Old 08-11-2013, 05:18 PM   #6
disston
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It is often suggested to ruff the surface with a coarse sandpaper. 80 or 100 grit. Do both pressure plates. This will not change the depth or thickness any but help grab the clutch disk.

Maybe others don't do this? I always do.
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Old 08-11-2013, 05:44 PM   #7
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Deglazing the pressure plates is a good thing. I generally use finer paper though - around 320. Doesn't much matter as long as you rough it up some and take the shine off.
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Old 08-11-2013, 10:34 PM   #8
bmweuro
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You can try roughing up the plates but with all of those hot spots a new disc will chatter for quite a while.
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Old 08-12-2013, 03:12 AM   #9
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I've re-installed used but good clutch parts a bunch of times on my /5, and the only time I had trouble was when I over-lubed the splines. I figure that the only thing I lose if it goes bad is the two hours or so that it takes me to do the job.I don't think I'd be as willing to do so on my Guzzi, as changing out the clutch on it is a much bigger job. Like everyone else says, just sand everything up before putting it back together.
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Old 08-12-2013, 06:35 PM   #10
kixtand
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Quote:
Originally Posted by bmweuro View Post
You can try roughing up the plates but with all of those hot spots a new disc will chatter for quite a while.
My thinking as well...
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Old 08-12-2013, 08:58 PM   #11
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Hi everyone

Thanks very much for the replies and advice, I really appreciate it. I’ve given all the parts (except for the clutch plate) a thorough degreasing and good scrub with a Scotch-Brite before concentrating on the pressure plate and pressure ring friction surfaces with some 320-grit wet and dry. I finished off by giving everything (clutch plate included) a very liberal spray/clean with CRC BraKleen. End result below along with the lightened flywheel I scored on eBay.

The possibility of clutch chatter as noted above is in the back of my mind but as mentioned it is not the end of the world or that big a job to do down the track if it does become an issue – fingers crossed it wont be required.

Thanks again

Charlie

[IMG][/IMG]
[IMG][/IMG]
[IMG][/IMG]
[IMG][/IMG]
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Old 08-13-2013, 12:48 AM   #12
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Picture of lightened flywheel?
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Old 08-13-2013, 03:44 AM   #13
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Hi disston

Iím away from home now for 10 days and all I have are these shots from when I purchased it.

You can see the variance in weight between the stock unit and the modified.

$150 on eBay and the seller had zero information about who did it, he bought it that way but never put it into use. Iíve still kept the original just in case itís too light and I donít like it (i.e. the motor not being as smooth as it should be).

Charlie

[IMG][/IMG]
[IMG][/IMG]

[IMG][/IMG]
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Old 08-13-2013, 09:00 AM   #14
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I see in one picture the F mark is retained but looks like no OT or S mark? I guess you can live with that. Maybe use a chop stick in a plug hole when you want to set the valves.

On second glance I notice the marks added for OT and S.
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