Input shaft/pressure plate contact?

[baffle]

I have asked a question on a UK forum but not found anyone who has seen the symptom my bike has. The bike is a 1980 R65. I have had the bike a few years and always I had a bad change 3rd to 2nd when bike was hot. So I decided to strip bike and while sorting transmission get frame etc blasted and powder coated. This is the first time I have stripped gear box/clutch on this bike. On taking transmission apart, one bearing (input shaft ball bearing) was a little rough but not that bad, and other bearings seemed OK to me. On taking clutch apart, it is clear that the input shaft has been bearing on the pressure plate and worn a recess in it - perhaps 0.1mm deep. Has anyone seen this kind of wear before? thanks
Picture of pressure plate here:

[donbmw]

Can't recall my 80 R65 or my 75 R90 pressure plates looking like that when I had them off.

Don

[Armen]

I usually put a dot of anti-sieze on the end of the pushrod when assembling, but that doesn't do much.
What it looks like is that the clutch pushrod is grinding it's way into the pressure plate. My guess is the bike was run with no clutch freeplay, or the clutch throwout bearing is shot. The pushrod would be running tight against the plate and trying to weld itself to the plate : )
New pushrod, new plate, new throwout bearing assembly.
My guess.
-Armen

[nhmaf]

The earlier, 'heavy' style clutch assembly used a different length pushrod, I think, than the later "carrier" assembly units did (1980+).   I am not 100% sure of this, but there are different part numbers.  Maybe it could be possible that someone fitted  the wrong pushrod or pushrod assembly for the clutch in the bike?
The cut-over date in manufacture would be Sept 1980, I believe.    One can look at the microfiche online in several places, such as MAX BMW here in the states - probably also on motobins.
http://www.maxbmwmotorcycles.com/fiche/DiagramsMain.aspx?vid=51897

OR - perhaps the clutch has been misadjusted at the lever at the back of the transmission (or cable length) so that it doesn't retract all the way/far enough and is dragging  (or the spring in the throwout piston is worn out/compressed)?

I haven't seen this specific problem before either, and my bike is a 1982 with the later style clutch, so I am just offering up possible suggestions to look at.

[Bob_Roller]

I'm not familiar with the first generation bikes pressure plate and clutch assembly, it's very different from the second generation bikes .

The plate that shown, is it the plate that goes up against the flywheel, or is this plate that goes on last after the clutch disc is installed ??

Again I'm not familiar with this setup, but I think the clutch disc may have been installed backwards and the hub of the clutch disc is in contact with the pressure plate .

How does the clutch disc hub surface look, worn and bright ?

[donbmw]

Bob you may be right about the clutch disc. I think I have an old will look when I get home and see if there a difference.

[Barry]

The operating arm on the back of the gearbox should have an external return spring between the gearbox endcover and the arm. Did yours have that spring ?

[baffle]

Thanks for all suggestions.
Clutch was Installed correctly I think - I have the fiche in book form so can check this ok. This is the clutch plate that is separated from flywheel by clutch spring. The external spring was present. The clutch is worn with clear wear ridges on both pressure ring and pressure plate. I could get these faced and get a new clutch plate. It has been suggested that once gearbox is back together and clutch back on I attempt to measure if there is clearance between shaft and clutch (that's gonna be fun!). If no clearance might be crankshaft endfloat prob? But bike wasn't bad before I stripped it - would I know about too much crankshaft endfloat? I had done maybe 7000 miles on her.

[Bob_Roller]

Just thinking out loud here, any chance the transmission you have is a second generation transmission ?

There were differences the first and second generation transmissions, I think the input shafts were one of the main differences .

[donbmw]

Went and found the old clutch disc from my R90. One side is just under size of what the disc material in thickness which would go next to the pressure plate. The other side is 1/4 to 3/8 in hight. I don't think you could bolt the clutch  part back together if the disc was put in backwards. Bob thinking on the input shaft may be the problem I think the newer clutch assy. used and longer input shaft.

[baffle]

Transmission is older style serial Z057199. Push rod has felt ring. Would input shaft from later box fit in old box? Thanks.

[Armen]

Take the clutch disc and compare the OD to the wear pattern on the plate. If the wear pattern shows a larger area than the actual clutch friction disc, then the clutch wasn't centered properly (clutch pilot tool needed) when it was installed. This could have caused the wear pattern you see because the clutch pushrod would be hitting the inner pressure plate off center.
-Armen

[donbmw]

Yes it can. There are 2 shafts depending on the clutch assy the back has. One for bikes up to 9-80 and the other for bikes from 9-80 to 3-85. The bikes made from 3-85 and on have a larger dia. shaft.

[baffle]

Diameter of wear = same as friction disc dia (158mm). Nice idea but think was centred....Am going to find out more about the 2 shafts. Think my bike was registered may 1980. Thanks

[donbmw]

Look for the built date on the data plate. Do you know if the transmission had any work or was replaced.