Rectifications involved checking and restoring the condition of: • the outer clutch pulleys, • the inner clutch plates, • the central drive shaft, and • the yoke bearing.
With the transmission apart it was obvious what the problem was – it had been badly gummed up by a lubricant. Someone had applied a generous amount of a molybdenum grease to the square shaft and that had subsequently been flung out and saturated the cork linings. As noted elsewhere in the forum, only dry lubricants should be used in this type of transmission to avoid the inevitable dust and dirt turning the grease into valve grinding paste and from flung grease contaminating the cork linings.
The clutch rubbing surfaces on both outer clutch pulleys were in good condition and so the pulleys only required cleaning.
The inner clutch plates needed a lot of work. I didn’t have spare cork linings and the ones in there had plenty of meat left so I decided to take a punt on cleaning them. Half an hour of rubbing the plates with paper kitchen towels soaked in methylated spirits did a good job of getting a lot of the grease out of the cork linings such that they are now more tan than grey and have the grabbiness you would expect from nearly fresh cork.
The only unknown here is whether the metho affected the adhesive of the cork linings. The cork linings were still tightly glued to their backing but I did notice some delamination around the outer edges, which I fixed with localised injections of solvent based quick grip using the wet bond method. While this was drying the two clutch plates were pressed together using a vice and clamps. Hopefully the glues will still be OK despite the metho and grease – time will tell.
The other matter for the inner clutch plates is wear on bearing surfaces of the square hole through the middle. With all of the old grease removed from both the square holes and square shaft, it was possible to check the quality of the fit of the plates on the shaft. The reverse drive plate (sprocket side) was a close and smooth fit on the shaft, but the forward drive plate had some play and did tend to stick on the shaft, probably responsible for much of the original drive problem. Fine abrasive paper (120 grade) was used carefully to smooth of the square bore of the sticking clutch plate.
The square shaft itself cleaned up nicely. There was one area of corrosion which probably contributed to the plate sticking – a light buffing with the fine abrasive paper was used to take the corrosion back to the surface of the shaft. Use of abrasives was minimised because the last thing I wanted to do was to increase the play between plate and shaft.
The yoke bearing needed little attention, just removal of the excess grease. Because the yoke bearing was OK, smooth and free, I didn’t have to disassemble the yoke bar.
The largest time consumer here was getting the grease out of the cork linings. Without that, cleaning and buffing the components would only take 30 mins or so.
