Hi All I had a huge oil leak around primary chain case area , found out it was the inner chain case to gearbox, it had a rubber gasket plus the chain case flange was distorted, this is a tricky one because the gearbox has to move to adjust the primary chain, was thinking about a cork gasket (or do they use a felt gasket ?) )c/w thin reinforcing strips around the screws to stop the distorting, but I think that might interfere with the clutch release, anybody done this type of repair lately? Regards Barry
Hi Barry You are right there is a cork gasket between the gearbox and the inner primary,the original one was of a rubber impregnated cork that is about 1/16 thick,the thin plates are used to lock the bolts that are tightened up till they bottom on their shoulder, this puts the right tension (squeeze) on the gasket to seal against oil leaks but still allow the gearbox to move for chain adjustment,smear the back of the primary and the gearbox face with thick grease to allow the box to move easier.The gasket between the inner and outer primary cases is 1/8 cork,this can be sealed with non or semi curing gasket cement.I made this gasket from 1/8 silicone rubber sheet which worked very well.There is also a felt washer that goes into the circular track in the outer chain case,I usually glue this in with contact cement then soak with thick oil,also at one time there was a rubber lip seal available to replace this felt washer it worked quite well in sealing against leaks.There will usually be a bit of a drip out of this seal when the bike is parked.If the outer primary hold down screws are tightened too much the movement of clutch pressure plate will be restricted by the felt ring and the clutch won't completely free off. When all is correct the outer primary shouldn't move when the clutch lever is pulled in fully at the handle bar.If the primary cases are pulled too close together the outer will show movement around the sprocket as the clutch lever is pulled in and out at the bar.If you have things as far apart that you can change the inner cork gasket at the gearbox face ,you should be checking the condition of the throw out bearing thrust washers they should show no signs of tracking and should be flat,also you need to check the length of the three rollers that run against the face of the spring carrier and that the face of the spring carrier is not all galled by the 3 rollers.All this to say that if the all the parts aren't in good shape the clutch will be a real SOB to adjust and to work reliably.
#630533 - 12/17/156:20 pmRe: Sealing the inner primary chaincase to the gearbox
Joined: Oct 2015 Posts: 47barry2
BritBike Forum member
Hi Jonnie Thanks for that, the rubber gasket is a "bought" one and looks in good condition, so may use again, can't see why it got distorted on account they cant be over tightened unless the outer chain case was pulling it all the best Barry