Dommie oil leak

There is a large lipped oil-seal for the crankshaft drive shaft that has the engine sprocket and possibly the alternator rotor if so equipped. It is a relatively easy job to replace the seal that fits into a machined recess on the crankcase side.

You have to remove:

1)The left footrest and brake lever and chaincase cover

2) Fit back the brake lever so you can hold the rear wheel from turning after you have selected top (4th) gear and undo the big nut on the engine sprocket shaft then remove the brake and primary chain.

3) You then need to remove the engine sprocket.... This unfortunately is often extremely tight or stuck on. Whatever though, you need a strong sprocket puller to pull it off. Often a sharp tap with a hammer on the centre bolt after the puller is tightened hard will release the sprocket, but remember not to hammer tooheavily as you are hitting the end of the crankshaft and you don't want to damage or distort it.

3) You will then see the large gator-type seal which can be prised out by spiking it and levering it out carefully bit by bit all the way round the circumference.

4) Carefully reinstall a new seal (metal side outwards) but take care, it is easy for the seal to start to go in cocked over...it needs to go in steadily and squarely so tap in gently with a large box-spanner or tube so it lies flush with the crankcase metal.

Rebuild is a reverse of the strip down making sure you have the nut tightened strongly and the chain's split-link in the right way round with closed end forwards when on the top chain run.

Les

The engine sprocket can be very hard on its taper, Don't buy a puller designed for a commando,it wont fit. You may have to borrow a NORTON puller from another enthusiast. Some make do with Automotive pullers but they usually dont give a straight pull as they can't get between the sprocket teeth, Dont lose the woodruff key which will have to be levered out with a small screwdriver.

Just a tip: Before using your chosen puller, buy a large diameter suitable size "Jubilee" clip to wrap around the three legs. By tightening this clip up (yes it will distort to a triangle shape rather than round) this will help stop the legs spreading out and coming off the back of the sprocket

Les

Depending upon how long since it (the engine sprocket) was last disturbed, sometimes the: 'judicious application of heat may be beneficial', i.e: a blowlamp.