Clutch Adjustment
The clutch lever should have 4 to 5 mm of free travel.
The adjustment is obtained by means of the adjuster provided at the lever.
When no further adjustment is possible in this way, remove the engine right side cover, release the locknut and turn the adjusting screw fitted to the clutch operating lever pivot. The distance between the lever and crankcase should be 15mm. This is of utmost importance. After adjustment tighten the locknut and replace the side cover. Then use the adjuster on the hand lever to obtain the correct free travel.
Periodically check that the clutch operating lever does not contact the crankcase when the handlebar lever is fully depressed.
The operating lever wears at the point it bears on the pushrod, usually because insufficient freeplay
has been left. The lever can be reclaimed with a small blob of weld, filed flat.
It is important to have a good cable, the Venhill 'Featherlite' cables are reccommended.
Cable routing is important especially on Sports, try not to have tight bends especially around the headstock.
The 350s and 500s use a dry clutch so there is no oil to flush out the debris. They do need to be cleaned from time to time. If there is oil in the clutch the oil seals have probably failed and should be replaced.
Check that all the plates (bar one) are flat and not buckled. You will find one concave plate, this is
supposed to give the clutch progression rather like a diaphragm clutch. This is usually the last metal plate so that when viewed
from the outside you are looking into the dish. In time this plate will tend to flatten out.
Check for wear on the splines and tangs of the clutch basket, any burrs can be removed with a small file- but not too much
as this can make the clutch chatter.
The springs should all be checked for length, and ideally should be the same length.
If, having made the above adjustments, the clutch is not silky smooth, it needs to be shimmed.
By shimming you remove the backlash between the clutch outer drum and the clutch centre, that causes the clutch to bite and then release, bite then release as the clutch rides in and out on the helical cut gear.
To check if you need to shim the clutch.
Remove all the plates, grasp the clutch outer drum and attempt to move it in and out.
If it moves it needs shimming.
If it rocks from side to side then the bush it runs on is worn out.
If you can measure the in and out play using a dial gauge then it will help in the shimming.
How to shim your clutch (originally written by Benjy Straw of WeeVee)
1. Remove cluch centre
2. Locate hardened steel washer. Not to be confused with the large thrust washer which should be nylon or bronze.
3. Measure its thickness, it will probably be .8mm to 1mm thick.
You will need to reduce the thickness of this by a bit less than
the end play measured. The best thing will be to get a stack of shims (e.g old BSA crank shims or similar) and build up.
4. Fit shims and refit centre.
5. The clutch centre should turn freely, when using the kickstarter.
The idea is to remove nearly all the end float but leave enough
for free running.
6. Reinstall plates, pushrod, outer plate, springs and nuts.
This is a time consuming process but well worth it.