I can't seem to completely prevent oil leaks from my M21 primary chaincase.

I suppose I could pull the clutch and improve the oil sealing arrangements as I think that's where the leak is but I wondered if anyone had tried using a spray-on chain lube, as used for drive chain lubrication, instead of an oil bath?

Cheers,
Bernie

email (option): bernie.a.jones@gmail.com

There has been some discussion of this topic on several occasions.

The overall consensus seems to be that if the machine were just used for short hops, and maintained regularly and religiously, then you might get away with a spray-on lube in a dry case....

However, the general wisdom seems to be that for any sort of real riding and especially for long hauls, the chain case environment is too hot and demanding for the chain to rely on the occasional spray for proper lubrication: the factory oil fill level is what is required to keep the chain and sprockets cooled, coated, and alive.

And please don't forget about the rollers supporting the chain wheel/clutch outer hub. These also rely on the primary case oil supply for lubrication, and even though their requirements might be minimal: a spray-on lubricant is not very likely to reach them effectively.

It all comes down to how you plan to use your bike.

email (option): teladelujo@ msn.com

Hi Bernie, My neighbour Bob has run his WD M20 (fitted with B32 engine) with a dry primary for the last 20 years. His trick is to pack the clutch rollers with high temp grease and spray the chain at regular intervals. I assume though, that your bike has the 6 spring clutch, so not sure on how the ball bearings would handle the same lubrication.

email (option): ian@integsci.com

Many thanks for your thoughts on this.

We do the odd long run on charity rides but it's mainly used for fair-weather pootling ('cept when we go up North where it's grim and hook up with the Cheshire boys who only ride out in hailstorms of course - as Ian knows!)

I have the AA clutch fitted so maybe that makes a difference?

Apart from the dry primary idea are there any other recommended mods for improving oil tightness?

Cheers,
Bernie

email (option): bernie.a.jones@gmail.com

Where abouts in Cheshire are you? I'm cheshire born and bred
Dave

email (option): davmax@ntlworld.com

I find the M20 primary drive covers to be well engineered and first prize is to operate as intended by the manufacturer. Having said that, I also have BSA Sloper, build up from various bits and pieces and have not found a primary drive cover for it. I have fitted a home made chain guard attached via three bolts for easy maintenance. The Sloper and M20 make similar power. I have done a number of long trips on the Sloper without problems. The chain guard provides better ventilation and cooling than an enclosed cover. I also use ANSI 40 industrial chain. I carry a spare chain in my tool box, but have never used it.

email (option): pvlietstra@gmail.com

The thing with sealing these chain cases is to understand them.

First of all, they are flexible stampings, not machined surfaces.
As such, when you tighten the center bolt, they will flex in strange ways.
Make sure you have the correct spacers and cork seals in place. Do not overtighten.

So, if you can get them as flat as possible (both surfaces) you will have less trouble.

A good quality sealer such as "Yamabond" will help a great deal also. Make sure you use a non hardening sealer, and one that will release without
jacking things all over the place.

Make sure when you tighten the zillion screws they are tightened evenly. Skip every other one (like you do a car wheel), then go back and get the other ones. Then, do the first set. In a way, it's sort of like tightening head bolts. Sneak up on the final tightening. You do not have to measure torque, but just have it feel even.

I do that, and am pretty much leak free.

Try it and see.

email (option): britool51@hotmail.com