Any reason why you can't run an M20 without oil in the primary chaincover, but use sytnthetic chain lube on the primary chain. (less messy?)

email (option): jeff@infinitymedspa.com

This has been a point of contention and much debate in previous postings. I currently run an o-ring chain in my primary with no issues. I do - for my own peace of mind -- occasionally hit the chain with some Amzoil Metal Protectant. An excellent chain lube. Once it sets up - it doesn't come off. I also use it to recoat all my hard to find and usually quite expensive vintage parts. No - I don't own any stock in the company. How's everybody?? Haven't posted for a while.

Jeff,
The clutch bearing relies on the oil that's being sprayed around the chaincase for lubrication and the oil goes some way to cooling the chain.

Well I'm ok Frank
Jeff unless you run an o ring chain like Frank and unless you only use the bike for short hops, it's best to put oil in the chain case as the manufacturers intended. The primary chain is wizzing round at something like three times the speed of the rear chain....and it's in a hot environment. Ron

email (option): ronpier@talk21.com

I have not found this to be a successful method of lubricating the primary on a long run..largely because of heat build up and the consequent melting of the lubricant. I comprehensively trashed a chain in one 400 mile run. For short duration runs I would think it would be
an option..but as Matt points out there is the question of clutch roller lubrication to consider as well...Ian

email (option): ian@wright52.plus.com

I have had to ponder this issue myself for my M20/Indian special. I wont be able to make the chaincase oil tight. So I intend to make it more open to air flow at the back. Run an o ring chain and grease the clutch rollers on assembly. Then just squirt some oil around at intervals. If something gives out, i'll have to re-think things Ron

email (option): ronpier@talk21.com

The two potential problems are heat and lubricant ejection. Test on modern bikes (i.e., more powerful and higher-revving than an M20) done with a primary chain which is initially well-lubricated show that, because of the high angular momentum at the crankshaft sprocket which is much higher than any of the other sprockets, lubricant is almost immediately ejected and the chain dries up almost immediately with catastrophic results. Just as importantly, the same tests show that even if run in a completely open primary (i.e., lots of air to cool the chain) the combined heat and lack of lubrication consume about 2 bhp of the engine's power as compared to a fully lubricated, oil-bathed primary chain so even if the chain does not break, you'll be giving up some power - not that M20s don't have plenty of power to begin with! I do not know whether these tests were conducted with O-ring chains but I suspect that some loss of power will result even if less than the 2 bhp. If you chose to test this, please let us know of the results.

email (option): jonny.rudge@verizon.net

My 'test' with a conventional Renolds primary chain ended with a lot of broken up chain rollers in the bottom of the chaincase after a run of approx. 400 miles at 60-65mph (on my 1951 rigid B33).
I was grateful I completed the run without the chain actually breaking, as in the latter stages the noise from the primary drive was alarming!
So as far as I am concerned long runs with this set up are a non starter.
As far as lubrication of the clutch rollers are concerned it should be remembered they are not running all the time but only when the clutch is disengaged, so they do have an easier time and some type of high temperature grease might do the job..
When I built my B30 I converted the clutch rollers to a sealed bearing, which involved some head scratching and machining work but not only does this remove the need for external lubrication but it also eliminates 'rock' in the clutch sprocket and loss of lift when the clutch is pulled in.
That might be a worthwhile alteration to look at if you are seriously contemplating running without oil.
The 'O' ring type chains will no doubt survive better than conventional ones but there is still the question of heat build up and what effect that will have and the lubrication (or not) of the sprocket teeth to consider.
On balance I think some effort invested in stopping the cases leaking might be more productive.
After all it is oil leaks from the cases that is the actual problem...Ian

email (option): ian@wright52.plus.com

Hi,
clutch roller, sprockets and between cush drive and sleeve -all need lubrication and cooling.

I do not think spray can really do the job..
There is, however a "Trick" I learned from an old BSA mechanic:
If you can bring your primary case to a fairly sealed condition, you can mix grease and tick oil together,
to get some kind of a "mix" which is somewhere between oil and grease, so it does not leak out,
and still supply at least some oiling, cooling and damping the noise which is boosted by an empty primary case.

I got my case fairly sealed, so I use some "Anti smoke" oil, which is a honey-like very tick oil.
Of course, if using thick oil/grease, I guess it would be good to combine with o-ring chain, as the tick oil would not penetrate Very well between a regular chain links.

Noam.

email (option): noam10@gmail.com

This question comes up on every forum.You definitely can't run the chain without constant oiling in the primary. Do so at the risk of broken chain and smashed primary. If the factory made it that way, it had a reason.

Actually, the other way, Noam. The o-rings are designed to impede the exit of lubriant from inside the rollers. Therefore they would also impede the entry of lubricant. With any kind of lubricant bath you'd be better off with regular chain than one that has any sort of provision for retaining lubrication.

email (option): jonny.rudge@verizon.net

On my B33 I fixed the gearbox in place and machined an aluminium plate to replace the sliding plate behind the clutch. This was screwed to the back of the casing once positioned correctly and sealed with silicone. The plate was fitted with the mainshaft oilseal from a T140 Bonneville, which is the same diameter as the BSA mainshaft.
I then fitted a modified chain tensioner from a BSA A65 to take care of primary chain adjustment. This required a mod to locally strengthen the back of the inner case to take the tensioner pivot spindle.
Careful fettling of the primary chain cases to produce a flat surface ensured the best possible seal for the gasket, which I sealed with silicone. I also blocked the 'vent' in the back of the inner primary chaincase figuring this wasn't really necessary.
Footrest bar spacers were replaced with more solid machined versions improving the seating over the standard type and I replaced the cork sealing rings with rubber ones..these were also sealed with silicone jointing compound. Finally, I replaced the inspection cover fibre washer with an 'O' ring.
That lot pretty much solved the problem of leaks...Ian

email (option): ian@wright52.plus.com

i found on the B31 i have the primary chain case foot peg inner space was replaced by 2 hydrulic cylinder dust covers with a strong spring in between it was working ok