Anyone who goes out to the garage in the morning and isn't greeted by the smell of thick old oil seeping through felt is missing out on one of the great sensory pleasures of owning an English motorcycle.

The greatest argument against experimenting with gearbox lubrication is that sudden and catastrophic gearbox failure is just that...catastrophic. It doesn't matter how quick the rider's reactions, pulling in the clutch doesn't help with a gearbox seizure and it's not the 'Technical Lead' who has his life on the line. It's most unlikely that their product has been tested in a BSA transmission.

Underfilling an M20 box on the grounds that "filling a gearbox to capacity with grease invites trouble" is probably not a good idea. As I understand it, the M20 box is effectively a V-twin transmission turned on it's side in order to make it fit and unlike the majority of similar countershaft boxes, it does not have the benefit of a layshaft at the lowest point which will deliver oil to the other parts even when the level is low.

Bikes such as Ian's and Ron's are witness to the fact that with a sealed sleeve gear bearing, careful assembly and a preference for the rear rather than field stand, these boxes don't have to deposit a puddle underneath at every stop.

To be honest I am dubious about the ability of grease to correctly lubricate a gearbox designed to carry oil...

Trevors comments on why grease is being used ref. leaks and relative size of 'internal' and 'external' clearances of the box are a valid observation and entirely logical...

Nevertheless, I'm not against experimentation, I have done it myself numerous times with modifications and clearance alterations...

If nothing is ever tried nothing is discovered...I'm with Maarten on this one..Let's see how the experiment goes over time...That's the ultimate test...Ian

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

Yes, I agree with Maarten and Ian on this. It is a generous offer by Dave to test the 'grease issue' on behalf of all us forum members who have, over the years, pondered on the subject. It is all going to be down to whether the spec of this grease is different enough to the basic types we put in our grease guns to do the job. I think the verdict on 'standard thin stuff' is already known, so lets not be too hard on a guy who is willing to field test an alternative for us. Duncan

I have a stuffed gear box.
I have clearences for the oil slingers on RR V 8's .
Right up to the end of the 6.75L V8 it had a slinger front & back on the crank.
Allowable clearence was around 0.002" and std was .0005" to .001".

Is that what you are looking for ?
I put 000 gear grease into my box on the advice from some well respected vintage bike owners.
The box ran for about 5,000 miles before I started to get some changing problems which I should had addressed.
It had brand new layshaft bushes put in along with a new countershaft bush.
The layshaft was blued on the end when I took it out, so it was running very hot.
The feed hole for the far end of the layshft was blocked with dried up grease so it had been sitting there & not wicking in like oil is supposed to do.

I am a mower mechanic ( currently ) and pull down a lot of mower, tiller & auger boxes that run in grease. The passage ways for grease to pass through are substantially bigger.

Liquid grease is designed to be pumped into bearings under pressure, not flow under gravity ( that comes from the grease manufacturers ) which is why you buy it in 20lb tubs.

Now if some one wants to try it, they are welcome.
I have done my bit the are free to ponder what I have said or ignore it.

A flatmate rebuilt his box into a set of NOS cases.
His did not leak mine did.
His was full of oil & mine was full of grease

email (option): bsansw1@tpg.com.au

No kidding about the leaks. Mine pours out oil just sitting there. I find the bike doesn't shift as comfortably as it should unless the oil is full up and if it's full, it leaks bad. I can't imagine how they operated like this given how oil was an important war commodity, what else did it get wasted with?

email (option): paulscutler@gmail.com

They didn't leak much when new, that was the whole point to the previous postings.
Get a NOS outer gearbox cover and have a look at how much smaller the holes are.
Ditto on the shell.
Just like air through a radiator with and without a shroud, there is a limit to how big the gap between the scroll & the case can get before the viscous friction within the oil being pumped back in can not bridge the gap between the scroll & the case.
If your box won't change unless it is full pull it out and have a good look at the layshaft shift forks and the timing side layshaft bush.
Better than average chance the bush is oval so the forks have been rubbing on the ends and gone through the case hardening

email (option): bsansw1@tpg.com.au