Hi,

Today I decided to fire up my M20 and run her up (she last ran on the show circuit last summer) And have swapped petrol tanks and levers ect since then so not had the opertinity to fire her up since.

Whilst first parading her I noticed that the engine oil level has dropped considerably, but more worryingly, my gear box is bone dry ... Again ???

When I purchased her last year I found the gear box bone dry, so I added a pint of oil (as per lubrication chart) and since then she probably traveled a total of 5 miles last year on the show circuit, and this afternoon the gear box is bone dry


I gently pushed a long black Zip tie right down into the gear box and when I drew the zip tie out, there was'nt a single bead of oil on it !!!

Apart from the usual small patch of oil (Where BSA's mark their territory) there is no large leak on my garage floor.... However my new bash plate is rather oily on the top service !

Has anyone had this problem before ? Does anyone know where my Oil had gone ??





Kind regards,

Mark

Ps .... I couldn't get her to fire up either ! Don't know if that has anything to do with it ?

email (option): towersmark84@yahoo.co.uk

Well if it wouldn't start after a long lay up and your oil tank is low? It's probably 'wet sumped'. The oil has drained down to the crank case. There should be a hole in your sump plate to allow you to remove the drain plug with a socket. Drain the crankcase (into a clean container if you intend to reuse it)

Your gearbox oil will usually leak through the mainshaft bearing and onto the floor. It's a good reason to fit a sealed bearing if you do a gearbox rebuild.

Also it's possible for some engine and gearbox oil to enter the chaincase, so best remove the level plug to check. Ron

email (option): ronpier@talk21.com

Thank you Ron !

I will look at the points you have raised and also look at fitting a sealed bearing !

Many thanks 👍🏻

Mark

email (option): towersmark84@yahoo.co.uk

Has it been kept on the propstand since last run?
there's your answer, it'll be inthe chaincase.

so your bearing seal is dud/wrong/missing/wrongly fitted?

Good evening Ken,

Yes ! ... She's been on her propstand ever since the show season last summer !

Is this a common fault?

I will drain the chain case first thing tomorrow !land investigate! I had to down tools and walk away today !

Thanks very much for your reply !

Cheers,

Mark

email (option): towersmark84@yahoo.co.uk

There isn't an effective seal at the drive end of the WD gearbox and leaving the bike on the field stand will speed up the loss of oil...

With a standard gearbox, under normal running conditions I recommend that the gearbox oil level is checked and replenished every 300-350 miles to avoid premature wear of the sleeve gear bushes (they go first usually)...

The common 'fix' to improve this situation is a sealed drive end bearing...I generally remove the inner seal when fitting...The number for this bearing is 6207 2RS, the 2RS indicating two rubber seals...

It's a metric bearing and thus readily available from bearing suppliers...Go for a 'branded' make (Japanese or European), not the cheapest you can get...

I can also supply them if you just want to buy both bearings for the box...

Think carefully before stripping the gearbox...This is one of the more challenging jobs on the M20 and you will have to absorb and understand all the available relevant information (lots here on the forum) and have the tools and facilities to have any chance of a successful outcome....Ian

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

"Is this a common fault?"

yes
applies to all our sort of bike

Yep, all early (pre war) Triumphs suffer from this as well - again a sealed bearing is a solution.

Its funny really, if you lean the bike to left (on prop stand) the oil leaks out the sprocket side.
If you lean the bike to the right - it leaks out of kick-start (Nortons) and/or the gear-change (Triumphs).

Together with leather and felt seals, its probably one reason, early gearbox's sometime use grease ..... which still leaks out when hot ......

Lip seals didn't come into common use until the late 40s/early 50s..In the case of BSA they were reasonably quick off the mark having fitted one to the B/M Series heavyweight box in the very early 50s...

Until then felt and leather was pretty much all they had available..Ian

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

When you look at the design it is no surpise the box looses a lot of oil as the oil level is much higher than the hole in the casing for the mainshaft/sleeve gear. Theoretically it will loose, just with standing horizontally, about 1/3 off its contents over time.

I just noticed that the early '30 boxes, from which the WDM20 originates, had a pattern change on the filler neck to increase the oil level by approx. 20 mm.:



The WD box has the filler neck on the same height as this "changed" box.

So it looks like the BSA designers had a hard time and were forced to increase the oil-level and take the leaking for granted....???

Cheers, Michiel

It is all about design as the Sloper box is much better at this point, with its mainshaft placed vertically above the layshaft, so high in the box with an oil-level way below the large ball bearing.



But this is a handchange box. I guess that BSA decided to go the easy way to turn this box 90 degrees for making the footchange option available but sadly created the oil level problem with it....

Cheers, Michiel

I had heard that these pre war boxes can suffer from a lack of oil? Ron

email (option): ronpier@talk21.com

Hi Ron, If you mean the "horizontal" boxes they probably will have the same oil-level problem as the WD boxes, as they share (apart from some details) the same shell.

A typical problem which I relate to a low oil level is that the bronze bush besides the large ball bearing is often worn out, mostly together with worn teeth on the sleeve gear and the corresponding one on the double gear.

This set of gears are the first to wear because they are under power in all gears except top gear, but I guess a low oil level speeds things up. Think the bronze bush will go first because of the lack of oil, this brings the layshaft further from the mainshaft, the teeth are now not meshing in the correct way and wear out also.

Think this also causes the sometimes quite loud "howling" of the gearbox when in 3th gear.

Cheers, Michiel

Michiel W

When you look at the design it is no surpise the box looses a lot of oil as the oil level is much higher than the hole in the casing for the mainshaft/sleeve gear. Theoretically it will loose, just with standing horizontally, about 1/3 off its contents over time.

I just noticed that the early '30 boxes, from which the WDM20 originates, had a pattern change on the filler neck to increase the oil level by approx. 20 mm.:



The WD box has the filler neck on the same height as this "changed" box.

So it looks like the BSA designers had a hard time and were forced to increase the oil-level and take the leaking for granted....???

Cheers, Michiel

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

As per other comments, a gearbox strip and replace the main output bearing with a sealed one will cure your problem. You'll still lose a little bit of oil along the way, but nowhere near as quickly. I did this job on my M20 last year. If you haven't had the box out and apart before then it's worth taking time over the job as you may find other things that need attention or break, at least that was my experience. Make sure you get the tools you need also, the essential is the puller and also if you have the single spring clutch the compressor. I got on ok with C spanners for the various nuts on the primary and final drive, but Rob does other tools for these - in my case they needed some fettling to match the associated nuts.

I've several pictures which I can put up later in case you want to see what the job is like.

email (option): dickie.bobbie@hotmail.co.uk

email (option): ronpier@talk21.com

Hi, i had this problem,too. I always use only a side stand. I have changed to sealed bearing, but after a few weeks it was leaking again. Now i use a mix of gearbox oil and gearbox grease . that gives the best effect, i think. its ok now for a few thousand miles...greetings jarek

email (option): jarek@jareksgarage.de

Hi Jarek,

That's great to know ! Thanks for finding time to add a post to my query !

"Intelligence gives strength to the arm"

Kind regards,

Mark

email (option): towersmark84@yahoo.co.uk