Just waiting for Martyn to return Carb then I can try and start my 1940 M20. I replaced the plug cap and lead and turning the engine over got a spark at the plug. Considering it has been standing since 1968 I am pleased and surprised, well it is a start, maybe I will have to overhaul the mag dyno but not this week.
I have found that the oil I added to the gearbox seams to be running out behind the gearbox sprocket. Is there a seal in there and how do I replace it after taking the box out?

email (option): araine11@hotmail.com

Hi Arthur..There is no seal in the WDM20 gearbox..You can either run 'as is' and check the oil at 350-450 mile intervals maximum (it leaks out that fast!) or you can fit a 6207 2RS 'sealed' main gearbox bearing which is the accepted 'fix' for thisproblem..That will require a complete strip down of the box though...Ian

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

Thanks for the info Ian. I have not had a box like this apart before. Is it something an "amateur" should/could tackle or is it best left to experts. If I were to tackle the job is there a written guide I could down load? Where would I get the sealed bearing and does it need a press to fit it?

email (option): araine11@hotmail.com

Arthur,

I'm a novice to this M20 restoration but have just managed to completely strip the gearbox and refit the main bearing with ease, so long as you keep all the 3 shafts in 1 piece when you retract them so that the layshafts remain in tact then you should have no problems.
I did us a press to remove and refit the main bearing, but it isn't that tight a fit and you could use a pillar drill if you have that option.
Good luck.

Julian

email (option): 79Aust@sky.com

Julian thanks for the info. Did you use a combined bearing/oil seal. If so where did you get it?

email (option): araine11@hotmail.com

Hi Arthur..The gearbox main bearing is a Metric one so easily obtainable from any bearing factors..The number is 6207 2RS..2 RS indicating 2 rubber seals...
The bearing on the other end of the mainshaft is an Imperial one but still available..No. LS7..Heat the gearbox main casing before knocking out the old bearing. Reheat it and cool the bearing in the freezer overnight before refitting...You'll then be able to do it without a press or similar...Ian

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

Hi

I have heard of people packing the gearbox with liquid grease to prevent this.

Any one tried this?

Kind regards

Pat

email (option): sacombsashtrees@hotmail.com

I wouldn't recommend that personally. The BSA box is designed to operate with oil, not grease and anecdotal evidence from other forum members confirms my suspicions that the grease will not reach all the areas that require lubrication...Ian

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

It depends on how much you use your bike.
If you do long rides the the box gets hot enough to melt the grease sufficiently to get into all the right places.
If you do short trips or long trips in short legs ( one hour or less in the saddle ) then the grease will not get hot enough to do its job and it will be curtins for the layshaft bush, layshaft fork and the sleeve gear bush.

I used grease in mine when I rode it at least every two weeks and we usually did long rides oft with spels of 200 km or more. Even better was I had to keep in contact with the A10 & A 65 riders so the box got worked hard.

For the last few years it had only done a couple of short runs each year and a couple of rallys ( ABR & BSA Nat ) neither of which have a lot of long rides. So now I have a rebuild job to do replacing all of the above mentioned parts + bearings.

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