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I've got the chaincase off the WM20 to check the oil leaks.
I can't find any up & down play by grasping the mainshaft. There doesn't seem to be leakage around the mainshaft, however there's a bit of end float. I can't measure it but by eye it's about 1mm.
Oil leaks from the larger bush, a few drops over several hours with the bike on the mainstand. A fair bit more when on the sidestand.
Can anyone say whether this is about normal or should the box be examined?
Bob the main source of leak is usually through the open bearing. The current trend is to fit a sealed bearing. The sleeve gear bushes will let by also if worn. When assembling the box, all three shafts should be set to about 7-10 thou. The main shaft is nipped up at the kick start end through the small bearing, so effectively there shouldn't be any end float at the clutch end. Ron
Thanks for this, Ron.
And the other leak in that area, the chaincase. There are threads here about sealing the chaincase but I haven't seen any mention of preparing the mating surfaces of the chaincase halves. The surfaces on mine are still painted, I'm thinking of taking them back to bare metal to see if this works better with a sealant.
I never use sealant, it's a right bugger up when you want to remove it next time. The cork gasket is quite thick and my trick is to glue it to the outer case with Evostick and then smear axel grease on the gasket face before assembly. I nip the screws and go round 2-3 times nipping them further. I've had the same gasket for many years and a very minimum amount of leakage. Ron
Ron is right about the use of sealant. My outer case is glued fast. Even bought another outer case in the even I destroy one getting it off.
My bike had not been run for many years. My gearbox was tight, but after a 50 miles or so it leaks so bad I have to carry a little bottle of oil to top her off.
No sealant on the cork gasket to the inner cover !!
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Hi Bob and everyone else.
It's good you have that oil leak. It lets you know you have oil in there. It also acts as a
"Tell Tale" your box is empty when it stops dripping. That way you are "forced" into
maintenance. See? There is a purpose.
BTW, That "oil leak" as you call it was installed by my great grandfather Nigel Fenwick's company. He invented it
and convinced all the British Motorcar and Motor Bike companies of the need for oil leaks way
back in the early years. All those guys were invested in the fledgling oil industry back then and it was a
clever way to sell more oil.
My Great Grand Father was a smart man, but his stroke of genius was to marry young Nellie Bly. She is the genius
behind Joe Lucas as it was her who taught him to put smoke into wires, but her fame was stolen by men. The same
sort of thing happened to Marie Currie as you know. Every time you get a "short" you see the smoke escaping
right? Have you ever seen "electricity" escape? Smoke can escape with such force it can make a huge bang and flash
of light, but it's really smoke.
Moral of the story? There's a reason and purpose for everything. Thank my grand parents for their
contribution to your riding pleasure.
:joy: :joy: :joy:
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Thanks for these replies folks, be assured I see your point.
Only a bugger to get off, Ron? It's a sight worse than that. I too bear the psychological scars inflicted by trying to separate chaincase halves held together by sealant.
Charlie, you may need to carry an angle grinder with you in case you ever need to take yours off by the roadside. I suppose you can get battery powered ones?
And Robb, I had no idea of your distinguished ancestry. To every thing, etc, etc,
I've done what you suggest before, Ron, & used adhesive on one side of the gasket & grease on the other. I just used multi purpose grease, I might try something thicker.
You really need to use high melting point bentonite grease .
Commonly used for car wheel bearings .
General purpose lithium grease is jus not up to the job, or rather the solution agent is not up to the job.
And British bikes leak oil.
Back when they were made roads were not fully sealed and most driveways were gravel.
Hell , the 70's Rolls Royces we used to use for wedding car hire all leaked oil ( no seal on the crank )
So it is a proud British tradition to leak oil .
You will go mad trying to prevent any oil dripping out.
When new the counter shaft sprocket ran closer then 0.001" to the gear box case.
Now days most cases are flogged out to at least 0.005" wich makes it next to impossible for the scroll to keep on pumping it back into the box
WM20's did not have a design life of 80 years and if the DOD found one to be leaking too much oil then they would have rebult the box into a new case .
Scrols & slingers have a finite service life before the wear overwhelms them .
Whilst I'm happy to accept a small degree of leakage from my British bikes the M20 gearbox oil loss can rapidly become damaging and it's best to try and control it...If you really want authenticity and run an M20 without a sealed main gearbox bearing I'd recommend checking the oil level frequently...Very frequently...About 250-300 miles is all you need for the level to drop from the correct level to a point where damage to the gearbox is possible....The sleeve gear bushes tend to be the first thing to go...
A rubber sealed main bearing (with the inward facing seal removed before fitment) more or less eliminates the leakage problem and reduces the need for such frequent checking and the likelihood of the need for a gearbox rebuild...One disadvantage of 80 year old motorcycles is that they pre date the introduction of modern oil seals!...The sealed bearing part number is 6205 2RS and being a metric bearing is readily available from any bearing supplier...
40 or 50 SAE engine oil is the correct lubricant for the BSA gearbox...Ian
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And definately no thickening agents or anti leak addatives lest you end up learning the fine art of rebuilding BSA horseshoe gear boxes.
According to the speedo, this box has done about 40 thousand miles in 22 years or so. I have a rebuilt one to replace it with so that'll go in & I hope it leaks less. The old one will get a sealed bearing.
I quoted an incorrect number for that gearbox bearing...It should be 6207 2RS...NOT 6205 2RS...Sorry!....Ian
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Thanks for the correction Ian.
While we're here, another question. The sliding plate on my inner chaincase has one open & one closed slot to accommodate the securing bolts.
Parts lists show open slots on both ends so I can't get an idea from them. Which end of the plate, open or closed, should face which way? I can't see that it makes any difference but perhaps I've just had a boy's look.
Because I was trained in engineering sciences I look for anything that can go wrong.
SO when I do mine the closed end goes to the back lest a thrown chain possibly pick up the open end.
I also fit a loose nylon tube over the spacer tube to prevent a loose or collapsed chain eating through the steel