Author Topic: B40 (no) timing side gaskets  (Read 206 times)

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berniej

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B40 (no) timing side gaskets
« on: 14 February, 2019, 16:52:35 »
I called a supplier yesterday on receiving my engine gasket set to complain that there were no gaskets for the inner or outer timing side covers. He couldn't find the part numbers and, after searching, neither could I - seems BSA didn't fit them.

This seems very odd - the unit twins had them so why not the singles? The inner cover still needs to keep the gearbox oil and engine oil separated and both of them safe from the outside world - surely at least an inner gasket is required here?

Before I break out the Wellseal/Hylomar in hope of getting a good joint does anyone know of sources for gaskets here? Or is the cornflake packet the only option? (other cereals are also available).

Thanks,
Bernie
'49 M21/B31 hybrid
'56 M21 combination
Bantam D7
C15 project
B40 Sportsman project

Rupert

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Re: B40 (no) timing side gaskets
« Reply #1 on: 16 February, 2019, 21:27:08 »
The timing side jointfaces are not prone to leaking if they are in good condition and the inner cover is still flat, hence no gasket should be required. If you fit one it will effect the endfloat of the gearbox shafts.
If you want to make sure of oiltightness the best sealer I've found for that joint is Three Bond 1104, available from Rex Caunt.

berniej

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Re: B40 (no) timing side gaskets
« Reply #2 on: 16 February, 2019, 21:33:36 »
Thanks Rupert,

Part of the reason I expected a gasket is because one of the shafts does appear to be tightening up when I do a dry run test assembly.
Just the last nip of the rear cover screws causes it. A coat of gasket cement might provide sufficient shimming, I'll have to experiment I think.

Regards,
Bernie
'49 M21/B31 hybrid
'56 M21 combination
Bantam D7
C15 project
B40 Sportsman project

Rupert

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Re: B40 (no) timing side gaskets
« Reply #3 on: 16 February, 2019, 21:55:58 »
Usually that's due to the mainshaft thrust washer thickness, but if you've fitted a new mainshaft bush to the inner cover the flange on the bush may be thicker than the old one and cause the same problem.
Regards, Rupert.

AlanS

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Re: B40 (no) timing side gaskets
« Reply #4 on: 02 April, 2019, 14:56:04 »
Hi,
I have just spent a lot of time trying to sort oil leaks from the timing side of my 1964 B40, the bike is a re-import from USA that had been converted to side contact points, it leaked a fair bit of oil after a run.
I tried removing the covers, cleaning them and tried three different jointing compounds with little improvement. I checked the covers and found that they did not mate together well so decided to make a gasket.
Purchased two sheets of thin gasket material, cleaned the faces of the inner and outer covers, used a marker pen to coat the inner cover face, fitted the outer cover then used the outer cover as a guide to mark the outline for the gasket. This worked well and I could cut out the gasket to the markings acurately. This was cut out and became my keepsake template to mark an outline on the second sheet and thus cut out the new gasket.
Everything was reassembled successfully and I have done about 100 miles since fitting with mechanical problems and no leaks.
Hope this may be of help
AlanS

chaz

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Re: B40 (no) timing side gaskets
« Reply #5 on: 02 April, 2019, 15:29:27 »
depends on how thick a cereal box is used as to affecting engagements, if needed I use a sheet of A4 printer paper. generally a sheet is 0.1mm or 4thou thick and is thick enough to take up the  gap.when possible I put the casings down on a sheet of fine grade emery paper on a plate of glass and use figure of eight pattern with even pressure which helps. neither of my thunderbolts leaked a drop of oil and the T100 only leaks out of the clutch housing because the adjuster bolt has been well and truly glued in and I cant remove wiithout fear of cracking the case.

berniej

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Re: B40 (no) timing side gaskets
« Reply #6 on: 07 April, 2019, 08:32:20 »
Thanks all. I went the cereal packet route in the end with the addition of some wellseal. Fingers crossed!

Cheers,
Bernie
'49 M21/B31 hybrid
'56 M21 combination
Bantam D7
C15 project
B40 Sportsman project