B31 valve cap missing?

[robatlangtoft]

Hi there,

I'm new to forum usage, so apologies for any blunders.
I have recently bought a B31 1955 vintage, in a fairly original but quite tired condition.
I find there is a valve cap on the exhaust valve only. Could this be correct or has the inlet cap been omitted somewhere in it's history?
Thanks in advance for any help.
Would anybody like to explain why they are apparently not fitted at all, in the Gold Star versions?

Regards      Rob

[idie]

If it's any help my 1955 B33 has never had them in the 40 years I've had it.

[Ian C]

I've looked at parts books from around 1954 and lash caps are listed for Inlet and Exhaust on both B31 and B33. But in a 1958 parts book lash caps are only listed for B31. You can never assume that everything in parts books is accurate though!! FYI BSA part nos. 31-0103 (Inlet) and 65-0209 (Exhaust).  HTH

[robatlangtoft]

Thanks fellas,

Great to know they can run OK without caps. I have actually ordered one for the inlet and will fit it, but it's comforting to know that serious damage caused by the missing item is unlikely.

I'm puzzled by how large the gaps were when I took the covers off. (guesstimate 2mm or more!) I just hope it isn't camshaft bearings failing.
It's certainly going to rattle less when I run it next time.

Regards          Rob

[Ian C]

Have you removed the timing cover and inspected that area? There should be seals in the timing cover for the oil feed to the cams. These seals press onto domed screws which have a hole drilled through them. Oil is then fed directly to the cam.

[robatlangtoft]

Hi Ian C,

Thanks for the reply, and advice on the oil feed to the camshaft.
I am having a look in the timing side this afternoon, as I seem to have a problem of oily grime in the dynamo (which I cleaned, but not thoroughly, just a few days ago), and I'm wondering if it is managing to migrate into the dynamo from the timing chest.

The replacement valve stem cap just arrived. It's titled as advertised from Nick Avery, NSA Motorcycles, "Inlet valve stem cap 65-0209"? so I will have to do some checking, as you have that number as the exhaust cap?

Regards        Rob

[Pete C]

The valve stems are of different diameters so you should be able to tell by the fit, or not, if it is the correct one.
A cap for the exhaust will be too large for the inlet, they should be a snug fit on the valve stem.

cheers

[robatlangtoft]

Thanks again for the info.

Inlet valve cap now fitted, but having removed the timing side cover another little mystery is revealed. Several mangled chunks of rubber loitering about.
I'm guessing they are the remains of an oil seal from behind the mag drive gear? Both of the cam shaft feed seals are in place and complete.

To be resumed. I have now ordered a parts book, so hopefully can get a bit better organised and prepared.

Thanks for the help. Regards.    Rob

[Pete C]

If you need to replace the magneto drive sprocket oil seal, go for a modern lipped type rather than the original. A CR 8088 seal will fit .

Cheers