B24 1937 350

[Matt H]

Hi All

Could someone confirm which oil to use in the Gearbox on my B24 1937 Empire Star?

Currently im usingXL Castrol 20/50 classic ( same as i use in the engine) but understand people also use grease with an oil mixture?

I have got some Castrol XXL 40 monograde oil for the gearbox or Castrol Classic ST90 Mineral Gear Oil which is aimed at Straight cut gears.
Which one would suit?
Cheers

[Matt H]

 ;DAnyone??

[Steve.S]

Hi Matt, I only have experience of the earlier 4 speed gearbox, but I imagine the internals are the same.
BSA recommended 50 grade oil. I think the only reason others use grease is to stop oil leaks. I would avoid using a mixture of oil and grease, but you could try thixotropic grease if oil leaks are a problem. I don't know if your gearbox has a sprocket oil seal, but if it doesn't, you could fit a double nitrile sealed sleeve gear bearing. This will stop the leaks in my experience.
I don't think you need to go to the expense of using ST90, but 40 grade might be a little thin. What does the book say? I've not heard of anyone using multigrade, but what do I know? I doubt if any of these oils would cause a problem, but personally, I'd stick to BSA's recommendation, just to be safe.
It may be interesting to note that BSA recommended D140 for the earlier 3 speed box, but it makes the kickstart a bit sluggish in the winter.
Hope this is helpful.

[Matt H]

Thanks so much for your response very helpful. The gearbox is not leaking at all which is great and in very good order I just felt like when the gearbox was warm, it was harder to select the third and fourth gears.

Although I don't have direct experience with old bikes. I do have a lot with vintage and veteran cars, and I know the information in handbooks was for then and not now as I found out multiple times.

I've bought a litre of Castrol ST90, which is for straight cut, gears, ideally and not hypoid and I put the oil level five mil higher than it should be. Now the selector is so much smoother than before, after 10 miles has been completed and now is a joy to select the gears, I didn't realise it could make that much difference, but I just felt that the oil level in the gearbox was a little low considering where the level bung plug is.

Once again, thank you so much for your info