Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board 1925 tank caps

This is a long shot, but I'm looking for details on 1924/5 Model L (3.49 h.p.) tank caps. Even better would be a pair of them, but that's not likely to happen.

These are a threaded cap, not bayonet fittings.

As near as I can tell, they are 2" in diameter. I made impressions of the tank fitting using plasticine, and the nearest I can come to the thread pitch is 24tpi. It doesn't seem to match up to any metric pitch.

I have no idea why 24 tpi was used instead of the more usual 26 or 20, but perhaps it was a fine gas pipe thread.

It seems that 2" x 24 tpi is common on telescopes. Obvious, really

Hi Shane,
I own a model L (ohv) and have looked closely at quite a few of them over the last few years
None that I have seen have threaded fuel / oil caps, they have a bayonet type fitting
These caps are being reproduced as in the pics
I have heard of a story where a BSA in Aus or NZ that has had a brass tank fitted, The owner says it had it from new ??
I wonder if your tank has been remade or modified?
2 inch threaded caps appear every so often on ebay or get a hunk of brass and start turning ???

John

Thanks, John. I suspect the threaded cap was replaced by the bayonet fitting along with the various other changes introduced with the later short tank frame - 1926 or thereabouts.

Turning up a couple of caps is certainly an option - eventually.

I think I've died and gone to Heaven.

I've just found BSA Info NZ which has a great trove of BSA documents.
This includes 1920s parts lists, which aren't on Kim the CD Man's or David Brailey's DVDs
It's now bookmarked, and somebody will spend way too long downloading.

Anyway, it appears that the fuel and oil caps are the ones John showed above (S126), and they fit on screw-in filler necks (S127A).
The filler necks seem to be far closer to my current level of machining capability.

Any bike or progress photos? Not sure I’ve seen a ‘25 except in books! It must be a real challenge!

After being flooded in for quite a lot of last year, we've had quite a dry summer and were looking for more rain.
It's been overcast and rainy ever since KC asked for photos, and forecast to stay that way for most of this week.


It's not as much of a challenge as I thought it might be, but it was an older restoration and I'm not re-engineering it for a Cannonball Run.
Stub-mount AMAL 276 carbs are available, British Only in Austria had the clutch friction plates and a few other bits.
The tank which came on it seemed to be fibreglass which had been badly affected by ethanol, but turns out to have a steel inner with lots of resin to shape it. It would be usable, but the correct tank turned up on Gumtree. My luck ran out with the filler necks and caps, though.

If we have room, I'd like to take it to this year's BSA International. They're one of the more common Vintage BSA models, but you still don't see many of them.