Frame number request for info.

[David Samways]

The frame definitely has nothing to do with B34-1 - they're completely different models with completely different frames. Attached pic shows B34-1 frame.

Having done a bit more research (I love a mystery!), your machine bears an uncanny resemblance in all respects to the 1931 B31-1, or if it originally had an OHV engine B31-2. The forks and the headlamp bracket in particular look the same and B31-2 clearly has a sidecar lug. Attached are catalogue pics of B31-1 (SV 250) and B31-2 (OHV 250). I don't have a parts book for 1931 so don't know what the frame looked like, but the catalogue pic clearly shows a pump clipped to something just under the tank of B31-1 and B31-2 looks like it has a tube just above the engine.

I don't know what the B16049 number stamped on the steering head means, my '32 and '34 machines don't have any numbers there. Maybe BSA stamped the model number there on pre-32 machines, perhaps someone who knows more about this can comment. I would say that all the evidence shows that B16049 has nothing to do with the year of manufacture and frame number.  What's far more interesting and perplexing of course is that fact that you have a Z3 stamped into the rear of the frame. I don't suppose the frame number could be Y2 or Y3 rather than Z3?

Hope this helps - best regards David

[David Samways]

Pic of B31-3 which would have Y3 101 frame number.

[jh1]

Cheers David and Julian 👍
Very recent updated details from a friendly knowledgeable source shows that
Headstock Frame ident No B1 6049
was belonging to a
B34-2 250cc from June 1934 which went to a Somerset dealer.

Just for info - The pump under the tank is a my addition - and not part of the original framework bike.

In my readings about early post vintage bsa models they have year stamps 1931 a Y ... 1932 a prefix of  Z....
As year stamps / identifiers
a) under the seat on the down tube for model / frame age identification.
b) engine casing
Moderner bikes have a year / model identifier stamped into the headstock.
Hopefully this is correct - so according to documented frame and engine prefixes - my bike numbers stamped on frame and engine begining with prefix letter Z followed by numbers do confirm it to be a 1932 model L with mixed frame and engine. That has been restored using original parts where possible.
And now with a known modener headstock 👀 possibly ....
I am learning as I go and thank everyone for all inputs.
I'm going to owe many beers 🍻🍻

[David Samways]

But there's no possible way that it's a B34-1 it's a completely different machine with a completely different frame and engine configuration see my previous posts and attached pic. From your pics I'd put money on B31-2 or B31-3 - double check that frame number, are you sure it's not a Y?

[JulianS]

Dont think it is B31 1 or 2 or 3. Steering head tube different at the ends.

1931 parts list pages below.

[David Samways]

Couldn't find a pic of the B31-3 frame alone, but this interesting drawing clearly shows dual frame top-tubes 

[David Samways]

Dont think it is B31 1 or 2 or 3. Steering head tube different at the ends.

1931 parts list pages below.

Doesn't frame 27-5591 look like the right one Julian? From the photos it looks like a good candidate - certainly a much better candidate than 29-4040!!!

[jh1]

27-5591 would be my choice as well.
Even down to the 2 holes cleary shown on parts diagram built into the seat post tubes that can also be found on my actual frame.

Looks so similair to the schematic above -but - the schematic has no holes in the seat post area .
🍻

[David Samways]

Cheers David and Julian
Very recent updated details from a friendly knowledgeable source shows that
Headstock Frame ident No B1 6049
was belonging to a
B34-2 250cc from June 1934 which went to a Somerset dealer.

Just for info - The pump under the tank is a my addition - and not part of the original framework bike.

In my readings about early post vintage bsa models they have year stamps 1931 a Y ... 1932 a prefix of  Z....
As year stamps / identifiers
a) under the seat on the down tube for model / frame age identification.
b) engine casing
Moderner bikes have a year / model identifier stamped into the headstock.
Hopefully this is correct - so according to documented frame and engine prefixes - my bike numbers stamped on frame and engine begining with prefix letter Z followed by numbers do confirm it to be a 1932 model L with mixed frame and engine. That has been restored using original parts where possible.
And now with a known modener headstock  possibly ....
I am learning as I go and thank everyone for all inputs.
I’m going to owe many beers

Just another observation and bit of empirical evidence  :The frame number on 1934 models was stamped into the lug under the seat. Attached is a photo showing a B34-1 frame number. Frame numbers are configured as date letter, model number, then a dot followed by a three or four digit number.

Again, I think you're barking up the wrong tree with the number stamped into the headstock.

[David Samways]

Just a correction. The frame number location on B34-1 models mentioned in my last post is wrong. It looks like it was stamped into the bottom lug of the front down tube just forward of the engine.

David

[jh1]

mmmmm.
The letter looks stamped and to my old eyes the digits look raised, I'm sure I'd read that raised digits were associated with mold numbering rather than year / model information that was stamped into the frame - like the B in your picture looks stamped into whereas the numbers look raised.
It's definately a B and definately stamped.

[David Samways]

That's a nice clear photo. I would say that it's definitely not a frame number, and that it's probably been stamped in at a later date. Look at the style of the numerals, I think they're what typographers call "sans serif" whereas the frame VIN has serifs.

[JulianS]

It certainly does look like the 27 5591 and 15 5599 frame illustrations. I think you have solved it.

[David Samways]

The numbers in my photo are all stamped BTW.

The parts you are talking about are all forgings rather than castings. Generally, it's more common for forgings to have raised part numbers since the die is stamped or engraved with the number which then shows as the inverse on the part. On a die-casting (such as timing case castings) the same applies, but on sand castings it's more likely for the part numbers to be depressed.

I can't find any numbers on the frame forgings for the L32 but the top member of my 34 Blue Star has "BSA" and the part number in raised letters/numerals. On most other BSA parts the piled arms, BSA and sometimes a part number are neatly engraved or punched.

[David Samways]

Just to satisfy my curiosity, could you post a photo of the Z3 frame number?