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1938 BSA M series frame/engine info required

Hi all.
Can anyone help with identifying correct frame/engine number match for my 38 BSA M20 or M23.
Frame number is JM19 300
I have a bsa records doc stating it was a BSA M23 empire star. There is a tally no. of 4493 (what is tally no?)The engine has been changed but in 1942 the bike was registered with engine number JM23 159. I believe this was the correct and original engine to the bike but would like to know for sure.
Can anyone help please.
Marcus

email (option): Marcus@glassenbury.plus.com

Re: 1938 BSA M series frame/engine info required

Hi Marcus.
The 'JM19' frame prefix was used for 5 different models in 1938, the M19/20/21/22/23. The only way to know for sure what model the bike started life as, is from the factory records! If you have confirmation of this being a 'M23 Empire Star' from the factory ledgers, then this is what it is/was and 'JM23' would be the correct engine number prefix. The numbers that you have quoted look to be both original and correct for this bike. Nice! What engine is currently fitted? Regards, Pete

Re: 1938 BSA M series frame/engine info required

Hi Pete.
VMCC supplied a certificate I guess from factory records stating that frame number was a M23. It would make sense that the engine number 159 would be lower as like you said the JM19 frame was used for quite a few models.
It currently has a M21 engine fitted. It was first registered in 1942 and declared ex government on the old buff log book. I am not sure when the engine was changed but it has maintenance unit and broard arrow markings on it. Military style headlamp and the panel in tank is blank. It was registered to RAF Hullavington.
I just wondered if any BSA factory records would show that the M23 engine number I have and frame were together. I know I will not find the original engine so will most likely leave the M21 in it for now with a view to put a post war ohv engine in the future.
Regards. Marcus

email (option): Marcus@glassenbury.plus.com

Re: 1938 BSA M series frame/engine info required

Hi Marcus, have a good look and see if your frame number is JM19 800 rather than 300.
The BSA despatch book gives frame JM19 300 as being fitted with engine JM23 486, that bike was sent to W Duff and sons in London (15/11/37) who were the export agent which BSA used to ship bikes to Malaysia. Not sure that the occupying Japanese gave us our bikes back after grabbing Singapore.
However engine JM23 159 was fitted to frame JM19 800, which was sent to Kings, Oxford on 8/10/37.
I don't usually gamble, but I know which I'd put my money on...
Rupert.


Re: 1938 BSA M series frame/engine info required

That’s interesting. Frame is definitely JM19 300 as the 3 has a flat top to it unlike the curve of an eight. It is very clear.
The vmcc history record also says it went to Duff and sons. Where do you guys view these records?
I have had vmcc tell me in the past that a ZM21 engine was dated 1946 but I know ZM prefix was 49 onwards?? No disrespect to vmcc.
Surely the frame number would be higher than engine number as frames were produced for all models and engine model designation slower. It has been suggested that the bike was taken by the government before being registered hence first registration 1942??

email (option): Marcus@glassenbury.plus.com

Re: 1938 BSA M series frame/engine info required

Rupert
Hi Marcus, have a good look and see if your frame number is JM19 800 rather than 300.
The BSA despatch book gives frame JM19 300 as being fitted with engine JM23 486, that bike was sent to W Duff and sons in London (15/11/37) who were the export agent which BSA used to ship bikes to Malaysia. Not sure that the occupying Japanese gave us our bikes back after grabbing Singapore.
However engine JM23 159 was fitted to frame JM19 800, which was sent to Kings, Oxford on 8/10/37.
I don't usually gamble, but I know which I'd put my money on...
Rupert.


Hi Rupert. I have just re read your message. So as you say frame JM19 300 went to Duff and sons as the vmcc certificate says. Bike does not appear to have been overseas as 42 registration confirms but it seems I may not find out what happened with the bike in the late 30’s and 40’s or what went on regarding the engine numbers? Unless both bikes JM300 and JM800 ended up in government use and engines were changed in workshops??

email (option): Marcus@glassenbury.plus.com

Re: 1938 BSA M series frame/engine info required

Hi Marcus, I have no further information on which to base any conclusions so only speculation is possible.
Flat topped '3' or not, mistakes in stampings, paperwork and registrations seem to be more common than might be expected, plus the possibility of numbers being altered at any time after the bike left the factory.
To me the key fact is that the 1942 registration gives the engine number as JM23 159, which was supplied new with a frame number remarkably similar to the one you have, and the alternative bike in the 'frame' was most likely sent half way round the world.
Plenty of "yes, buts" attached to that, no way of now being sure.
Rupert.

Re: 1938 BSA M series frame/engine info required

What I find amazing is that people actually expect that a frame will have the same engine in it after 80 years.
Back when my A 10 was daily transport I had 3 engines for it
The original which went in for the annual inspection, the monster high compression mismatch of all sorts of parts which was usually in there for hooning around on plus the spare for when the hot engine went bang big time.
In the 70's & 80's Australia was awash with bike breakers chockers full of British bikes from the 20 through to the 80's.
And from what I have gleened from period UK bike publications the situation in the UK was some what similar for bikes that survived war time scrap drives .

Re: 1938 BSA M series frame/engine info required

trevor
What I find amazing is that people actually expect that a frame will have the same engine in it after 80 years.
Back when my A 10 was daily transport I had 3 engines for it
The original which went in for the annual inspection, the monster high compression mismatch of all sorts of parts which was usually in there for hooning around on plus the spare for when the hot engine went bang big time.
In the 70's & 80's Australia was awash with bike breakers chockers full of British bikes from the 20 through to the 80's.
And from what I have gleened from period UK bike publications the situation in the UK was some what similar for bikes that survived war time scrap drives .
I think the want for correct engine type and number prefixes etc is mainly for the interest of collectability and value. As I said, for my bike, I will run it with the M21 engine and later may fit a post war ohv. Nice to have a choice!! Whatever engine is in it it won’t ride much differently. It does genuinely interest me to know what engine was fitted originally, and thanks to forums like this one some info can be obtained.
I am sure a lot has happened with my bike in its 80+ years that I will never know.

email (option): Marcus@glassenbury.plus.com

Re: 1938 BSA M series frame/engine info required

Trevor,

I don't understand why you think that is amazing. I have about 30 pre war BSAs and save for 2 all have the original engine and frame combinations. Since I want to ride my bikes as well I have not always used the original engine cases as some have been damaged by the mag being loose on the platform and causing havoc on the cases like on my Y13. Since parts availability was difficult after the war these bikes were patched up as much as possible so there were some improvements (like I would do on a contemporary bike) to keep it running or make it more rideable (like a simple twist grip instead of the horrible internal twist grip set up). Even if the engine was changed over, often the owner kept the original engine. Maybe I was just lucky or maybe things are not as bad as you think.

Regards,
Leon

email (option): leonhop3_at_planet_dot_nl

Re: 1938 BSA M series frame/engine info required

Anyone out there happen to have a JM23 engine for sale or just the crank cases ?

email (option): Marcus@glassenbury.plus.com

Re: 1938 BSA M series frame/engine info required

Leon KM20.1478
Trevor,

I don't understand why you think that is amazing. I have about 30 pre war BSAs and save for 2 all have the original engine and frame combinations. Since I want to ride my bikes as well I have not always used the original engine cases as some have been damaged by the mag being loose on the platform and causing havoc on the cases like on my Y13. Since parts availability was difficult after the war these bikes were patched up as much as possible so there were some improvements (like I would do on a contemporary bike) to keep it running or make it more rideable (like a simple twist grip instead of the horrible internal twist grip set up). Even if the engine was changed over, often the owner kept the original engine. Maybe I was just lucky or maybe things are not as bad as you think.

Regards,
Leon
I suppose it is just about how people used their motorcycles.
Down here they were used as daily transport, in the USA seems to be weekend warriours.
And then there is mileage
Down here we tend do a lot of miles and if the bike is a ride to work vehicle then you fix it as fast & cheaply as possible.
Then they get passed down to the kids and often become paddock bikes so same story.
Never many friendly BSA dealers but lots of British Bike wreckers.

I have 14 pre WWII motorcycles in various state of completeness and dissrepair
None of them have engine & frames that belong together , some are the right models but none are matching years.
2 x A 10's 2 x A 7 & 6 unit singles again all mixed & matches.
In fact the only matching numbers are the WM20 , the C10L, B 50 & A65L .

It could also have a lot to do with the registeration systems used down here
Before Harleys became the most popular bikes to steal ( still are ) british bikes were tops on the light finger list.
And up until the late 80's you could pinch a bike in NSW , then swap the engine with another pinched bike and rebirth them both in Victoria or Queensland .
After the 90's you had to change the numbers but it is no hard to add another number or letter into a BSA stamping.
Because computers were used and because the police refused to accept offers from various bike clubs to sort out potential rebirthing something like WM20 777777 could be changed to AWM20 777777 or WM20P 777777 or even WM20 1777777 and all of them would pass right through the system .

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