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81
British Bikes / Re: What is this BSA Frame??
« Last post by john.k on July 29, 2025, 01:57:56 PM »
The toolbox is correct for the plunger frame ,its odd its mounted cockeyed .........BSA had the forge shop to make the frame ,a part of their heavy weapons plant..........BSA also drop forged the flywheels ,even the lowly side valves had forged steel flywheels........in fact you can make a very capable OHV from a BSA M20 or M21.
82
British Bikes / Re: What is this BSA Frame??
« Last post by cardan on July 29, 2025, 12:26:10 PM »
Hope your friend wasn't expecting more... a bitza can be fun but very disappointing if it's a surprise.

Leon
83
British Bikes / Re: What is this BSA Frame??
« Last post by peteR on July 29, 2025, 11:37:39 AM »
Thanks guys.  I have managed to find the frame number hidden away.

The frame number B3-593 from a 2.5HP 1934 BSA Blue Star 250c.

Agree that the plunger section is probably from an A or B series.  The forks actually seem to be C15 and the front wheel is Bantam D1 with the smallest brake imaginable!

Other than that, it seems to be just as it left the factory!
84
British Bikes / Re: AJS 16M 1951
« Last post by john.k on July 29, 2025, 11:06:43 AM »
The CP Burman boxes dont normally chip gears ,as the gears are quite soft to avoid breakage ........the worst can happen is tooth breakage caused by worn layshaft bushes..........good news is millions of these boxes were made in WW2 ,and NOS parts are cheaply available .........be aware though there are several changes in the whole gearset made in WW2 to meet criticism of too wide gaps in the ratios............In general ,there are prewar trials ratios,post war trials ratios,and standard road gears.
85
British Bikes / Re: AJS 16M 1951
« Last post by dynamic on July 29, 2025, 08:47:04 AM »
small metal fragments found in g/box oil so an inspection will be the next move
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British Bikes / Re: What is this BSA Frame??
« Last post by john.k on July 29, 2025, 01:00:11 AM »
The motor leans forward because the original motor had the magneto at the front ,with space at the back of the crankcase ...........the mega dollar BSA ohv V twins use the same frame backbone ....J 12 and Y 13 ...and sell for mucho dollars
87
British Bikes / Re: What is this BSA Frame??
« Last post by john.k on July 29, 2025, 12:50:50 AM »
Its not surprising the motor has been replaced ......the mid 30s BSA singles were not a very good motor ,in fact they were crap .......a very poor effort from such a big maker............which is why they brought in Val Page to redesign all the BSA singles to be decent bikes.......Yes ,I had a couple of 1934 Blue Stars ,good gearbox ,crap motor.
88
British Bikes / Re: What is this BSA Frame??
« Last post by cardan on July 28, 2025, 11:56:00 PM »
This sort of thing - this one is a 350 from 1936 - but there were lots of variants.
89
British Bikes / Re: What is this BSA Frame??
« Last post by cardan on July 28, 2025, 11:51:13 PM »
Hi Pete,

What a ripper! The main frame is certainly BSA, very likely from a vertical-engined model with the oil in a "sump" out the front, early-mid 1930s. The best plan is to decipher the frame number - on the forged steel backbone somewhere - then have a look at a list of BSA frame numbers to see what comes up. https://www.bsa1930s.nl/engine-and-frame-numbers/

The rest of the bike has been "added" to the older part of the frame. Worth leaving as an interesting mix.

Cheers

Leon

[Ed: took me a couple of goes to spell decipher!]
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British Bikes / Re: What is this BSA Frame??
« Last post by R on July 28, 2025, 11:23:29 PM »
1920s BSA's had an I-section backbone, but I'm not sure if it was like that.
Something about Francis Barnett's "built like a bridge" comes to mind also,
with all those bolted joints ?
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