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#767925
03/12/19 6:39 pm
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Joined: Sep 2017
Posts: 1
Lew M
OP
New poster
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OP
New poster
Joined: Sep 2017
Posts: 1 |
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 Re: BSA Engine
[Re: Lew M]
#767928
03/12/19 7:07 pm
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Joined: Feb 2011
Posts: 3,265
Boomer
BritBike Forum member
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BritBike Forum member
Joined: Feb 2011
Posts: 3,265 |
Definitely built for racing. Is that a bronze head? That dual float carb was usually used for alcohol or dope fuel and seen on the old JAP speedway engines. It has a '49 and older timing cover but the mag is mid '50's. The barrel and head do appear to be something special. Maybe someone's one off racer.
Bill B...
PS: Just noticed the drive side and the breather with the model "KM23" stamped. The breather I believe is prewar and a KM23 is a '39 500cc Silver Star.
Last edited by Boomer; 03/12/19 7:07 pm.
Boomer
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Re: BSA Engine
[Re: Lew M]
#767929
03/12/19 7:53 pm
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Joined: Sep 2001
Posts: 2,961
Gordo in Comox
BritBike Forum member
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BritBike Forum member
Joined: Sep 2001
Posts: 2,961 |
A quick online search comes up with many articles of the 1939 BSA KM23 Silver Star.
Gordo
The roadside repairs make for the best post ride stories.
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Re: BSA Engine
[Re: Boomer]
#767947
03/12/19 11:14 pm
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Joined: Nov 2011
Posts: 5,317
Magnetoman
BritBike Forum member
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BritBike Forum member
Joined: Nov 2011
Posts: 5,317 |
Given the bronze "beautification" of various tidbits on that engine along with the fact that, to the best of my knowledge, BSA didn't list a bronze head upgrade, my guess is it's the stock cast iron head with a coat of bronze paint. The fact that by then BSA had the technology to cast Al heads (for the Gold Star), and that 1939 was pretty much the end of the line for anyone using bronze for heads anyway, also makes painted cast iron more likely.
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Re: BSA Engine
[Re: Lew M]
#767948
03/12/19 11:32 pm
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Joined: Nov 2012
Posts: 1,098
koan58
BritBike Forum member
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BritBike Forum member
Joined: Nov 2012
Posts: 1,098 |
Is there anything inside it?
Were the oil pumps so unreliable that it was important to have a gauge to check that the pressure hadn't dropped from the usual 5psi?
At the very least, it's a lovely historical monument.
The cast in breather? at the top of left case is unusual, is that moulding found on later cases?
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Re: BSA Engine
[Re: Lew M]
#767953
03/13/19 12:03 am
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Joined: Sep 2001
Posts: 2,961
Gordo in Comox
BritBike Forum member
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BritBike Forum member
Joined: Sep 2001
Posts: 2,961 |
By the XB engines in 46/47 the breather was lower down behind where the crank came out. The pre-war knob was gone but that new knob stayed there for years. Gordo ![[Linked Image]](https://i.postimg.cc/HVf4nwX0/IMG-0518.jpg)
The roadside repairs make for the best post ride stories.
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Re: BSA Engine
[Re: Gordo in Comox]
#768067
03/14/19 3:23 am
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Joined: May 2004
Posts: 4,053
BSA_WM20
BritBike Forum member
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BritBike Forum member
Joined: May 2004
Posts: 4,053 |
Gordo,
According to what is stamped on the crankcases it is an M series heavy weight not a B series sports engine.
M's breather remained on the top of the case till it moved down to the timing cover with the upgrade to tele forks.
Nick
Pre WW II M series de-luxe models had a tell tale button where that pressure gauge is.
Actually I think they were a bit higher up.
They remained on the De-luxe models only till WW II when they were dropped, never to appear again.
Originals are only found under rocking horse poo and the repo ones must be made from solid gold.
Bike Beesa
Trevor
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