BSA Gold Star identification

[guest1828]

I am trying to identify what I think is a Gold Star special.  It appears to be a 350 sleeved down to 250.
The engine number is EXB.225 which does not line up with any of the engine numbers I can find.
The gearbox number is HEE 384, and it also has Albion H5S MK2 cast on to the gearbox cover.
The bike is fitted with a BTH mag and an Amal  10 GP carb with matchbox float and an electronic rev counter.
I cannot find any frame number and it would be interesting to know who built it.
Bike details in programme when raced are ‘250 BSA Gold Star Special’.  I think it may be a 1959 engine and could have been supplied direct from the factory as I don't believed it has ever been road registered.  I'd appreciate any information about the bike.
Thanks  Keith

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[Oldtimer]

Got me baffled. Certainly a DBD engine with a squatter barrel making the engine a short stroke. Don't think it was supplied from the factory. Try asking the Gold Star owners club they are sure to know.
If you do find anything out let us know as it looks very interesting.

[Oldtimer]

Hi RoadRocket,
Any news on the motor. Looking closer at the top picture the cylinder base flange looks a lot thinner than a DBD barrel.

[spooky]

Could the `EX` part of the number mean the motor was exchanged in it`s early years ?

[Smithy]

Everything about the bike screams home-made special. Shortened barrel, Albion gearbox, featherbed style frame. If you have no luck with the Goldie Owners Club try Classic Bike magazine, they have extensive archives and some c=very knowledgable writers.