B31 mystery?

[trophy]

Hello all.  Fingers crossed you can help.  A couple of days ago I became the owner of a very original 1955 B31 with frame/engine numbers CB31 10836/BB31 19613.  The V5 says that it was first registered in England in 1985?  Could this imply that it may have started life abroad?  and if so how could I find out?
With the bike came 90% of a B33 engine, number BB33 860774, the last two digits are barely readable but that's what they look like to me.  What year would it be.  Can the B33 engine fit into the B31 frame?

[idie]

1985 was when the old green cardboard log books ceased to be used and everything was centralized in the DVLA as it was then called. New V5 paper documents were issued. If you were late in registering the bike by that date. It could be re-registered with a new number. A B33 engine is almost the same as a B31 so will exchange with no problems.

[JulianS]

The BB33 prefixed engines were made between 1953 and 1957.

The numbers went up to the 8 thousands only so the hard to read final charaters may not be part of the number.

[Bess]

Hi,
    It maybe worth asking BSAOC for a dating certificate which will give you when is was made, if the engine and frame were originally paired and where it was dispatched:

https://www.bsaownersclub.co.uk/machine_cert.php


Best wishes...

[martinh10]

From the Engine/Frame No. listing on the Draganfly website (I tried to load it here but it was too large) it would appear to be a 1957 engine. A word of caution though, the BSAOC dating certificate for my B31 doesn't quite tally with this list.

[Pete A10]

The Frame and B31 engine numbers tally for a 1955 sprung bike i.e. Aug 54 to July55.
The B33 engine would appear to be 1956, i.e Aug 55 to July 56

[trophy]

Thanks everyone for your very helpful answers to my queries.  Most grateful to you all.  Here is another one. The  side stand was supplied loose as the lug on the stand arm had broken off. That's no problem as I can easily weld on a new one, but there is no sign where the other end of the spring fits on the frame.  A photo or sketch would be helpfull.

[JulianS]

The end of the spring is anchored on the part of the stand lug which bolts to the lug on the frame.

[trophy]

The end of the spring is anchored on the part of the stand lug which bolts to the lug on the frame.

Very grateful for the above JulianS.  A picture is worth a thousand words.  Will sort it out ASAP. Also thanks to:-
Pete A10 for the B31 and B33 engine dates, have since found and downloaded a list from the web.
Bess for recommending getting a dating cert from BSAOC, will certainly do that,
idie for reminding me that 1985 could be when the log books changed.  A dating cert from the club should sort that out.
Thank you all.