Author Topic: Off-topic tech query (B31)  (Read 2563 times)

Online groily

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Off-topic tech query (B31)
« on: 19.06. 2008 07:18 »
I know many of us have other toys in the shed along with an A. I have just recently acquired an alternator B31 from 195?. Nice sister for and very largely the same as, my '59 A10. Quite pretty from about 3 yards, gets worse as you get near,  but loads to do to get it right in the mechanical and electrical departments, which are the only ones that interest me. I know many folk here have other machinery too, and I suspect there are a few B31s B33s around . . .  It doesn't seem, from my brief researches, that there is any forum anything like as good as this out there for the singles, although I may be missing something. Also, there seem to be no SRM-type specialists (perhaps because the singles are so reliable (ahem) they don't need it). But can anyone point me to either an informed forum or a comprehensive oily parts source? Sorry to infuse the pure world of the twin with the taint of the cooking single . . .
Bill

Offline LJ.

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Re: Off-topic tech query
« Reply #1 on: 19.06. 2008 09:42 »
Groily... As you know from my signature I have an M21. There is the M20 forum that I attend but sadly all the good information disapears after a few days, they need to get a format like this forum has. Although the 'M' seris is mainly a side valve, the bottom end is probably identical to the B31/33. Hope the following link helps

http://pub37.bravenet.com/forum/3155626639/1
Ride Safely Lads! LJ.
**********************
1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
1961 BSA A10  650cc Golden Flash-Blue
1961 BSA A10  650cc Golden Flash-Red

Online groily

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Re: Off-topic tech query
« Reply #2 on: 19.06. 2008 12:44 »
Thanks LJ, much appreciated. The bottom ends are pretty much identical (I think!). Looking at it one way, what I have is basically a swing-arm A10 with a sleeved down ohv M20 in it! ("Mainly a side-valve" reminds me that there was some variant with rockers, wasn't there?) When I bought the thing I've got (sight unseen) I didn't think I'd need to think about it too much - but sadly it has problems (don't they all?). While I can and have already taken most of it apart easily enough, there be things a person needs to know, and bits a person needs to get. Like ' should my piston have an oil control ring where there's a 3rd compression ring?' or 'Ought I to have a head gasket or could/should I lap the head on?' sort of things. I'll start by trying to get the service sheets or a manual. Can't believe I had one of these things before, about 35 years ago - but I've forgotten the little I knew at that time (which was precious little).

A very positive thing is that you confirm what I already believed - there are few places like this forum, where records are kept, civility reigns and knowledge is abundant! Thanks again.
Bill

Online Brian

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Re: Off-topic tech query
« Reply #3 on: 19.06. 2008 12:46 »
Groily my e-mail address is in my profile. Drop me a line, Ive been riding a B33 for many years and have had quite a bit to do with them.  Brian.

Offline Beezageezauk

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Re: Off-topic tech query
« Reply #4 on: 19.06. 2008 20:30 »
Hi Groily,

I have owned a B31 alternator model since 1974 and ridden it around the clock.  Like the subtle differences between a 59 and 60 A10, the alternator model B31/33's are different to the magdyno models in many ways. 

Be careful when obtaining spare parts and also state that whatever you require is for an "Alternator Model".

I have a spare parts list for these models so contact me if you require any specific information. 

Beezageezauk.

Offline a10gf

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Re: Off-topic tech query
« Reply #5 on: 19.06. 2008 21:22 »
Quote
there are few places like this forum, where records are kept, civility reigns and knowledge is abundant! Thanks again.

Thanks a lot for this comment, and thanks to the good folks here for making it a nice place.

e.

A10 GF '53 My A10 website
"Success only gets you a ticket to a much more difficult task"

Offline fido

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Re: Off-topic tech query
« Reply #6 on: 19.06. 2008 22:30 »
I had a 1954 B31 swinging arm for a few years and used it quite a lot, including a BSAOC International rally in Holland and a camping weekend in Cornwall (I lived in Nuneaton then so I didn't ride all the way from Scotland). I had a problem with oil getting from the engine into the primary case. There is no oil seal to prevent this but it turned out to be due to the driveside main bearing being loose on the crankshaft. I also had problems with poor quality pattern head bolts which fell to pieces. I think the M series engine has an extra main bearing compared to the B series. Although the B series was a new engine for the postwar range it has a lot in common with the prewar M23 Silver Star.

Offline LJ.

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Re: Off-topic tech query
« Reply #7 on: 19.06. 2008 23:32 »
Quote
I think the M series engine has an extra main bearing compared to the B series.

Fido... I also have heard of this and that the M series engines have four bearings, if it is so then the bottom end of the M engine is almost bomb proof. probably better than Gold Star singles.

A friend had a late fifties swinging arm B31 and was a magnificent machine. It did have an anoying oil leak somewhere around the rockers which we could never trace. Unfortunately the bike was sold on.

Ride Safely Lads! LJ.
**********************
1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
1961 BSA A10  650cc Golden Flash-Blue
1961 BSA A10  650cc Golden Flash-Red

Offline dpaddock

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Re: Off-topic tech query (B31)
« Reply #8 on: 01.07. 2008 15:56 »
Well, there is the BSA Forum for all models at

http://www.britbike.com/ubb/cgi-bin/ultimatebb.cgi?
David
'57 Spitfire


Online groily

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Re: Off-topic tech query (B31)
« Reply #9 on: 01.07. 2008 18:26 »
Ta for that dp, hadn't come across it so far. Now bookmarked.
Good news is I have managed to get all I need from Draganfly and Goffy, have managed to remake the through bolts that hold things together in such a way that the head and barrel can be attached properly without butchering spanners, and it will shortly be on the road. About a week I reckon. Piston that was in it was in fact from a 350 Ariel (which runs without an oil control ring), and getting sorted has involved replacing the little end along with the piston. Surprisingly thin-walled bush, I thought as I reamed it in this morning. The leccy bits are easy, as it has a later 2 wire alternator - just needed a regulator/rectifier, now fitted. Makes a nice change from my normal diet of AMC twins and the A10.
One of the joys of being in France is that the paperwork is quite easy for old bikes, especially if they come from the EU, and for I think a total of about 100 Euros I've got the papers in order and a French registration doc. Insurance will be less than ten quid for the basics. So a few quid on bits to get it right in the oily department, a few quid for the bureaucrats, and off we go.. Fingers crossed!
Bill

Offline royboy

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Re: Off-topic tech query (B31)
« Reply #10 on: 25.09. 2008 22:35 »
LJ YUK still going strong.
regards

Offline LJ.

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Re: Off-topic tech query (B31)
« Reply #11 on: 26.09. 2008 09:01 »
Well well... what a suprise! Did that oil leak get fixed? John and I would love to know where it was gushing from. Great to have you aboard Roy, and I will say once again that was/is a magnificent machine!
Cheers
LJ.
Ride Safely Lads! LJ.
**********************
1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
1961 BSA A10  650cc Golden Flash-Blue
1961 BSA A10  650cc Golden Flash-Red

Offline royboy

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Re: Off-topic tech query (B31)
« Reply #12 on: 28.09. 2008 15:31 »
CJ YUK still leaks oil a bit I think the rocker cover needs skimming. Primary chaincase has been modified so I can now get at the points. New front tyre, new clutch springs apart from that still the same as you last saw it. I agree with your description a magnificent bike.
regards