BSA Owners' Club Forum

The BSA Workshop => Singles => Topic started by: chrisgoodwin on 24 April, 2017, 23:09:15

Title: B31 Sparks & Lights
Post by: chrisgoodwin on 24 April, 2017, 23:09:15
Hello all,
After working abroad for the last 15 years I am finally back working in the UK and have pulled the B31 (Rigid 1949) out and am embarking on a full re-build.
The bike is complete and I do not expect many surprises along the way, but I know the mag was iffy, the dyno does not work and I really fancy decent lights and a reliable spark.
Can anyone help with the following questions please?

Can I replace the cam & spring engine shock absorber with a cush drive to allow an alternator fitting & Subsequent electronic ignition?

Has anyone any comments on the magdyno replacement units for sale on the web?

Any ideas to banish the prince of darkness and appease the spark fairy are most welcome.

Title: Re: B31 Sparks & Lights
Post by: TTJOHN on 25 April, 2017, 08:20:43
Welcome back. I am a little confused as to why you would want to change the original set up on your B31, just send your mag & dynamo off to Tony Cooper in Halesowen telephone number 01615592405 for refurbishment and they will be like new again, you could change the lighting to LED from Dynamo Conversions Ltd, Pete will put you right there.

Regards TTJohn
Title: Re: B31 Sparks & Lights
Post by: JulianS on 25 April, 2017, 12:23:53
To fit a crankshaft mounted alternator is a massive task, if it even can be done.

Firstly the current drive end shaft is not suitable for an alternator rotor and would need to be changed for the later shaft fitted in 1958/59 when alternators were used.

Second you would need to replace the primary chaincases for ones which would allow for mounting the alternator stator and fixing the stator.

Third you would need a clutch with built in cush drive.

No doubt lots more practical issues.

Many of us are using Lucas dynamos and magnetos without any problems - thye just need to be in good condition.

I  used my A10 with magneto and dynamo (on 12 volts) for commuting to work - shift work in all winds and weathers over many years until retirement 4 years ago. No electrical problems. Bright lights.

You could replace the mag part of the magdyno with a modern self generating BTH unit

You could use an Alton alternator with it.

These modern items cost around 1000 plus VAT.

Or you could just get your magdyno reconditioned for less.

I have had good service from Andrew Guttmann at Priory Magnetos.
Title: Re: B31 Sparks & Lights
Post by: STAR TWIN on 25 April, 2017, 15:02:21
My B31 runs happily on a refurbished mag and 6 volt dynamo. I always run with the headlight on having had the cr** scared out of me by one myopic car driver who didn't see me. One caveat regarding LED headlight bulbs. The beam pattern is hopeless for night riding. I do use an LED stop/tail light though. 
Title: Re: B31 Sparks & Lights
Post by: chrisgoodwin on 25 April, 2017, 23:03:23
Thanks for the comments, they have brought in mind a statement from my old metal work teacher circa 1973 "The easiest solution is possibly the best solution". After some initial research from the web sites provided- the mag dyno (With probably 12v conversion) seems quite attractive, and reliability of a re-built mag seems to have little concerns.
But, I am sure I will return to this subject, so far the B31 re-build consist of the delivery of my new shed and trying to find a cheque book to join the BSAOC, but hey one step at a time!
Thanks again for the replies