Hi BSA hive mind,
I am looking for a replacement alternator for a C25 engine. The wiring on the existing one is very badly chewed up. I know that I can repair this (see RR) but not having used the bike for many years I might go to a lot of trouble only to find that I need a new one anyway, so I thought I would bite the bullet. But which one to buy? The code on the existing is 43204B which has as an a modern equivalent the Lucas RM19 (I think - please correct me if I am wrong). The C25 was a 12v and the 43204B (RM19) was/is a 6v but you join two of the three output wires together it "miraculously" becomes a 12v (electronics is not my strong suit). RM 19 alternators seem to be twice as expensive as, say, RM 21 alternators, which are two wire output 12v items.
Is an RM21 a suitable replacement for my bike? Please forgive any laughingly ignorant explanation above,
Kevin
PS - Once I have solved this mystery I will need help with the standard wiring diagram to incorporate a regulator/rectifier and electronic ignition (and electronics is not my strong suit)
Hi again,
this looks like a topic for which very few want to offer an opinion. Where might I get some advice about this?
Again, if you can help, thank you,
Kevin
Hi Kevin,
Google Paul Goff. He has the full range of alternators and regulators etc. I would go for the 12v alternator with modern rectifier/regulator. The RM21 should be a direct replacement for the RM19 but Paul goff can be contacted for advice.
Dave.
Modern 12v reg/recs are very simple, usually 4 wires.
2 x AC going in and + and - coming out.
Depending on polarity requirements, (ie pos or neg earth) you can take either if the latter pair to earth.
Good question, as I have just replaced my old three wire stator for a two wire one, as I didn't think it was charging. I have put a new two wire one on there but could not get ignition circuit, lighting circuit is fine, it does have a relay regulator on it but I don't think it's working, I have just ordered a new one from Goff together with a diagram of how I should wire it in, so that I can get ignition. I'm looking forward to see if it turns out okay.