AJS & Matchless Owners Club

I've just had to renew the battery on my G80. The battery went totally dead whilst in the pub after a run. I started it with jump leads but it blew the headlight bulb on the way home and I wondered if it had cooked.
When I got it home I found the battery would not take any charge.
I have just fitted the new battery and checked the charging voltage and it goes up to 18V on a battery that was 14.7V to start with.
Does anyone have any how the voltage on an alternator charged motor should go ?

Thanks

Ian

Reg/rec knackered?

Thats what I suspect , I'd just like some confirmation. I have spoken to a couple of people about replacements. The first told me that measuring the voltage with a DVM was no good it would get interference from the engine and I needed a moving needle analog one to check the voltage , the other guy said they only made regulators for rotating magnet alternators as per Lucas

So is yours an excited field alternator or permanent magnet? How many wires come out of the regulator

www.electrexworld.co.uk/
Electrex make good reg/recs. Its just knowing which one is best for the Matchless. DaveEdited by - dave16mct on 11 Aug 2012 08:34:57 AM

Id say your Voltage Regulator is toast. Anything amiss with the battery will fry it, I blew one up by shorting the positive terminal to the frame with spanner, and another went when the battery collapsed. Get a proper one or you will be scratching your head figuring out how to use a universal one.

A digital meter should be fine for checking the electrics over. As said above, the rectifier/regulator unit sounds favourite here. Also agree that Electrexworld will be able to fix you up. If you know the wattage/amperage of the alternator and the number of wires leading from it it would be possible to adapt a rec/reg unit from some other model. As it's a Rotax engine some of the older Aprilia Pegaso/BMW F650's might be worth a look.They are relatively common too so that means more spares options available.
14.7volts should be the most you see when you run the engine, any more will damage other bits e.g. the headlamp bulb! that (maximum) figure is the same with lights on or off. Typically most similar bikes would net go quite so high on the voltage with the lights on, but anything over 12.5 (still not over 14.7!)volts with maximum load (i.e.lights on) is acceptable

I agree that the regulator is kn**kered, but find the replacement is not so easy. The regulator on there is obsolete and even secondhand all the ones available are in France and seem to have a suffix on the part number. In spite of the schematic wiring diagram showing a 3 wire set up this doesn't appear to be the case, as checking I only seem to have two wires giving 18V+ AC and tracing the 3 wires from the alternator the third ones joins into a pair that disappear into the loom.
Has anyone successfully replaced the regulator on one of these ?
Ian

I got my last new one from B. J. Bikes & Bits triumph@britishmotorcycle.com.au , They get them from LF Harris as far as I know.

I also vote for a knackered Reg /Rec and I highly recommend Electrexworld. Give them a ring and discuss your requirements. The guy there is very knowledgeble and helpful. Almost all modern reg/rec units are "Shunt" type and in my experience have about a 5 year service life. The ones supplied by Electrex world are, I believe the Mosfet type, which run much cooler and are much more reliable.

Ian