G12 650 CSR Alternator

legg · Post by **legg** » Thu Aug 12, 2010 9:50 am

I recently fitted a Sparx alternator kit into my 1966 Model 18; it dropped straight in with no mods or hassles. I read somewhere that the Sparx needed a large battery- I think 8ah was mentioned.

Don Madden · Post by **Don Madden** » Thu Aug 12, 2010 5:46 pm

I don't see any relation between output of a 12v system, which must have a diode or other regulator & the size of the battery. If running 6v, however, the battery must be large enough to accept the excess charge by converting the water to gases. I recommend to not connect stators with higher than original output as 6v nor to use any sealed battery on a 6v alternator system as the fluid cannot be replenished. Cheers, Don.

legg · Post by **legg** » Sat Aug 14, 2010 4:10 am

I'm certainly no expert on these things, Don, but the 6ah battery I originally fitted in October last year went open circuit a couple of months ago. I assumed (before I read that bit of info about the suggested 8ah battery) that I had cooked the battery with the large alternator and my illogical reluctance to ride with lights on during the day- the result of a youth spent riding old bikes with dynamos. The subsequently fitted 9ah battery is holding out well so far, and I am now (slow learner!) riding with lights on during the day. Much safer if you can do it, of course, and the halogen headlight shows up the 'roos and wombats at an impressive distance at night!Edited by - legg on 14 Aug 2010 03:12:07 AM

Groily · Post by **Groily** » Sat Aug 14, 2010 8:57 am

The advantage of a solid state regulator/rectifier is that the battery should be well-protected from excess charge, which it won't be at 6v with the old-style 3 wire stators and no proper regulation as Don implies. It should be protected with a rectifier and zener diode at 12 and is pretty much guaranteed to be with a modern black box.
Modern regulators are available for either system voltage, but I see no point in running alternator systems at 6 volt any more unless strict originality is very important. I haven't had a moment's battery trouble with 12v systems with solid state rect/regs - fingers firmly crossed.

Stephenwalls · Post by **Stephenwalls** » Fri Aug 20, 2010 11:08 pm

I don't know if it will help anyone in the future, but I fitted a Sparx generator (sorry Groily, but I thought it was worth the extra).....and it's great! The rotor was too tight to fit on the crank, but a lttle hone and its now a nice inteference fit. I took it out for a spin tonight (after taking the opportunity to give the chain case a shine!) and it works a treat. I'll measure the charge current over the weekend, but it looks like I can ride in the dark now!

Malleon · Post by **Malleon** » Sat Aug 21, 2010 1:00 am

quote:
Thank you all, gents.,
I will try to change the rotor if my supplier has an alternative which has clearance as per Don's recommendation.

Update:
Fitted another rotor courtesy of my supplier, problem solved and excellent results.
Original rotor had an enlarged keyway, thus preventing a secure fitting.
Thanks again to all.

wilko · Post by **wilko** » Sat Aug 21, 2010 2:27 am

How did you hone it? By hand with emery paper?