Hitchcocks Forum

Hi All, I wonder if anyone can help with a charging issue I've got? The set-up is a 1992 Bullet 500 with a new higher output alternator stator from our hosts, Boyer Brandson powerbox (over a decade old), brand new battery and halogen 55/60w headlamp. The bike starts and runs fine and does show a small charge on the ammeter with no lights on, but a large discharge when I turn the headlight on, regardless of revs. I'm getting 5 amps and 25 volts from the alternator at medium revs (I am on the original rotor, but it will support it's own weight from a steel bar, so I'm guessing it's magnetism hasn't leached away), but only 1.5 amps (through the red lead to the battery) and 13.5 volts from the powerbox at medium-high revs regardless of load. I have fitted a 10A fuse in the red powerbox lead as recommended, which hasn't blown. I would have thought this set-up would easily have coped with the more powerful headlamp bulb, so my question is shouldn't I be getting more current from the powerbox to the battery? Is it fried or am I barking up the wrong tree and should be looking for another problem? Many thanks in advance!

First thing if you haven't already, check the earths.

From the symptoms l don't think your problem is over regulation, l think there is a short somewhere in the headlamp wiring or bulb or connector. Just to confirm, the discharge is when headlight on and engine running at medium revs? REgards, Mark

Mark - Obviously there's a discharge when the engine is off but yes, engine on at medium revs. Small charge with light off and large discharge with headlight on.


Interestingly, the bike has recently had the headstock bearings replaced at a local shop (thought he couldn't very well fail it's MOT on that issue again if he fitted them himself!) so I'll check all the connections again - it does look like a bit of a rat's nest behind the headlamp! Cheers.
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Interesting what you said about headraces. I'm not sure about lndians but Redditch Bullets earth through the frame, headrace bearings not being a good earth path! Try rigging a temporary earth (just a loose wire will do,) from headlamp to battery and see if that helps? REgards, Mark

So is the battery going flat,the fact you are getting 13.5 at the battery indicates it is charging, my guess is the ammeter is just reading the usage of the headlight because of the way it is wired. I can't remember but I thought a 92 had an A/C headlight and if this was the case wiring has been altered. Could be wrong

The battery is brand new and I plug in a conditioner when it's parked, so haven't had the opportunity to find out if the battery goes flat yet. It's a DC headlamp on my bike. Will try the temporary earth trick tomorrow. Thanks for the help, will keep you posted with the results.

Sadly, the temporary earth didn't help. The light output has always been good. Even the speedo bulb appears to have a good earth. All the other connections appear OK. No obvious shorts. Thinking about it, I don't understand why the ammeter would show a greater current draw if there was poor earthing. I did do A-level physics, but that was a very long time ago now.....

Well it was worth trying! I've re-read your posts and had a thought, has the ammeter been removed or rewired at all? If the ammeter has had it's polarity reversed you would see what you're seeing, a slight discharge at tickover (alternator output usually doesn't quite balance at low revs,) and a proper charge at full revs with lights on. I'm not familiar with the wiring on these so if anyone sees a flaw with this idea please say. I'm curious that you've recently had work done so I'm wondering what might have changed.

REgards, Mark