Electrical Fault. Where do I start?

On my MK3 I have an electrical short that occassionally kills the bike. The bike has all the latest 3 phase alternator, tri spark electronic ignition and matching coils. I removed enough old wiring to re-wire a 3 bedroom home but I now have this problem. When I turn the ignition key onto the position for the headlights the bike will run fine and then when I stop and come to an idle it sometimes dies. No spark!!
Then I turn the ignition off and put it into the run position with no lights and it will start. Mone the switch to the lights position and away it goes again only to die later on. I have replaced the switch and the new one does the same thing. Any clues on where to start looking for this problem please? Cheers Hillbone

Could it be your battrey hasn't enough residual power to run the headlight and ignition when at tickover as the output from the 3 phase is in deficit at tickover with the headlight on?

A similar thing happened to me when I used to run twin headlights on my JPN replica in the late 1980's. When I used to go to work at night, when I was in York negotiating the traffic lights, after the first few waits, it would die at tickover if I didn't reduce the "usage" by turning one headlight off.

So firstly I'd check your battrey and charge rate.

When the bike dies, how do you know that there is no spark?

When it dies, does the headlamp remain on and bright and will the horn still work, or has the whole system shut down which is re-booted by turning the key off and then on?

Check all your grounds.

Thanks for the replies. I had fitted a very expensive gel battery, so I was reluctant to think it couldn't handle a headlight at low beam. Will check that out as well as check headlight and horn when it dies.
Cheers

If you're concerned that your alternator isn't providing enough charge at idle with the lights on, simply check it with a voltmeter at different rpm and loads. If it's charging full battery voltage or better at idle with the lights on, then that isn't your problem.

That sounds fairly similar to - but a bit more extreme than - the issues that I am experiencing after installing a three phase Sparx alternator and regulator rectifier - see my previous posts. I am still finding that with the headlamp on, the battery is draining and therefore that the ignition loses spark (Boyer ignition). With the headlight on my ammeter (my 1970 has one in the headlight) shows minus 12 amps; that drops to just about 0 with it off, and ab out minus 6 with the pilot lamp on.

I have carried out testing on my alternator and know that a good charge is going to the Sparx regulator/rectifier; but at the moment I am thinking that for some reason the regulator is not picking up that the system is draining as much as it is, and is not allowing sufficient current from the alternator back to the circuit and the battery. Over Easter I went for a 1 hour ride with the headlamp on - ammeter showing minus 12 amps pretty much the whole time, and the bike stalled when I stopped in traffic on the way home; and the battery took over 4 hours on the charger to recharge.

I am tempted to say that the regulator/rectifier is just not working as it should; and I have emailled Tri-Cor who supplied it; I am waiting for a response. Is anyone aware of reasons why a regulator/rectifier would act in this manner?

Not sure if MkIII has the normally-closed kill button, but as my friend says, "They are diabolical." It is points-type, not a self-cleaning switch and on my '74, it was causing my bike to die, especially as the circuit heated and resistance would rise. You may have enough voltage to run the bike without lights, but as the electrical system is taxed by lighting and voltage drops, the bike could die. My bike would run fine, then stall without warning. If it sat for 10 minutes, it would start again, run a mile or two, then quit. I was cursing my new electronic ignition, but it was the feed to the ignition suffering a voltage/current drop through that switch.

I wired keyed power directly to the ignition feed under the tank with a 28-strand wire and cut out the cutout from the circuit. The bike has not quit since.

I also added another engine ground directly to the battery from the cases.

It's a possibility, anyway.
Mark

Didn't have spark on my bike, so I suspected the kill switch too. I knew that it would be bad since it's been sitting the last 20 odd years, but.... Damn !! the stripped screws added to the fun.






I'm having trouble getting the little micarta circuit board out. I got hold of it with a pair of needle nosed pliers and thought it would just pull straight up and out of the switch cluster housing but it doesn't want to let go.

cj, I think you should replace that crap.

chris, if your ammeter is going neg on you at highway speed, something is not right. Even my original Lucas 130W system charges, if slightly with the headlamp on. Either something is really draining the system, the alternator is not putting out full AC voltage/current or the regulator is not regulating properly. Only way is to test each part separately. If you need directions let me know.

Dave
69S