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[Thack]

The term "tripping out" confused the heck out of me, too!



I'm with jaffa90 on this: I strongly suspect the battery voltage is falling away when the lights are turned on. This would suggest an almost flat battery; or a high resistance somewhere in the earth return path to the battery.



It could be a short, but I think that would blow a fuse.



So, I'd stick a voltmeter across the battery when the engine is ticking over and measure the voltage. Then I'd switch the lights on and see what the voltage falls to. If it falls a lot (below 10V, say), I'd suspect a faulty battery or faulty charging circuit. If it doesn't fall much, I'd be looking at high resistance connections in the paths from the relays to the battery earth terminal and the lights to the battery earth terminal.

[Michael]

Cheers Thack... gives me something to work with at least Multimeter ahoy

[jaffa90]

You can check for faulty fuses, batteries, regulators, rectifiers, magnetos, alternators, earth leakages, battery drainage and most components with a multi/meter and save pounds.

[Michael]

IF you know how to and what to check for Jaffa... I dont really know what to look for in a faukty battery other than low voltage and not holding charge. Regulators, similar except checking for 14 volts or so output. Rectifiers, ac in dc out, but not really sure how to check... etc. Earth leaks, other than a visual, no idea.

[Frank]

Not sure why you say the problem is caused by the rear light, surely the headlight comes on too and so could be the cause? Given that a bad earth in my bike's lighting circuit caused the engine to cut out, horn and starter to fail I don't see why it couldn't also cause a fuel pump to fail. Can you run a separate earth direct to the pump to see if it's then OK. If it is you would have proved an earth fault in the original wiring. Norm's suggestion of the pilot lights is possible, they are the most flimsy wiring imaginable. Eliminate them by disconnecting. Burning relays out is a bit worrying, are the replacements rated enough to take the load?

[Michael]

I think its the rear light set because the brake also (and most commonly) causes the fault to occur

[Michael]

Oh... and a few weeks ago when the relay burned out, I also lost all rear bulbs, but front were fine

[Michael]

OK, some battery voltages for a clever person to analyse... voltage across battery with everything off 12.5v, key only on 12.5v, pilot lights on 12.3v, then with main beam on 11.95v, and then with high beam on 11.9v. Putting a flasher on drops to 11.8v. Brake light on its own 12.2v, with main beam is 11.9v...




Now with engine running... 13.2v at idle, 12.6v at idle with main beam on, 12.4v at idle with high beam on, down to 12.1v with flashers on too. Brake light in addition to all above takes it to 12v. At medium rves we have 13 to 13.5 volts. So... do these numbers mean anything to anyone? Intermittent cutting out fault didnt happen during these tests...

[jaffa90]

Well done, 12.5v without switching on is passible for a top up lead acid battery 12v 5ah kick start ONLY bike like mine, your E.F.I. electric start should read minimum 12.7v and have a battery 12v 14ah (is that your battery? ). At medium revs (3,000) you should have 14v with all lights (no load) off. Try again and simulate vibration with moving wires and rear lights.

[sofiaspin]

Michael - I have just bought a low mileage 2008 500 classic converted to 50s trim and with a small fortune spent on paint, tank, carb, exhaust etc. It runs superbly and was very good value. Will you bit the bullet, so to speak?