550 k3 electric failure

[Harold 400/4]

Was out on a run on the 550 yesterday. It was running really well for 25 miles or so. First hint of trouble was when it hesitated, backfired, but then it was fine. I came to a junction, and the electrics completely died. Pushed it to a layby, and the main fuse had blown. Replaced the fuse but still absolutely dead.

I've checked the battery which seems ok, and even tried a spare charged battery, but nothing. Have taken the earth lead from the battery off where it connects to frame, it looked ok but I cleaned it anyway. Still nothing.

I'm after some advice as to what to look at next?? I was thinking fuse box terminals and ignition switch. How would I go about testing these? I have a multi meter, but pretty clueless tbh.

Anything else obvious I should be looking at?

Any advice gratefully received. Cheers.

[matthewmosse]

On my 550k3 the ignition switch could loose it's connection whilst being turned on, worth just spraying wd40 in where the key goes and operating the switch a few times. Look over the connections in the loom and do similar, e.g. wd40, unplug and 're plug a few times. It might help. Also just have a good look everywhere the loom might rub against the frame or tank, on my gs125 I found the tank had rubbed through the main loom. Also check the red wires by the charging system, if I recall correctly, red with white stripe has a tendency to corrode at the ends and fall off it's terminals.

[hairygit]

Have a good look at the fusebox too. The bits of copper that hold the fuses should be bright and clean, any discolouration increases electrical resistance. Do not automatically assume that a "new" fuse cannot be faulty, they can be, and least to much head scratching. Test the fuse, with a multi meter or a battery and bulb and a bit of wire. If the fuse holding bits of copper are dirty, clean them thoroughly (2 bolts to remove fusebox and disconnect the multi plug to get it off the bike) If the fuse checks out as okay, then as Matthew suggested, check ign switch and the wiring to it, especially where the loom goes near the headstock, wires can break inside the loom from fatigue, especially if it's the original loom.

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[Harold 400/4]

Thanks Matthew and Hairy. Good advice. Had a look at the fuse box and there is some corrosion, so will give that a clean up. Also some fuses have wrong ratings so will replace. Tried the wd40 on the key trick. Left it a while, turned it on and off a few times, and blow me, back to normal!
Think I'll go over the other connections as well to hopefully avoid future problems.
Cheers for the tips.

[hairygit]

if you put some vinegar in a cup, and stir in as much salt as it will dissolve, then dunk the fusebox in it for 20-30 mins, it should come out bright and shiny, then drop the plug into it to clean the terminals in there.