Main fuse blows when stopping

Hey folks!

New to tinkering, but I'm managed so far to replace my clutch cable and repair a worn wire that was causing by bike to turn off when turning.

But now I'm stomped... Shortly after fixing the above-mentioned wire, my bike blew it's main fuse. Funnily enough it turned out to be a 25A fuse instead of the 20A that the service manual lists,

I checked for loose wires that could be shorting, and taped off a few loose ends. Installed the spare fuse, and managed to ride a few kilometers, but the fuse blew again. I managed to scrounge up a bunch of spares, and started troubleshooting, but I'm seriously stomped.

On the middle stand, the bike runs fine. I've wiggled every wire, tilted the bike every way, moved the handle-bars etc and it just keeps going.

But as soon as I take an actual ride, at the very first intersection where I have to stop, as soon as the bike is idling with the clutch in, it switches off and I find the fuse blown.

Any ideas where to start looking or how to trouble-shoot this issue?

It's a 1982 KZ550 that I have big plans for...

Thanks, G.

Could you be dealing with a short in the brake light wiring? What happens if you hold the brake while it's on the stand, does it blow the fuse then?

I don't know the wiring on your particular bike but on mine it seems that power to the brake lights is fed through the switches to the bulbs, so if there was a short between the switch and the bulb you'd be having a dead short when you close the brake light switch but no other times. There is probably enough resistance in the stock wiring that it doesn't just instantly blow the fuse so I would imagine you might be able to get to a stop before the fuse blows.

Past that you're probably going to have to dig up a wiring diagram for your bike and start tracing through it.
What wire did you repair already?

I'll test the brake on the middle stand tonight; it sounds about right!

The wire I repaired was a white one... I was assuming it was the kill-switch, as the bike would turn of when it lost contact, but no fuse would blow.

I never considered that the fuse might hold out for a few seconds and then blow, so I probably didn't test that properly.

Thanks for the tip, and I'll post back with my result!

if not the brake light check the charging sys mine had a short there when i would come from i higher rpm driving and come to a stop the bike would over charge and blow the fuse it ended up blowing the rectifier sorry if i said that wrong but i had to wire in oen off a diff bike and go to blade fuse's after that

gilimanjaro wrote: Hey folks!

New to tinkering, but I'm managed so far to replace my clutch cable and repair a worn wire that was causing by bike to turn off when turning.

But now I'm stomped... Shortly after fixing the above-mentioned wire, my bike blew it's main fuse. Funnily enough it turned out to be a 25A fuse instead of the 20A that the service manual lists,..... .

Be sure to install the correct 20A fuse. The po may have used the larger fuse as a band-aid, instead of fixing a problem.

I agree with the brake light/light switch theory. With It running on the center stand, did you run it through the gears or just leave it idling?