1982 Maxim XS400 blowing main fuse

[John-Paul]

So i was riding about a month ago, going over a hill when my bike died out on me. Pull over, tear it apart, find the main fuse blown. Replace the fuse, blows instantly as soon as I turn the key.

I then found a melted connector under the gas tank, so i walked the bike about a kilometer home and replaced the connector with shrink butt connectors.

Blown again.

I notice the starter relay wire is messed up so I replace that, new bolts and hardware for everything to do it right.

Blown again.

So i bought some cheap 20A fuses and I unplugged things in the headlamp until it stopped blowing. So far the only one that stopped it from blowing was the main plug. (red, brown + blue) no duh, that takes away power from the whole bike anyways.

I am beyond stumped. I've been looking all over this bike and I can't figure it out! Someone please help

 

[amc49]

So it's impossible for the main ignition switch to be bad itself?

And you never wondered why that melted point did that? As in trace that wire to see what it goes to.

 

[John-Paul]

Sorry forgot to specify. That melted connector was due to a zip tie that fell loose and it melted from the engine heat.

I'm not sure if the main ignition switch is the issue, because it could also be because I'm taking all the power away by unplugging it.

 

[amc49]

Here's the deal.

Wire is mostly inert and causes no issue if you or whoever has not abused it to shove more power through it to melt or let the fasteners go bad to let wire then move around a lot. That knowledge can remove a lot of searching effort. Switches by what they do lend toward issues as they wear out and can even come apart with people forcing keys in tumblers that have tightened up from weather exposure. It's too much trouble to relube the switch and where America and the common man goes.

Don't forget a major point on main harness, the flex point where it goes by the steering head and has to change angle every time you move the steering one way or the other. That one bit me once after a complete bike rebuild and I anchored the harness down too hard and too close to that flexing point and broke wires inside the overall cover to strand 50 miles from home.

Don't know about that one but many ignition switches can come apart if you are careful and then you can check out the circuits inside and I always grease contacts up a bit to forego corrosion and make it work smoothly for a long time. The Hondas I work on a lot are well known for the bottom of switch coming loose to do things like that, the OEM ones are much harder to do it but the Chinese replacements so many spring for use substandard plastic that is too soft and it comes unsnapped to let the contacts fall apart. Needless to say walking time and the switch is often hidden on the bottom and hard to find that error.

In your case I would likely weed the main switch out before I went further. If you see any burning inside that may lead you elsewhere. Looking under any seat that folds up can bring rewards too, wires getting pinched doing that.

If you don't know how, take the trouble to learn to read a voltmeter, you don't nearly need to be a brainiac to use one and the most used skills are self taught in 5 minutes, the meters are dead cheap too. You will never ever use 9/10ths of the things a VOM can do and it still pays for itself almost the first time you use one. After that it is virtually $50 in your pocket every time you turn it on.

 

[John-Paul]

By the main switch, we're talking about the ignition switch, right?

I'm decent with a meter, i just don't know the best way to use it in this scenario.

 

[amc49]

Yes on the switch.