The ignition fuse blows after running for a minute or two

[jurgenkoppen]

Hi guys, I finally got back to my 79 XS650 and did the starter fix, new clutch plates and the clutch rod seal. Starting her up, she ran fine, nice idle, charging and revving OK, but then it cut off, with a blown ignition fuse. I have a Pamco system, which works like a charm when all is well, but adds to my confusion in trying to find the culprit. I inspected the wires, nothing unusual or indicating contact to ground so far. It has been two years since this bake was on the road...so a major clean-up of all contacts and grounds is most likely needed. However, if there is a typical fault causing the ignition fuse to pop only after running for a minute or so, I would be keen to learn about it...and resolve the issue.

 

[gggGary]

After a minute or when you turn the handle bars?
A cut wire where they go through the back of the headlight shell is a guess. The rubber edge protectors for those holes can rot or come loose.

 

[jurgenkoppen]

After a minute or when you turn the handle bars?
A cut wire where they go through the back of the headlight shell is a guess. The rubber edge protectors for those holes can rot or come loose.

Thank you Gary, I had opened up the headlights and so far checked already once, but will have another fresh look. I also will pull out the old rusted back fender to replace that, and to access the regulator which I got with my Pamco back in in 2017, which is mounted just over the sway bar bushing area...

 

[gggGary]

Is this a special, with a four fuse box or is this a separate fuse just for the Pamco?

 

[grouchie83]

Is it just sitting there idling when it dies? With no user input?

 

[jurgenkoppen]

It was just sitting there, once it fired up nice and easy with my starter no longer grinding ( finally) I took it off the center stand, rolled/pushed it backwards to get it out the door, and gone was the ignition fuse. I replaced it, started and ran again, no movements of the bike and died again with both main and ignition fuse blown. It is a xs650 Special with a 4 fuse box and a separate Pamco fuse. It has a PM Alterator.

 

[gggGary]

Got, get a volt meter on it, watch as it runs/blows fuses. A good way of looking for shorts is a turnsignal bulb wired with alligator clips.
without it running remove one fuse at a time clip the bulb across the fuse clips, a really bright bulb is probably the circuit with the short.

 

[Jim]

It's possible for an old(er) coil to short itself out when it gets hot, then return to not-shorted once it cools down.
Not a "common" failure mode, but it does happen from time to time.

What happens if you replace the fuses and just turn the bike on? Don't start it, just key on. Does it blow the fuses then?

 

[jurgenkoppen]

It's possible for an old(er) coil to short itself out when it gets hot, then return to not-shorted once it cools down.
Not a "common" failure mode, but it does happen from time to time.

What happens if you replace the fuses and just turn the bike on? Don't start it, just key on. Does it blow the fuses then?

It does not blow any fuses when the ignition is turned on, but is NOT running. Right now I cannot even start it anymore, the starter no longer responds to pushing in the starter button....I will rig up the light bulb with the alligator clips later today The coil theory seems to be the only plausible one, since the fuse only popped after running for 20 seconds. I will get to the bike later today, I am about to remove the rear rusted fender to replace it and to get access to the regulator, which came with the PMA kit (or was it with the Pamco conversion, it has been 9 years ago, could not find the emails regarding that conversion)

 

[gggGary]

Have the battery charged and load tested. A bad cell?
Confirm solenoid operation, that the contacts are releasing.

 

[jurgenkoppen]

Have the battery charged and load tested. A bad cell?
Confirm solenoid operation, that the contacts are releasing.

After moving and tucking on the wiring in the headlight bucket to find possible chaffing ( there was none) and also examining the wires from the PMA, which run under the clutch rod and then behind the drive chain area ( maybe the chain made contact?), but no, all good there. I had the tank off to check the wires to the coil, all good. Battery fully charged, fuses replaced. Then I turned on the ignition, pressed the starter button again, nada, and then just for the heck, I did it the other way around: Pressed the starter button and then turned on ignition key........and she fired right up!!!! WTF? I had her running happily, charging well, ( I have a handlebar charge indicator full on green, two bars) . Ran out of gas without my tank on, put tank back on, and again, running as if nothing had happened, revving, idling.... So now I am suspecting the ignition key module, maybe some corrosion inside...she has been sitting all last year, albeit under the shop, not outside. I will put her all back together and see if I can do a short test ride...not too far for starters, just in the yard. Thank you all for suggestions and moral support, you guys rock!!!

 

[ckahleer]

Do you have a DVM? Most have a 10A setting. I would put it in series with the fuse and see how much current it is drawing.

 

[jurgenkoppen]

It looks like I am out of the woods. I put in a better battery as well, and now she has been behaving, starting right up and going pretty good up and down my 2 km backroad driveway. She is just like any other lady, I suppose. I neglected her last year, and now she needed some extra attention to be cooperative again...my philosophical take...