Blowing MAIN Fuse

Fergal · New Member Joined: Nov 21, 2008 Posts: 1

I have a fuse problem Question

I have a very nice 1978 XS 650 Yamaha I'm getting ready for a local bike show. My problem is that I keep blowing my main fuse. The bike started just fine a few weeks ago. It started every time I tried it until I killed the (NOT VERY GOOD) battery. After the battery went dead I jumped with the battery from my Road Star. It was then that the fuse blew and now, every time I turn the key on ... POOF ... another fuse blows. I checked all the wires from the main fuse and I can't find a brake in the wire or anything. I'm baffled, any help as to what I may have done and any suggestions as to how to fix it? Please help
Thanks Dave. Crying or Very sad

xsleo · Posted: April 10, 2009, 4:16 pm Post subject: Re: Blowing MAIN Fuse

Could jumping it like that short out the rectifier? If it did then you may need a new one. Try unplugging the rectifier, and turning on the key. If it don't blow the fuse then the rectifier may be bad.
I replaced mine with Pamcopete's Radio Shack $6.58 replacement. It takes a little work, but it is easy.

BT650 · Full Member Joined: Jun 09, 2009 Posts: 10

I have that exact same problem with my 79. Everything worked great until my chain broke loose and bent my clutch pin (whole nother story). The bike was running, turned it off like always and now every time since - turn the key and zzzzap goes another main fuse! Any other ideas?

gordo · Posted: June 10, 2009, 9:24 pm Post subject: Re: Blowing MAIN Fuse

BT, I suggest you check the wiring for the rotor & stater down at the sprocket area, most likey have a pinch there.Ferg, like Leo said, try that.

Retiredgentleman · Posted: June 10, 2009, 11:19 pm Post subject: Re: Blowing MAIN Fuse

Fergal;
If the fuse blows when the ignition switch is turned on, that means 1 of the 5 loads fed from the switch is shorted to ground.

The 5 loads are regulator, tailight, ignition coil, headlight, and misc such as turn signals, horn, brake switches. If the bike is a 78SE, you have fuses for the ignition, headlight and miscellaneous. Remove all 3 of those fuses and unplug the regulator. If the fuse blows, then the fault is in the tailight. If fuse does not blow then plug in the regulator, and see if that blows the fuse. Just keep testing by process of elimination. The kill switch allows you to eliminate the coil/coils as the faulty load.

If its a standard with only one fuse, then its just a little more difficult to check each load. Test by disconnecting each of the loads in turn.

dpmphoto · Posted: June 12, 2009, 12:09 am Post subject: Re: Blowing MAIN Fuse

Unplug your stator and turn the key.I doubt that its anything other than your stator or regulator/rectifier.Been there, oh and dont jump your battery charge it at 2amps

BT650 · Full Member Joined: Jun 09, 2009 Posts: 10

The rotor makes sense as everything was working fine before the chain came off and wrapped up and bent my clutch pin, so it probably pinched the wiring in the process. I'll try that tonight and let you know. Thanks so much for the responses.

BT650 · Full Member Joined: Jun 09, 2009 Posts: 10

Checked the wires to the stator and they were fine. Finally traced it up to the wires coming out of the bottom of the new speedo. They have some metal exposed where they go into the grommet on the bottom and it was touching the mounting bracket I made. As soon as I saw it, I knew that was it. Trimmed the bracket and she's all good. Thanks for the help though.

What Happened to 650rider.com?

Yamaha xs650