main fuse blow

[Guest]

The main fuse blow on my gs 850L 1981. It back fire then blow. Does it sound like a charging system problem? The battery is in good condition.

[Brendan W]

Hi Justin, welcome to the Forum.
There are so many things that will blow the main fuse it's impossible to say what caused it straight off the bat. Electrical failures will obviously affect sparks and as they die off the unburned mixture can backfire. There is no way to fix this short of going looking for the fault.
In case you haven't yet found it http://members.dslextreme.com/users/bikecliff/
A bit of history or pictures might help us help you.

[justinsrad98]

We did change the regulator and rectifier today and the main fuse keep blowing. We check the voltage and here are the reading

idle : it jump from 11 to 19 every 2-3 secs
4000 rpm : 14 volts

I did notice the coil is aftermarket ( accel)

I bypass the main fuse with a jumper wire and the fuse on my jumper wire kept blowing after 4-5 minutes.

any clue?

[Brendan W]

Take out the lights and signal fuses and run the bike with the regulator output disconnected.
What did you replace the regulator and rectifier with ?

[JTGS850GL]

Start off with not jumping out the fuse with wire. You could end up with a whopper of a short in your main harness. Like Brendan said... Start by disconnecting things until the problem goes away.

One question though... Does the fuse blow with the ignition on but the engine not running?

[AndrewinVictoria]

Try buffing the fuse holder tabs with a wire dremmel tool. Mine stopped heating up and blowing after that.

[justinsrad98]

Start off with not jumping out the fuse with wire. You could end up with a whopper of a short in your main harness. Like Brendan said... Start by disconnecting things until the problem goes away.

One question though... Does the fuse blow with the ignition on but the engine not running?

It blow with the Engine running after 3-5 minutes. Is it possible the aftermarket coil is taking to much amperage?

[argonsagas]

Two things....

1...you should NEVER see a voltage reading of 19 volts.

2-...getting that reading consistently is a guarantee that there is something amiss with the charging system and it will cause harm

[posplayr]

Two things....

1...you should NEVER see a voltage reading of 19 volts.

2-...getting that reading consistently is a guarantee that there is something amiss with the charging system and it will cause harm

19v with new regulator and a rectifier ? This is going to be a long thread.

[justinsrad98]

Did a couple test yesterday.

Stator unplug
Regulator/ Rectifier unplug
Light fuse removed
CDI and Coil fuse still on the bike
battery charger on the battery to have enought power

bike run fine for 5 minutes then fuse blow. engine die.
then with the engine not running, a couple second later, I remplaced the fuse and it blow right away. waited 10 minutes, put new fuse and it started again....


then 5 minutes later fuse blow!!!!!

I'm clueless now!

[Brendan W]

Did a couple test yesterday.

Stator unplug
Regulator/ Rectifier unplug
Light fuse removed
CDI and Coil fuse still on the bike
battery charger on the battery to have enought power

bike run fine for 5 minutes then fuse blow. engine die.
then with the engine not running, a couple second later, I remplaced the fuse and it blow right away. waited 10 minutes, put new fuse and it started again....


then 5 minutes later fuse blow!!!!!

I'm clueless now!

Not quite. You are quite a bit further down the road of catching this thing.
It's not the regulator , not the lights, not the stator.
Just to be clear, did you run the bike with only main and ignition fuses ?
You probably have a short somewhere. The red feed from the battery goes through the main fuse and forward to the ignition switch plug in the head light bucket. Check that red feed in the fusebox tail as far forward as you can and check the arrival at the ign switch plug in the headlight. The main feed comes back orange from the ignition switch to the fusebox. Again check that orange wire at the headlight bucket plug and the return at the fusebox tail. As the main is blowing I would suspect that the problem is somewhere on that red to orange loop from the fusebox tail and back again.
The ign feed is orange and white. It goes forward from the fusebox to the kill switch, starter button, coils and back to the ignitor. I would target the wiring at the coil supply plugs first especially as they have been replaced and it's a prime spot for POs to display their wiring skills.

[justinsrad98]

Not quite. You are quite a bit further down the road of catching this thing.
It's not the regulator , not the lights, not the stator.
Just to be clear, did you run the bike with only main and ignition fuses ?
You probably have a short somewhere. The red feed from the battery goes through the main fuse and forward to the ignition switch plug in the head light bucket. Check that red feed in the fusebox tail as far forward as you can and check the arrival at the ign switch plug in the headlight. The main feed comes back orange from the ignition switch to the fusebox. Again check that orange wire at the headlight bucket plug and the return at the fusebox tail. As the main is blowing I would suspect that the problem is somewhere on that red to orange loop from the fusebox tail and back again.
The ign feed is orange and white. It goes forward from the fusebox to the kill switch, starter button, coils and back to the ignitor. I would target the wiring at the coil supply plugs first especially as they have been replaced and it's a prime spot for POs to display their wiring skills.

what do you mean by : it's a prime spot for POs to display their wiring skills???

I alreaddy bypass the red wire. I use a wire from the battery with a 15 amp fuse and I connected the wire to the orange wire to the fuse box to feed the coil and cdi and light. I will investigate that orange wire a little bit more today.

[Brendan W]

what do you mean by : it's a prime spot for POs to display their wiring skills???

Some will hack into the original harness and use cheap connectors or twist wires together or solder wires into the back of the original plugs leaving solder whiskers or bare wire exposed and then stuff the plugs back into the frame.

[justinsrad98]

Some will hack into the original harness and use cheap connectors or twist wires together or solder wires into the back of the original plugs leaving solder whiskers or bare wire exposed and then stuff the plugs back into the frame.

pretty much how the bike wiring is! The problem is that I work on a friends bike and time is limited!!! I guess I will have to redo everything!

[Steve]

What is the capacity of the fuse that keeps blowing?

You said you have bypassed the main fuse with a wire and another fuse. Still between the battery and the ignition switch?

Does the bike have to be running to blow the fuse, or just have the key turned ON?

Your voltage spiking to 19 is something that has to be addressed, too. If you KNOW it's a good R/R that you installed, check the wiring on it. The three input wires should be connected directly to the three wires from the stator. The output wire should be connected to the red lead on the left side, between the battery and the airbox. The ground wire needs to be grounded. Next question is "WHERE is it grounded?" If it is attached to its usual spot, somewhere on the panel on the left side of the battery, make sure there is another wire that goes from that same bolt to a good ground on the frame or directly to the battery. If the voltage still spikes, you have R/R issues and need another one. Best to source an SH775 from a Polaris and have a little peace of mind.

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