Main fuse blowing...help please??

[IronArse]

Hey folks, just a quick question, wondering does anyone know maybe what's going on?

The main fuse keeps blowing on my 1998 GSX R 750 (not a tourer I know, but we all have guilty pleasures ).
It blew first when I was about to take it out for a ride the other day, then when I replaced the fuse with the key out of the ignition it blew again.
Would this be a issue with;
i) Wiring to ignition
ii) Rectifier/Alternator

I've been rooting around for a long time now and I can't find a basic wiring fault on the cables, so I'm wondering it might be the alternator or something.

One thing was that when I had connected over the fuse terminals while the key was out (bad I know, but the fuse was out and all, didn't expect anything) after the first time it blew, there was a spark and the starter motor started to kick into life. This leads me to think it's a wiring problem around the ignition, I just can't see to find the fault.

Anyone have any thoughts on the matter or similar experience?

Anyways, as ever, thanks in advance for all help given, mucho apreciado!

Mick

[Bones667]

According to the web it's quite a common problem on the GSXR and is normally related to the rectifier. Check the wiring and connections to and from the rectifier in first instance and check for any obvious exposed wires which maybe causing bad earth. A friend of mine says not to use pattern electrical parts and always go for a genuine OEM rectifier if replacing it. If you know someone with same bike ask if you can swap the rectifier and see if it still blows a fuse..

Hope you get it sorted
Bones

[IronArse]

Hey Bones, cheers for the heads up!

Damn, you wouldn't want to hear the problems I've been having with the rectifier on my Wee-Strom the last few months. Say it ain't so haha!

I really can't find an earth fault or a fault between cables, but I took her for a good spin there now and she worked fine. Thing is she has blown 4 fuses previously, so I'll have to keep looking til I find it.

That's a good start though, thanks for the tip bud!

[TransalpJohnny]

Hi Mate
You were saying that the starter motor started turning
as soon as you've connected the battery.
That sounds like a sticky starter relay to me.
Take a 12 volt bulb...fit it between battery negative pole and
the battery negative cable...now for as long as there is a short
circuit the bulb will light up...but the fuse wont blow because the bulb
Limits the current...
Do switch the ignition on but do not push the starter button!
Then diconnect all branches of +12 volt supply until the bulb dims .
If the main fuse blows you draw a lot of current...between 20 and 30 amp...that means the resistance of your short circuit is well below 0.5 ohm...
Good luck ..johnny
I once had a faulty indicator relay blowing the fuse on a honda 750
Johnny

[Warin]

I'd check the battery voltage to see if it is being charged correctly.

More than 14.5v frys the battery.
Less than 13v while running flattens the battery.

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You could put a second fuse in - to take teh rectifier/regulator off the other fuse .. this way you 'll know one way of the other where the fuse blowing is coming from.