surprise electrical problem (<---sarcasm)

[03svrider]

when i bought my 81 gs450l the guy i got it from gave me a forkbag with it and there was some extra fuses in it. i rode the bike a couple times with no problems but now it blew the main fuse. i put a new fuse in it, srated it back up and watched the fuse blow again. i put another fuse in it and it hel for ten minutes of idling. it hasn't blown yet but i'm leery of it happening again. i'm guessing i just go through and check/clean all the connections etc. sounds like fun huh? just thought i was finished with it with the brakes etc. if the rectifier gets too hot could that blow the fuse? it was pretty hot. the fuse blew after riding it up and down my long, bumpy driveway so i'm thinking where ever the short is it must've got jostled from the bumpy driveway and shorted against where ever it is shorting but it blew just as i was stopping on the smooth concrete when there was no movement at all. any good guesses on where i should start looking? i'm guessing just check every connection and so on..........

[Steve]

Connect a voltmeter to the battery terminals to see if the battery is being charged or not. Could be that your rectifier/regulator (r/r) is either not grounded well, or it is fried.

If that checks out OK, then check all the other connections, and also the wiring harness where it goes by the steering neck. It moves and flexes there, so could be a problem spot.


.

[mf70]

Also look under seat and under tank. My 250 had chafe on the main wiring harness at both places. The underseat point shorted and killed the r/r.

[03svrider]

i fiddled with it a little when i got home last night and the fuse only blows intermittently (<--sp?) it will blow when the bike is warm or cool. i hooked up a multimeter to the battery and it is charging. it's weird. also, it only happens when i start the bike and then it will be ok after replacing the fuse a couple times, then it will blow again. is the rectifier the vented metal thing under the left side sitting cover? it got pretty hot after running the bike for five minutes after replacing the fuse a couple times. looks like i'm pulling things off the bike again and looking at wires. maybe i'll get lucky and get it to do it by wiggling some connections or just put a bolt in place of the fuse and let the b!tch burnnnn!

[nabrams]

Yeah the R/R is bound to die if it's the original. I mentioned this to you in another post (http://www.thegsresources.com/_forum...php?t=109483):

By the way if that bike has the original R/R you will almost certainly need to replace it

On both the GS450 bikes I've restored (mine and my friend's) the R/R was letting too much juice through. If it gets above 18 volts or so it will burn the fuse. If it stays between 16 an 18 volts it will boil your battery dry after a few rides. So, did you verify what voltage it was charging at (while at 5K RPM)? It may also be spiking intermittently. Now, some R/Rs fail such that they let too little voltage through. I've actually seen both cases.

Now, if you totally disconnect the charging system and disable the headlight circuit, you should be able to ride (on a fully charged battery) for several hours before depleting the battery (I did this for several weeks till I got a replacement R/R). If the fuse doesn't blow, you'll know for sure it's an over-voltage from the charging system.

All this has been discussed in detail in other posts, so check 'em out for the full story.

The good news is that it looks like (from your other posts) you've hit almost all the typical problem areas with an old GS450, so you're almost done. Just to bolster your spirit: I had my first GS450 for seven years (I put at least 16000 miles on it during that time) and I put in only about $600 into it over that time - this is with me doing all the labor, no mechanic fees.

[03svrider]

thanks alot. looks like i'll be purchasing a r/r! if that isn't the problem i'm going to need one anyway! thanks to all who sent responses. i'll let ya know what transpires!

[03svrider]

got the new r/r in after having to cut the head off one of the bolts holding the "igniter box". everything is back together with bolt headed hardware (no more impact driver for removal!) and with a charged battery it idled for 15 minutes w/o blowing the fuse. crossing my fingers! i'm tired of working on this thing!

[nabrams]

The real test will be when you rev the bike to 5K RPM and check the voltage.
If that's OK and the fuse still blows at some point later in the ride then you've got a loose wire shorting out somewhere.