Main Fuse Continually Blowing

[JamesH]

Greetings all, this is my first post on your forum. So first of all, Hello everyone!
The bike in question is a 1978 (I believe) GS650. The bike is not mine. It belongs to a friend who is not mechanically savvy, and I have a few bikes including late 70's kz900 and 1000s which I am always working on, so i offered to work on his bike for muuuch less than any bike shop in town would.
So here is my current (and first to try and sort out) issue with this bike: Upon driving it to my house via the back of my truck and unloading it, I turned the key and got no response whatsoever. (At the owners house the key turning at least made the neutral light turn on). This I saw was due to a blown main and ignition fuse. I replaced the fuses and tried again with the same result. As of now, within 2 seconds of turning the key to the 'on' position, the main fuse blows. I stand there and watch it burn up!

This seems to be the result of a massive short in the main circuit, but so far i have not been able to find anything. The back of the fusebox appears to be in fine shape. I am replacing the fuses with the correct amperage fuses. Ive been in the headlight and everything seems alright. I have a wiring harness diagram and have basically traced everything possible. Has anyone experienced a similar problem? Could this be a result of a bad ignition switch? Any input would be appreciated!

-James

[tkent02]

1n 1978 there were no GS 650s, and the 550 and 750 bikes only had one fuse.
Probably best to start with IDing the year and model.
If you have multiple fuses, pull them all, put in the main fuse, does it still blow?

Better idea, break out the multimeter and start testing the circuits.

[trippivot]

here is how you find the problem.

is the fuel tank pinching the main harness?

there is a big power wire hitting a ground.

The way to isolate a SHORT CIRCUIT is to put a light bulb hooked across where the fuse would go.

I have alligator clips on test wires and a spare turn signal. 1 lead wire hooked to one end of the fuse holder to one connection of the test bulb. the other end of the fuse holder to the other lead of the test bulb. SHORT CIRCUIT will make the light bulb light VERY BRIGHT. now as the bulb is lit BRIGHT start pulling twisting and looking everywhere for the bare wire shorting out.

if the bulb is shining BRIGHT you have a short and will pop a fuse.
if the bulb is off you still have a problem - just no power. keep looking.
What you are looking for is a VERY DIM illumination of the test bulb..

when the test bulb is DIM you may replace the fuse and the circuit is restored to normal.

[Planecrazy]

Welcome to the forum, James!

I have a 1982 GS1100GK that does exactly the same thing. The prior owner told me he had been riding the bike regularly until one day when it stranded him at work. I haven't had a chance to do any diagnostics on this bike, but when I unplugged the stator / R/R from the system I was able to start and run the bike without any problem, and all the other electrical components appear to be working. Obviously the bike will only run as long as the battery is in a good state of charge, but at least I was able to tell that the bike was in good mechanical shape overall.

I still don't know whether I have a bad R/R, a bad stator, or both (because this was bought spur of the moment and isn't my rider) but I figured my experience might help you narrow down the source of the trouble with your bike. If the bike runs with the charging system disconnected, you can then run through "The Stator Papers" to further narrow down which component has failed. The Stator and R/R systems are notorious troublemakers on the GS's, so I wouldn't be surprised if that's where the problem is.

There are far more experienced problem solvers on the forum who will, no doubt, be along shortly to provide more assistance if you need it.

Regards,

[BassCliff]

Greetings and Salutations!!

Hi Mr. JamesH,

I can't add much to the great advice already given, so I'll just do my "welcome thang".

But I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", the Carb Rebuild Series, and the Stator Papers. Now let me roll out the welcome mat for you...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[tom203]

1n 1978 there were no GS 650s, and the 550 and 750 bikes only had one fuse.
Probably best to start with IDing the year and model.
If you have multiple fuses, pull them all, put in the main fuse, does it still blow?

Yes, the correct model would be nice info.
Anyways,as stated, just try the main fuse with ignition fuse out. You could be grounding out in multiple places- this is the place to start! Let us know. main fuse 15amp. The rectifier/regulator output connects to this fuse- no matter whether key is on or off.

[Redman]

JamesH,

Welcome to GSR.

I see that Steve PlaneCrazy has already suggested what I was going to say. ANd that is to disconnect the R/R, and see if the fuses don't blow. If fuses dont blow, then the R/R is the likley suspect. With the R/R disconnected can run bike some (you have a battery charger?) to work on other things.

The R/R will be the aluminum thing with heat fins, maybe on bottom of battery box or maybe on side of battery box. (I had 650G for 20+ years, but dont specifically remember, didnt have to do much work on it at all.)

Where are you located?

Maybe you can find the metal tag on sterring neck, should have a date of manufacture there.

650's came out in 81, but I havent seen nor heard of many 81's (in US anyway), have known of more 82 and on.

.

[BadBillyB]

I do the exact thing Trippivot does, but I use an old sealed beam headlamp. With the key on, the amperage from the short will light the bulb. Disconnect and reconnect things one at a time until the lamp goes out. When it does go out you have found the circuit that has the short in it. Narrows it down a lot....Billy

[1_v8_merc]

JamesH,

650's came out in 81, but I havent seen nor heard of many 81's (in US anyway), have known of more 82 and on.

.

Hmmm.... never knew they were so rare.

Because suzuki apparently used some 81 motors in the 82's.
It could have been just the Heads if not the motors.

Because I went to the suzuki dealer to get some Valve gasket sets, and the ones he gave me would not fit.
I took it back and said "hey this is off-set and bolt patterns are different."

We triple checked the serial number/part number...it WAS the correct gasket for my bike, but did NOT fit.....

We looked into the computer system more, and he managed to find an Old serial number for the valve gasket that was no longer produced for the 82 650.
He compared it to the 81 650 and it was a match.

He went on to say that apparently Suzuki had changed the Upper Head/Valve shape slightly after 81. But ended up using some left overs and dumping them on the 82's also.

So some 82's actually have the 81 motors or Just the 81 cylinder head styles.
(cant remember if it's the motor or heads....sorry)

I actually made a Thread about it earlier this year I believe.

But yeah....I NEVER DID get the correct valve gasket for my 650!
I just did a little cut and paste and made her fit with a little RTV, .

[tom203]

Hmmm.... never knew they were so rare.



But yeah....I NEVER DID get the correct valve gasket for my 650!
I just did a little cut and paste and made her fit with a little RTV, .

Rare ? I test rode a gs650 in N.H. in fall 1981- that test ride " prompted" me to find one 27 years later!
Anyways, yes suzuki changed the head slightly during 82 for some reason and you have to be careful buying the cam cover gasket.
This poster ( JamesH ) said the fuse blows when he turns key on, not when it's off, so r/r wiring escapes immediate blame since it's always connected to main fuse and would blow before he moved key to on. He needs to get a deluxe Basscliff wiring diagram for whatever bike this is.

[JamesH]

Thanks all for the replies...I will probably start messing around with this tomorrow. Ill try taking out the ignition fuse and see if the main fuse still blows, then the R/R. Bike is an 82. I have done continuity tests on many wires, but was out of town for a month and do not remember which ones were bad. I'll do that tomorrow as well.

[salty_monk]

Check that the kill switch wires are not pinched in the right side housing... I had that issue with similar result.

Dan

[JamesH]

Spent a few minutes with it today...

And the problem was narrowed down...The main fuse does not blow when the ignition fuse is pulled...So there is an issue in my ignition circuit. Will continue to investigate tomorrow...Any input welcomed!

[Redman]

....
....This poster ( JamesH ) said the fuse blows when he turns key on, not when it's off, so r/r wiring escapes immediate blame since it's always connected to main fuse and would blow before he moved key to on. ......

Oh, yah, okay, that is correct.

.

[Redman]

And the problem was narrowed down...The main fuse does not blow when the ignition fuse is pulled...So there is an issue in my ignition circuit. Will continue to investigate tomorrow...Any input welcomed!

Good that you have narrowed it down, dispite the not completly acurate advise (mine).

Assuming the 650 is like most other GS's; The ignition fuse circuit is like this:
The orange/white wire goes from the fuse box to the kill switch,
and goes thru that (if on) and comes out as an other orange/white wire which goes to all of the following:
- starter button
- one ignition coil
- other ignition coil
- ignitor unit, and ignition signal pickup unit goes to ignitor unit.

So, I would say to rig up a light in place of the ignition fuse as described in other postings (that works, I have done that myself, learnt that trick from an old electricain when I was first out of school).

Or use this techique:
(get more fuses)
. unplug both coils (easy to find after removing gas tank)
. unplug the ignitor unit (ah, I dont remeber where that is on 650, never had to work much on the 650 I had))
. unplug the ignition signal pickup
. turn the kill switch to off
. replace the fuse and turn on ignition. if fuse doesnt blow then know wiring is good up to the kill swtich.
. turn kill switch to run. if fuse blows then maybe be aproblem inside the starter button or somewhere in the wiring harnes. if fuse doesnt blow, then might wigle around the connectors that were disconnectged, if fuse still doesn blow then can say the ignition wiring harnes is okay and must be one of the devices (that are unplugged) must be the problem.
. plug back in ....one at a time.... the coil, the other coil the ignitor and then the signal generator to see which device it is that is blowing fuses.

>>>>>>>>>later note.
Here is link it BassCliff BikeCliff website 650 scheamatics.

http://members.dslextreme.com/users/bikecliff/images/gs650wiring.html

Yep, ignition circuit is like I described.

Hey, wait a minute .....
You havent posted a picture of your bike yet.
.