GT 550 blowing fuses

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jmcgill89
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GT 550 blowing fuses

Post by jmcgill89 »

My GT 550 is running really badly since I got it put back together. Today I was riding it and it was intermittently stalling end then just died. I found that it had annihilated the main fuse. I replaced the fuse and it promptly burned the new one. It has never done this before.....could I have attached something wrong when I hooked the wires back up behind the headlight?
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Suzsmokeyallan
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Re: GT 550 blowing fuses

Post by Suzsmokeyallan »

Its more than likely a wire has chafed or gotten pinched somewhere since you were riding it and then the fuse blew
For starters use your meter to check the red wire from the main fuse and up to the ignition switch socket to see if its got continuity to ground.
Two strokes, its just that simple.

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Re: GT 550 blowing fuses

Post by jmcgill89 »

There has been an issue with that fuse getting hot for some time...as the holder has pretty much melted around the fuse.

I think the problem as of now is that I haven't tightened the bolts for the headlight ears and turn signals enough, and I'm losing some continuity there.

However, I'm going to take all those wires apart again and use contact cleaner to make sure I'm working well there.

How do you test continuity to the ground for the main wire?
1974 Suzuki GT550 - Smoke Generator
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Re: GT 550 blowing fuses

Post by Suzsmokeyallan »

You set the meter so when both leads are touched together it beeps, as in the diode test position etc.
If the red wire is shorted to ground as in pinched, and you apply one lead into the red terminal of the main harness and the other to the frame and it beeps you have a short to ground in that wire.
Keep in mind the wire has to be isolated, such as having no other connections made to it anywhere in its circuit.
Two strokes, its just that simple.

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Coyote
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Re: GT 550 blowing fuses

Post by Coyote »

Do yourself a favor and shuck the old fuse holder. You can get a modern blade type fuse holder at Ace hardware for around $3.00. That would elimanate a potemtial problem there.
I was born with nothing and still have most of it left.

.
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Re: GT 550 blowing fuses

Post by jmcgill89 »

I plan on getting the fuse holder changed first and foremost.

Thinking about all the things that could have gone wrong, I can only leave myself with the work I did in taking off the gauge cluster and turn signals in the front.

I have to think that something just didn't get solidly hooked up there and/or I didn't tighten the grounds well enough....as I never touched any of the other wiring on the bike.
1974 Suzuki GT550 - Smoke Generator
2010 Harley-Davidson FXDB - The Commuter
1994 Honda Nighthawk 250 - Almost Run Over
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jabcb
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Re: GT 550 blowing fuses

Post by jabcb »

Its useful to look at the wiring diagram when sorting out your electrical problems.
http://smokeriders.com/diagrams/Suzuki/ ... _GT550.gif

If you didn't solidly connect something its not likely to blow the fuse unless the connector is so loose that its in contact with something that is causing the short. Otherwise a loose connector would just result in something like gauge lighting not working.

One possibility is that you moved the wires around a bit when working on gauge cluster and now a chafed wire is grounding to something.

A good starting point is to check some resistances with fuse removed and battery disconnected.
As others said, check the resistance between ground and the red wire leading away from the fuse to the ignition switch.
Do this test with:
1) key off
2) key on and lights off (if your bike has this option)
3) key on and lights on
4) key on, lights off and kill switch set to off (if your bike has this option)
5) key on, lights on and kill switch set to off
Rotate the front end to the left and right when doing these tests. Could have an intermittent short that is affected by this motion.

Check the wiring in the region you worked on. Does anything look blackened or burned by a short? Any repairs by you or a previous owner that could have gone bad?
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jmcgill89
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Re: GT 550 blowing fuses

Post by jmcgill89 »

I just recently had all those wires apart in the headlight region, as I had to repair my gauge cluster...ironically, the cluster now does not work...the turn signal light and the high beam light don't work anymore...nor does the gear indicator.

I may have to take all that apart again. I never touched any other wire on the bike, and the only thing I took off was the gas tank.

I'm replacing the Starter clutch this weekend, so I might as well just take it all apart again and start from scratch (after I get that new fuse holder).
1974 Suzuki GT550 - Smoke Generator
2010 Harley-Davidson FXDB - The Commuter
1994 Honda Nighthawk 250 - Almost Run Over
jmcgill89
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Re: GT 550 blowing fuses

Post by jmcgill89 »

Oh, and the fuse only blew when I got above about 4500 RPMs...at idle, it's all working fine....not sure if that's relevant, but there you go.
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Re: GT 550 blowing fuses

Post by jabcb »

Looks like excessive alternator output over 4,500 rpm burned out the fuse & lights.
That points to the voltage regulator.

You can get a reasonably priced voltage regulator form Oregon Motorcycle Parts.
http://www.oregonmotorcycleparts.com/
Its a direct replacement. Just need to swap out the connector with the existing one.

I've had two rectifiers go bad. I'd replace the rectifier at the same time even if the original one was OK. Oregon Motorcycle Parts also has a direct replacement the rectifier.
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 & 75
GT380 72
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T350 69 & 71
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Suzsmokeyallan
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Re: GT 550 blowing fuses

Post by Suzsmokeyallan »

I've never had a problem with the stock fuse holders design, as long as the contacts are clean it works fine. Then again any bike I've bought used has always had one in it that the previous owner has botched up, so I always had to get a new one.

jmcgill89 you did not state the fuse blew at higher rpms in your initial post, you simply stated it blew when riding,and again when replaced.
Now a problem like that could be anything related to the electrical parts on the bike and since you removed the tank it was possible something ignition to the wiring got pinched.
If your bike is in fact overcharging, did you actually check the output voltages??? you need to be complete in your testing and observation since there are too many variables and none of us are actually near the bike to see firsthand whats really going on.
Two strokes, its just that simple.

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tz375
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Re: GT 550 blowing fuses

Post by tz375 »

Allan is right. Check the output voltage with the bike running and determine if that is a problem when you rev it up.

The lights sound more like a poor ground at the front end. You can always add a couple of additional ground leads and make sure they are going to clean metal. And make sure the battery ground is clean and sound.
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Re: GT 550 blowing fuses

Post by jmcgill89 »

To check the output voltages, do I just take a meter and check the voltage at the battery when running. I am wondering how a regulator may have failed while it sat with the battery disconnected all winter.

I may have messed up a wire when installing the tank, but aside from there, The headlight is the only place I touched wires. The wire for the main fuse looks to have been heating for some time.....it looks to have wear from heat.
1974 Suzuki GT550 - Smoke Generator
2010 Harley-Davidson FXDB - The Commuter
1994 Honda Nighthawk 250 - Almost Run Over
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Re: GT 550 blowing fuses

Post by Suzsmokeyallan »

Thank you kindly Richard,,,,,,Honestly jmcgill89, the GT bikes hardly ever overcharge simply because the system is borderline to start with. The regulator is not a strong point simply because of the way it works with its mechanical contacts within the system.
It been in the bike for nearly 40 years, so I'd say its life is well past its due date.
The regulators from Oregon Motorcycle are great 'bolt on' standalone units for the money and should be one of those 'must have' upgrades to any GT owner.
What it does is react faster and charge at a more stable rate compared to the stock unit, especially where its most critical at the engines lower rpms.

What you need to do for a charging test is to measure the voltage across the battery terminals at idle, then at 3000 rpms, and 5000 rpms. You need to hold the throttle steady for at least 15 seconds at each position to get a true reading, and use a digital volt meter for recording the measurements to the decimal value.
If your bike has a headlamp switch make sure its on during the test to 'load' the charging system.

From what youve recently said it would appear the fuse holder was suspect and the wires to it have been compromised for a long time by a high resistance condition.
This will lead to overheating in the circuit and besides melting the fuse case it also destroys the wires in that area. Its possible insulation was damaged in a section and therefore allowed a 'jump to ground' which blew the fuse.
You should supply some photos of the fuse case and its accompanied wiring, thats always good for a visual review.
Two strokes, its just that simple.

69 Suz U70
69 Suz T500
72 Suz GT750 cafe
74 Suz TS250
74 Suz GTXVR project
75 Suz RE5
75 Suz GT750
76 Suz TS400
76 Suz GT750
81 Suz GSX1100
86 Suz RG500x2
88 Hon CR500
93 Hon CBR900RR
98 Suz GSF1200x3
15 Kaw Ninja H2
jmcgill89
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Re: GT 550 blowing fuses

Post by jmcgill89 »

I will try to get some pictures on Sunday when I get back home. I will plan to replace the regulator ASAP, alongth the fuse holder area. There seemed to be signs of heat all over that red fuse wire.

How many grounds am I supposed to be seeing? I have one braided wire to the negative terminal of the battery, two black wires on bolts on either side of the battery box, and the stuff in the headlight.
1974 Suzuki GT550 - Smoke Generator
2010 Harley-Davidson FXDB - The Commuter
1994 Honda Nighthawk 250 - Almost Run Over
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