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 Post subject: GT 550 blowing fuses
PostPosted: Thu Apr 21, 2011 4:12 pm 
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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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 Post subject: Re: GT 550 blowing fuses
PostPosted: Thu Apr 21, 2011 7:02 pm 
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Moto GP
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Location: Mostly Barbados, sometimes Florida and western Canada
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.

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72 Suzuki GT750 cafe
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 Post subject: Re: GT 550 blowing fuses
PostPosted: Thu Apr 21, 2011 7:05 pm 
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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?

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1974 Suzuki GT550 - Smoke Generator
2010 Harley-Davidson FXDB - The Commuter
1994 Honda Nighthawk 250 - Almost Run Over


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 Post subject: Re: GT 550 blowing fuses
PostPosted: Thu Apr 21, 2011 7:23 pm 
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Moto GP
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Location: Mostly Barbados, sometimes Florida and western Canada
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.

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Two strokes, its just that simple.

The list:
69 Suzuki U70
69 Suzuki T500
72 Suzuki GT750 cafe
74 Suzuki GTXVR project
75 Suzuki RE5
75 Suzuki GT750
76 Suzuki GT750
81 Suzuki GSX1100
86 Suzuki RG500
88 Honda CR500
93 Honda CBR900RR
98 Suzuki GSF1200 X 3


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 Post subject: Re: GT 550 blowing fuses
PostPosted: Fri Apr 22, 2011 4:27 am 
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Joined: Tue Oct 21, 2008 2:41 pm
Posts: 2252
Location: Tulsa, Oklahoma
Country: USA
Bikes owned: GT550x2, GT750, GS1000
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.

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 Post subject: Re: GT 550 blowing fuses
PostPosted: Fri Apr 22, 2011 4:51 am 
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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.

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1974 Suzuki GT550 - Smoke Generator
2010 Harley-Davidson FXDB - The Commuter
1994 Honda Nighthawk 250 - Almost Run Over


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 Post subject: Re: GT 550 blowing fuses
PostPosted: Fri Apr 22, 2011 6:31 am 
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Joined: Mon Dec 13, 2010 4:32 pm
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Location: southwestern Pennsylvania
Country: USA
Bikes owned: 69 T350 thru 75 GT750
Its useful to look at the wiring diagram when sorting out your electrical problems.
http://smokeriders.com/diagrams/Suzuki/Triples/Color_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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BAS (Bike Acquisition Syndrome) - have too many bikes but still have room for one more

Suzukis:
1976 GT250
1975 GT750, GT750, GT550 & T500
1974 T500
1973 GT250
1971 T350
1969 T350
Honda: 1985 CB650SC & 1986 CB700SC
2009 Triumph Bonneville SE


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 Post subject: Re: GT 550 blowing fuses
PostPosted: Fri Apr 22, 2011 7:43 am 
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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).

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1974 Suzuki GT550 - Smoke Generator
2010 Harley-Davidson FXDB - The Commuter
1994 Honda Nighthawk 250 - Almost Run Over


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 Post subject: Re: GT 550 blowing fuses
PostPosted: Fri Apr 22, 2011 7:46 am 
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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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1974 Suzuki GT550 - Smoke Generator
2010 Harley-Davidson FXDB - The Commuter
1994 Honda Nighthawk 250 - Almost Run Over


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 Post subject: Re: GT 550 blowing fuses
PostPosted: Fri Apr 22, 2011 8:07 am 
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AMA Superbike
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Joined: Mon Dec 13, 2010 4:32 pm
Posts: 1838
Location: southwestern Pennsylvania
Country: USA
Bikes owned: 69 T350 thru 75 GT750
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) - have too many bikes but still have room for one more

Suzukis:
1976 GT250
1975 GT750, GT750, GT550 & T500
1974 T500
1973 GT250
1971 T350
1969 T350
Honda: 1985 CB650SC & 1986 CB700SC
2009 Triumph Bonneville SE


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 Post subject: Re: GT 550 blowing fuses
PostPosted: Fri Apr 22, 2011 1:23 pm 
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Moto GP
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Joined: Fri Oct 24, 2008 9:11 am
Posts: 4500
Location: Mostly Barbados, sometimes Florida and western Canada
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.

The list:
69 Suzuki U70
69 Suzuki T500
72 Suzuki GT750 cafe
74 Suzuki GTXVR project
75 Suzuki RE5
75 Suzuki GT750
76 Suzuki GT750
81 Suzuki GSX1100
86 Suzuki RG500
88 Honda CR500
93 Honda CBR900RR
98 Suzuki GSF1200 X 3


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 Post subject: Re: GT 550 blowing fuses
PostPosted: Fri Apr 22, 2011 4:50 pm 
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Joined: Mon Nov 03, 2008 10:47 am
Posts: 4939
Location: Illinois
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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 Post subject: Re: GT 550 blowing fuses
PostPosted: Fri Apr 22, 2011 5:31 pm 
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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.

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1974 Suzuki GT550 - Smoke Generator
2010 Harley-Davidson FXDB - The Commuter
1994 Honda Nighthawk 250 - Almost Run Over


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 Post subject: Re: GT 550 blowing fuses
PostPosted: Fri Apr 22, 2011 7:20 pm 
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Joined: Fri Oct 24, 2008 9:11 am
Posts: 4500
Location: Mostly Barbados, sometimes Florida and western Canada
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.

The list:
69 Suzuki U70
69 Suzuki T500
72 Suzuki GT750 cafe
74 Suzuki GTXVR project
75 Suzuki RE5
75 Suzuki GT750
76 Suzuki GT750
81 Suzuki GSX1100
86 Suzuki RG500
88 Honda CR500
93 Honda CBR900RR
98 Suzuki GSF1200 X 3


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 Post subject: Re: GT 550 blowing fuses
PostPosted: Fri Apr 22, 2011 8:07 pm 
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Joined: Wed Oct 27, 2010 6:55 am
Posts: 109
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.

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1974 Suzuki GT550 - Smoke Generator
2010 Harley-Davidson FXDB - The Commuter
1994 Honda Nighthawk 250 - Almost Run Over


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