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PostPosted: Sun Apr 05, 2020 1:24 pm 
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On the street

Joined: Sun Mar 29, 2020 8:42 pm
Posts: 10
Location: Birmingham, AL
Country: United States
Suzuki 2-Strokes: 1972 GT550 & 1973 GT550
I've got a black/white wire "grounded" to the negative terminal lead that I'm not sure is supposed to be there. Wiring diagrams show this is the headlight/taillight circuit. The bike had a wind screen fitted to it so my guess is something shorted out on the custom wiring for the headlight on the wind screen. This one wire is fried pretty much all the way through the main harness.

I've got a different negative battery lead I wanted to replace this old corroded one with and since I'm going to have to repair/replace this splice anyway, can I just ground it to the frame instead of splice it into the lead or is there a specific reason why it was spliced in?

There are two black/white wires crimped on the same ring terminal and grounded to the frame just in front of the battery holder under the seat. I'm thinking of doing the same ring terminal setup on this one wire and grounding it to another frame bolt.


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PostPosted: Mon Apr 06, 2020 2:52 pm 
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To the on ramp

Joined: Sat Sep 05, 2015 3:14 pm
Posts: 251
Location: southeast pa
Country: us
Suzuki 2-Strokes: GT
I think the 550 has 2 wires on the neg. term, one heavier wire goes to the engine,(this one is for the starter motor load since the engine has rubber mounts and isolates from the frame) another lighter one goes to the frame for the rest of the electrics. I think black and white is common for grounds on these bikes.
If the black and white wire in the main harness is burnt you may need to look into this at some point. It could be the starter motor ground failed and sent the heavy load back another lighter ground wire.

_________________
76 GT185
77 GT250
77 GT380
76 GT500
73 GT550
73 GT750
74 GT750
71 T250 scrambler
75 T500 cafe


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PostPosted: Tue Apr 07, 2020 3:10 pm 
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On the street

Joined: Sun Mar 29, 2020 8:42 pm
Posts: 10
Location: Birmingham, AL
Country: United States
Suzuki 2-Strokes: 1972 GT550 & 1973 GT550
Thanks karl, that makes sense. Really need to get the wind screen off this bike to take a look at the whole harness front to back.

Does anyone happen to know the wire gauges on this bike? Looks something like 16 for most of the smaller wires and 6 or 8 for the battery leads. I'm going to either make my own or have a local auto store make the heavier battery leads for me


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PostPosted: Wed Apr 08, 2020 5:24 am 
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To the on ramp

Joined: Fri Aug 11, 2017 7:09 am
Posts: 453
Country: england
Suzuki 2-Strokes: several gt250 ramairs
hi lymbic, as has been said, all black/white wires on the gt's are earth [ground] wires. when i rebuild my harnesses now i use the new wire, which easily carries 16.5 amps, but is very thin and looks a lot thinner than normal gt wire. try it yourself. strip all the sheathing off and start at one end and work to the other. black/white wire being burnt, i'd have said it had been connected to live at some time in its life. give it a go, you'll be surprised how easy it is. the thickness of the wires depends on how much current it's got to carry, so ask for battery,starter cable for your main, heavy duty wires :D
cheers, dd.

_________________
GTS250 road registered. TS250 engine, Ramair frame.
GT250 big bang road registered. Both pistons fire the same time. USD forks.
GT285 road registered. Overbored - 58mm and TS125 +2 pistons fitted.
GT10 road registered. '65 T10 engine, GT250 frame.


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PostPosted: Wed Apr 08, 2020 7:20 am 
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On the street

Joined: Sun Mar 29, 2020 8:42 pm
Posts: 10
Location: Birmingham, AL
Country: United States
Suzuki 2-Strokes: 1972 GT550 & 1973 GT550
I peeled back some of the wire sheathing and it looks like the damage was isolated to a single black/white wire in the rear section of the harness - from the connector near the front of the seat to the battery area. I'm planning to repair it myself as you suggested dollydog - thank you.

Given everything is rated for 12 V, the starter motor is rated at 500 W (P), the alternator at 210 W, the headlamp is 50/40 W, and all of the rest (brake, indicators, etc) are rated at a maximum of 23 W. I = P / V. So, we're looking at 42 A (I) for starter, 18 A for alternator, and a max of 5 A for the rest.

For AWG, I found this chart https://www.powerstream.com/Wire_Size.htm. Looks like I could replace the black/white wire with 18 or 16 gauge, and the two terminal leads with 10 gauge.

Do you guys have a source for modern wires that match the original harness wire colors? I saw Vintage Connections stocks 10' lengths, but the current ratings seem low.


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