Electrical Problems (I Just want to hear it run!!!)

[Tlamar]

I recently purchased a 1981 GS550T, that was/is not running. I have the bike hooked up to a lawn mower battery and a charger, and a plastic gas tank we use on tractors.

I can let the bike sit for about 45min to an hour, and it will start and run on all 4 cylinders for about 30 seconds to a minute. After which it will not run even though I have spark and fuel, If I let it sit for about an hour it will again run for about 1 min then die just like you turned off the ignition switch. I have checked the Regulator/Rectifier and found that it is bad (I get no conductivity in either direction almost like an open). I have not tested the stator mainly because I just want to see the bike run before I put to much more money into it. I tested the coils and wires and they all appear to be in good working order. I have not completed the ignitor test because the wire colors are a little bit different than what is in the Clymer book, but I’m kind of under the assumption that if I’m getting spark then the ignitor is good (But you know what they say about assumptions!). I have noticed that at very random intervals I will get no spark or where it almost looks like it is firing on all cylinders at the same time. I checked the signal generator and get about 66~67ohms on both sides which according to Clymer means that it is good. I thought at first that maybe the previous owner had messed with the camshaft timing but I checked it and its right on the money.

I was thinking that I could be getting bad power from the regulator/rectifier into the ignition system which could cause the intermittent firing. Is it possible for testing/elimination purposes to disconnect the 3 stator wires going into the rectifier and still run the bike when its hooked up to a battery and charger?

I’m going to go through all the connectors on the bike this weekend, and see if I can come up with anything else. Any advice you guys might have would be appreciated.

The wire colors I have on the Ignitor are as follows:

Black/Blue ???? Have no Idea
Black/Yellow Goes to Coil
White Goes to Coil
Brown Goes to Signal Generator
Green/White Goes to Signal Generator
Orange/White Goes to Both Coils

If some one can give me some info on which wire I should hook up to the 1 ½ V battery to test the ignitor it would be greatly appreciated.

[jbs80106]

I'm no expert...

But once the bike is running, I don't think its electricity out of the regulator that keeps 'er turning over. I think the 2 wires from the stator go straight to the motor....could be wrong though as I'm not an expert.....

[flyingace]

If it runs for a minute, it's unlikely to be ignition problems. They tend to be off/on in nature. Charging problems will not die in one minute either - that would be more of a slow death.

I don't know what arrangement you have for a gas tank, but standard GSs have a vacuum operated petcock that allows fuel into carbs only when the bike is running. If this is inoperable, or marginal, or the vacuum line isn't connected, the engine may use up what it has in the float bowls and quit. A minute is just about how long that takes.

[tkent02]

Does this "plastic gas tank we use on tractors" have a vented opening, or is it sucking a vacuum in the tank when fuel comes out?

[Tlamar]

The tank that came with the bike has several pinhole size leaks around one of the bottom seals, which I had planed on brazing when time permits. The plastic tank does have a vent on it.

That's interesting about the vacuum line on the petcock valve, I will try to fix the tank tomorrow and give it another try.

Thanks for all the advice, I really appreciate it!!!!!!

"Antique Tractors are much simpler"

[SqDancerLynn1]

A post for all newbies It will not run without thw complete airbox & filter

[Tlamar]

You guys are the best!!!! When I first got the bike it was not all put together, so I would have never thought that there had to be an airflow restriction on the carburetors, in fact its generally the first thing that gets thrown into the corner of the shop in order to make room.

After cleaning the carbs and putting the airbox on the bike it fired right up. I still need to sync the carbs, and do some fine tunning and cosmetic work but the bike runs great.
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