gt550 electrical

[deerstud]

Hi Everyone
Today i was riding my 1974 Gt550 down the road and it started to lose power. I thought i was running out of fuel so I switched to reserve and nothing happened. I realized I had lost electrical power. Dead- nothing zip. I took side cover off and the fused had blown and I could smell a slight burnt odor. I replaced the fuse and started bike and it ran for a couple of minutes and the rectifier started smoking and then the fuse blew. I checked the battery and several cells had no water over them. I filled the battery ( 3 years old) and replaced fuse, started bike ( this time without headlight on), it ran about 2 minutes or so then the same thing happened. Any thoughts on this? I just started riding this bike and have only put 265 miles on it but it seemd to be charging OK . Also my manual has no electrical diagram in it does anyone know where I could find the schematic? Thanks for any info you might have.

[Cliff]

If it was a dead short the fuse would blow right away so there has to be something drawing too much current. I'd start with checking/cleaning all the connections. It could be something as simple as a corroded terminal in one of the push in connectors somewhere.
Try disconnecting the retifier and running the bike. If the fuse doesn't blow, then hook it back up and trying running the bike again.
Does the charging system work? You should have around 14.5 volts at the battery at 2000 rpm.

[jabcb]

Wiring diagrams are listed under the Electrical category:
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There are some variations in wiring diagrams. Some show the fuse protecting only the battery, while others show the fuse protecting both the battery & rectifier.

If the rectifier was smoking, then it could be the problem or a short could have caused excessive rectifier current & overheated it.

To check the rectifier:
1) check the resistance between each yellow wire and ground
2) reverse the meter leads and recheck the resistance between each yellow wire and ground
You should get high readings for one test and low readings with the meter leads in the other direction
3 & 4) repeat the tests for each yellow wire & the red wire
Again, you should get high readings for one test and low readings with the meter leads in the other direction

A simple test that would be a starting point: disconnect the rectifier & voltage regulator, charge up the battery and run the bike for a while to see if you blow another fuse.

[deerstud]

I was wondering if this would be caused by a short in the battery also. I tested the charging system about a month ago and the highest reading was only 12. 67 volts. I had to run about 3000 rpms to get that. At that time there was some smoke but did not blow fuse. I found the fuse holder was coming apart so I taped it up and all seemed well until this episode. if I disconnect the rectifier I wouldn't think anything would get to the battery.

Thanks for the schematic link.

[jabcb]

We aren't suggesting that you use the bike with the rectifier disconnected. Testing without the charging system is a useful first step in diagnosing the problem.

If you still blow fuses after disconnecting the rectifier and voltage regulator, then there is a short someplace outside of the charging system. Would need to find & fix that problem before addressing any issues with the charging system.

Is the battery in good enough shape to run the starter, or do you kick start the bike?

[deerstud]

I have to kick the bike because the starter clutch is bad. If I disconnect the rectifier and regulator out of the system would I still have power elsewhere and to the ignition for starting purposes. If I had a bad cell in battery would that overheat the rectifier and blow the fuse? I do have a spare rectifier but not a regulator. Maybe I should isolate the rest of the system.

[deerstud]

I'm going to put a charger on battery now and get it charged up.

[jabcb]

Its worth doing some testing before swapping out the rectifiers. If a short damaged the rectifier, then it could also damage the new rectifier.

[deerstud]

I charged battery. I put knew fuse. I have power but now bike won't start so I'm going to have to dig further. When this all happened Sunday as soon as I replaced the fuse the bike would start so I'm not sure what's going on.