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Electrical Question

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Hello, any help on this would be greatly appreaciiated...I have a 90 FLHTC and the bike was running great until all of a sudden it started running rough and backfiring. First I thought is was a mechanical problem ( vacuum leak or bad gas), but what tipped me off to it being electrical is the voltmeter jumps around and somtimes my tach jumps around too. While all this is happening the bike runs really rough and has little or no power.

I checked the battery, examined wiring. The bike will run fine for a while until all of a sudden this problem occurs.

Thanks for your input!
Also changed voltage regulator-no help
 

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I was convinced I had an electrical problem last Spring with my 1999 Evo--turned out to be crud in the gas tank partially blocking the petcock filter. Like you, I became convinced that it was electrical because my tach was jumping around as the motor was missing. I can't explain the tach symptom electrically, but there wasn't anything electrical wrong. Mine would run rougher and rougher until it finally quit. I cleaned a surprising amount of crud from the tank filter and the inside of the petcock and no problems since.

Pull the petcock (drain the tank first) and check the filter. This is at least as easy to do as any electrical system checks.
 

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I know 2 guys who have 89 baggers, and both have very similar problems to yours. Occasional missing, tach and voltmeter jumping. On one bike I found a few corroded wiring connections, dropping voltage and getting hot. Once the voltage gets to about 9-10 volts at your ignition module, it starts missing. I repaired the ones I found, and now it is much, but not completely better. Over the winter I plan on going over all the wiring in the fairing. One tip off was that his would only do it with the spots on, if you turned them off, it was fine. Then as it got worse, even with just the headlight on it would do it. These bikes are getting older, and the wiring and connectors are not watertight, until 1994 when they went with the weathertite (deutsch) connectors. What I found on his bike and my own '90 mainly was the ring lugs on the circuit breakers, they would feel warm to the touch due to the voltage drops. Some I cleaned up, some had to be replaced. One way to troubleshoot, remove the fairing, without the engine running, turn everything on including brake lights, then after a few minutes, feel around for hot connections. Obviously, if you have a digital voltmeter and understand basic electrical, that would be even better.
 

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Check your ground cable under the bike. All rubber mounts have a seperate ground cable that eventially loosens or breakes because of engine vibration.
 

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Problem close to my heart.

I would have to go to the ground system of the bike....my 94 did the same thing plus once in awhile there was just a click when starting the bike hot. I cleaned up the wiring under the fairing replaced the starter relay everything was fine....for a while...I removed the battery cables and starter grounds...cut the insulation on the starter to frame ground cable and found that there was green corrison under the insulation. This was not noticable from looking at the wire or checking it with a multimeter...when it got hot it acted up. I replaced the wiring by going to Auto Source buying a 10 gauge, 48 inch battery cable cutting it to fit putting on the end terminals and shrink wrapping the connectors, much cheaper than the factory wiring. I have put on 5,000 miles trouble free. Also run a good ground from the triple tree to the frame the factory only started doing that in 96 before that they used the wiring harness grounds.~!Awesome!
 
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