89 FLHS ignition?
Seasoned HDF Member
Joined: Aug 2007
Posts: 8,202
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From: NW AR
Do you have a tach? If the tach is stable, then it's the carb. If no tach, you can get a little pen like device that will flash when held next to a firing plug wire. Gets a little complicated holding the device next to the wire with the button on while you accelerate to make it miss, but it's possible.
Seasoned HDF Member
Joined: Aug 2007
Posts: 8,202
Likes: 3,089
From: NW AR
If the tach is stable, it is still possible that the plug wire is shorting to ground or the plug is fouled. To check the plug wire, grab it while it's running. If it throws you across the garage, it's bad. I believe there may be other tests for that too, but somehow that one always seems to be used. New plugs never hurt. However, a tach signal means that the ignition module, pickup, ignition wiring, etc. are OK.
Cruiser
Joined: Aug 2008
Posts: 159
Likes: 1
If the tach is stable, it is still possible that the plug wire is shorting to ground or the plug is fouled. To check the plug wire, grab it while it's running. If it throws you across the garage, it's bad. I believe there may be other tests for that too, but somehow that one always seems to be used. New plugs never hurt. However, a tach signal means that the ignition module, pickup, ignition wiring, etc. are OK.
Seasoned HDF Member
Joined: May 2008
Posts: 21,216
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From: South Carolina
The best method is to get someone else to grab the plug wires...
Outstanding HDF Member
Joined: Oct 2010
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From: Near Frankenmuth, MI
The list is long.
If your lucky it may be just loose or corroded connections on the battery.
Ignition module, cam sensor, coil and the ignition circuit breaker.
Also fuel line, tank vent, plugged tank filter. And even bad gas.
Uncertain if you have EFI or carb? Carb could have a float bowl issue starving the gas flow.
And to add to the aggravation it could be an ignition module that works correctly only part of the time.
I had that issue and discovered it got progressively worse. The real issue was that if you shut off the bike and restart it it worked again for a while. I discovered you had to leave the ignition on when the bike faltered and test for spark without shutting off the key and turning it back on.
If you discover it's the ignition module you may want to upgrade to one a lot more programmable to improve your performance ... just by changing the module.
And last would be corroded contacts, broken or damaged secondary wiring.
Good Luck.
If your lucky it may be just loose or corroded connections on the battery.
Ignition module, cam sensor, coil and the ignition circuit breaker.
Also fuel line, tank vent, plugged tank filter. And even bad gas.
Uncertain if you have EFI or carb? Carb could have a float bowl issue starving the gas flow.
And to add to the aggravation it could be an ignition module that works correctly only part of the time.
I had that issue and discovered it got progressively worse. The real issue was that if you shut off the bike and restart it it worked again for a while. I discovered you had to leave the ignition on when the bike faltered and test for spark without shutting off the key and turning it back on.
If you discover it's the ignition module you may want to upgrade to one a lot more programmable to improve your performance ... just by changing the module.
And last would be corroded contacts, broken or damaged secondary wiring.
Good Luck.
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