Help 1986 Sportster EVO sputtering/lurching
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From: Boston
Help 1986 Sportster EVO sputtering/lurching
Hello,
Took a ride down to Cape Cod on a Hot day. Bike ran like a top whole way down, Then after accidentally starting out in 2nd gear after getting off highway, bike starts sputtering in fourth gear. Bike rode crappy for the rest of day, even after changing plugs. Runs good in 3000rpm range. idles fine. only under load it sputters/lurches/backfires. Ran pretty good whole way home. Seems to be in sweet spot @ 3200 rpm, so i think timing is ok. I think this is electrical and not fuel. I read coil can go bad due to high heat. (it looks like original coil on there)
Also, hesitatates under load, (you can watch tach dip down intermittently)
Does this sound like a bad coil or bad points? or open to any and all suggestions.
Tx in advance!
Took a ride down to Cape Cod on a Hot day. Bike ran like a top whole way down, Then after accidentally starting out in 2nd gear after getting off highway, bike starts sputtering in fourth gear. Bike rode crappy for the rest of day, even after changing plugs. Runs good in 3000rpm range. idles fine. only under load it sputters/lurches/backfires. Ran pretty good whole way home. Seems to be in sweet spot @ 3200 rpm, so i think timing is ok. I think this is electrical and not fuel. I read coil can go bad due to high heat. (it looks like original coil on there)
Also, hesitatates under load, (you can watch tach dip down intermittently)
Does this sound like a bad coil or bad points? or open to any and all suggestions.
Tx in advance!
Last edited by mdoher1; Jul 8, 2011 at 03:47 AM.
Seasoned HDF Member
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From: Coromandel Peninsula New Zealand
Look under the battery box where the 3-wires from the ign pick up are routed. They rub on there and eventually short and cause a misfire. Can also do it where the wires go under the starter.
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From: Boston
Good thinkin' !! I did see a small wire up against cylinder head and thought about that. but it looked ok.
Could starter negative ground cable cause misfire? that one the insulation is compromised, but i figured, hey its just a ground cable.
Could starter negative ground cable cause misfire? that one the insulation is compromised, but i figured, hey its just a ground cable.
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From: Bluffton, South Carolina
Rule out all weird stuff by checking all connections, ground and hot along with the insulation on all the wires. On a sporty this isn't that hard. Keep us informed, hope this helps.
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From: NW AR
If the tach drops down when it's missing, then it is an ignition system problem, and most likely on the primary side, not the high voltage side. Does it do it only when hot? Or any time? Hopefully you don't have points. It does sound like a wiring problem, like a poor connection that is vibrating at a certain motor speed. Try having the bike idle and (carefully, so you don't burn yourself) wiggle wires in the ignition system and see if it dies. In particular, the wires from the cone sensor (not points) going back, as descibed above, to the module under the cover on the left side, and the wires going from there to the coil. It could also be a +12 to the coil problem, which comes through the handlebar kill switch, if I recall. Anyway, wiggle and tug on wires and see if it will die or if the ends come off.
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From: Coromandel Peninsula New Zealand
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From: Boston
The wires all look ok. I will do the wire wiggle testing tomorrow
The air down the cape was thick. You could cut the air with a knife.
"Does it do it only when hot? Or any time? Hopefully you don't have points" A: Very next morning started up and backfired, and snap krackle popped all through first gear (while cold).
The air down the cape was thick. You could cut the air with a knife.
"Does it do it only when hot? Or any time? Hopefully you don't have points" A: Very next morning started up and backfired, and snap krackle popped all through first gear (while cold).
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From: Boston
"Did the tach just drop down with the motor speed or did it really drop a lot? That is, you're at 2000. Cough, sputter, tach says 1900 or tach says 0 or 500?"
A: Drops with motor speed (as surging), (just a little bit) like 1900rpm...
A: Drops with motor speed (as surging), (just a little bit) like 1900rpm...