80 flt back fire
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Stage I
Joined: Jun 2016
Posts: 1
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From: wis
80 flt back fire
i own a 1980 flt, basically stock, ss super e, 32 amp stator etc, ran like a champ for years. suddenly , on way to work it would pop out exhaust once or twice, then smooth again. got a little more frequent, changed plugs, cleaned carb, new intake bands, no change. i dont mean a little pop either, a gun shot bang, usually twice,loud. not its often enough i cant take it out. kind of stumped, buddy thinks a exhaust valve hanging up, but hate to pull it apart if that aint it. any help would be great.
Seasoned HDF Member
Joined: Nov 2010
Posts: 17,548
Likes: 7,197
From: Oxford, Nc
Welcome to the forum. Does it have the original electronic ignition or points? The early electronic units would misfire frequently and the smart guys installed aftermarket systems (I liked the Dyna S personally.)
Road Captain
Joined: Jun 2010
Posts: 533
Likes: 57
From: Fredericksburg, VA
I ran a Dyna S in mine for years without issue.
If the exhaust pipes are tight and the intake bands are good, I'd probably look at ignition as well... Especially if it was running fine without changing any settings.
If the exhaust pipes are tight and the intake bands are good, I'd probably look at ignition as well... Especially if it was running fine without changing any settings.
6th Gear
Joined: Dec 2014
Posts: 13
Likes: 5
From: Rock Island, IL 61201
Does it still have the manual advance unit in it, below the points plate?
They tend to blow up, causing all kinds of popping!
They tend to blow up, causing all kinds of popping!
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Road Warrior
Joined: Jul 2016
Posts: 1,370
Likes: 439
From: va
I have had this same problem -- on 81 sportster -- a bad battery!!! , after being on a charger all winter the settlement in the bottom of the battery sloshed around early in the season ( turns & stops ) to short out a plate -- bike would Buck from the miss and straighten out until next bump , turn ect , -- LOW battery AMPS for elect. ignition
At 36 years old you could also be " losing it's ground " as the ignition is mounted in aluminum or chrome and both are poor conductors of current in this case GROUND and gaskets and oil and corrosion
Try as I did to remedy all of this , run 2 14ga wire through the wire hole for ignition put eyelet on each wire remove 1 of the mounting screws for the ignition 1 at a time and put the eyelet under screw then do the other without moving the ignition plate , run the other end of the 2 wires to the battery ground -- the PERFECT ground . I also ran 4ga wire to the starter mounting bolt and another to the frame To bring back your ground
And still it could be a bad ignition
I have a 80 FLT and 81 Sportster and they both need a little extra cleaning up of elect ends and mounting
At 36 years old you could also be " losing it's ground " as the ignition is mounted in aluminum or chrome and both are poor conductors of current in this case GROUND and gaskets and oil and corrosion
Try as I did to remedy all of this , run 2 14ga wire through the wire hole for ignition put eyelet on each wire remove 1 of the mounting screws for the ignition 1 at a time and put the eyelet under screw then do the other without moving the ignition plate , run the other end of the 2 wires to the battery ground -- the PERFECT ground . I also ran 4ga wire to the starter mounting bolt and another to the frame To bring back your ground
And still it could be a bad ignition
I have a 80 FLT and 81 Sportster and they both need a little extra cleaning up of elect ends and mounting
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Cruiser
Joined: Apr 2013
Posts: 115
Likes: 2
From: ca
I had a 80 FLT pick up from a H-D engineer in 81 with new 81 heads. they had shorter valve glides. the 80 exh . when hot used to hang up and stick . gas at that time was also getting bad with no lube in it for valves. put a can of top end lube in your gas to see if it works . Or you have a ign. / circuit breaker trouble. i had my FLT for 17 yrs. 70-80k mil's never had a valve hang up .
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Oct 12, 2017 06:28 AM