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Thread: Low Spark

  1. #1
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    Default Low Spark

    I have a 1976 FXE , fresh top end , new starter , points, condenser, coil , plug wires and plugs , and a new battery.
    Battery pushes the starter just fine , static timing has been done , push rods are adjusted correctly. I just have the starter wired and the ignition wired, nothing else . Bike turns over like a champ but will not run . Little puffs of smoke coming out of the exhaust. I pulled a plug to check for spark and it is barely throwing off any spark at all. What can be causing this ? Troubleshooting today , I hope you guys can help direct my efforts.
    Thanks

  2. #2

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    Quote Originally Posted by Joeytats View Post
    I have a 1976 FXE , fresh top end , new starter , points, condenser, coil , plug wires and plugs , and a new battery.
    Battery pushes the starter just fine , static timing has been done , push rods are adjusted correctly. I just have the starter wired and the ignition wired, nothing else . Bike turns over like a champ but will not run . Little puffs of smoke coming out of the exhaust. I pulled a plug to check for spark and it is barely throwing off any spark at all. What can be causing this ? Troubleshooting today , I hope you guys can help direct my efforts.
    Thanks
    Spark observation is pretty subjective: Try it in the dark. You should have a nice bluish spark. "Barely" spark looks like that in direct light, even if you have a good spark. Since your bike turns over fine, I doubt its a battery issue.

    Are the plugs wet with fuel?

    I would do these checks in order.

    After each one, see if you can start it and it runs (Even if you have already done these checks)

    -Fuel is on, and is going to the carb

    -Proper spark plugs? (Make/model, reach) and gap

    -Check points gap

    -Proper coil? (Points vs electonic ignition coil)

    -Disconnect the hot wire from the coil where 12v comes from the igition switch. Place a jumper wire from the battery to where you disconnected the hot wire from the coil. What you have now done is "Hotwired" the bike by bybassing the ignition swith and associated wiring in case you have an switch or wiring issue. Be sure you take this jumoer wire off when not needed as it is feeding 12v constant. So if it starts and runs, to cut off the engine, remove the bat end of the jumper wire

    -Static timing

    -Check your push rod adjusment

    -Check your compression in each cylinder/ It doesnt take much spark to ignite fuel/air

    Good luck, let us know how it turns out

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    Thanks for the check list
    Plugs are wet , went as far as pulling a plug and added gas directly to the cylinders… with spark I thought I’d get it to run for a couple seconds at least , nothing … I’m going to try the jumper

  4. #4

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    Good list above.

    I will add: weak spark at cranking speed is one symptom of a bad condenser. Lots of bad condensers and bad coils out there these days. Quality control just does not exist for these items anymore.

    Jim

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    Well heres how the day went ,
    I first tried the jumper wire that was suggested and that didn’t work. I then removed the brand new points and condenser set up and installed the old original points set up. Then did the static timing again . Tried starting it a few times and got the same results. I noticed a lot of gas coming back out of the the carb ( s&s super E w/o the air cleaner attached ) . I took a rag and stuck it in there and cleaned up the excess gas. I left the rag in my hand on the outside of the carb blocking the air and tried to start it …. Son of bitch fired right up ! Now the motor just races , idle screw is all the way out . I then removed that super E and installed an older one that was on the bike , and it was off to the races again . Turned idle screw all the way out , checked to make sure I had slack in the throttle cable …Maybe the air/fuel needs to be tuned. Open to suggestions! Lol !

  6. #6

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    Have you serviced the advance unit on this motor?

    Are you using the intake manifold o-rings that are stock and correct for this motor, or are you using the bands?

    Too much advance and/or a vacuum leak is what I am adressing.

    Jim

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    There are bands on the intake . I have O rings , you think I should switch ? Just wanna be sure that manifold is an O ring manifold

  8. #8

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    Quote Originally Posted by Joeytats View Post
    There are bands on the intake . I have O rings , you think I should switch ? Just wanna be sure that manifold is an O ring manifold
    Yes, both the head and manifold must be cut for o-rings or they won't fit. But the o-rings are as close to foolproof as you can get, as long as you have good clamps.

    Jim

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