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  1. #1
    I transcend race Hombre! TBone14's Avatar
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    94 SL750 - no fire in Mag Cyl

    Hey guys...just wanted to check thoughts on this:

    I have a 94 SL750 with good compression.

    I rebuilt the carbs, added a 3-outlet fuel pump, 780 reeds/spacers, replaced all fuel lines and filters, replaced oil lines and filters.

    The mag cylinder isn't firing. I checked stator resistances and all are to spec, I checked coil resistance and all are to spec. I haven't checked for spark yet using K447's method in the video, but that is next. If no spark I'm assuming CDI, is there anything fuel related that could cause this?

    What am I not thinking of?


  2. #2
    stubburnjdh's Avatar
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    Try the method in the video. I used it to find out my mag cylinder was not firing (fouled plug). Did you trim your plug wires back also??

  3. #3
    I transcend race Hombre! TBone14's Avatar
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    Yeah, forgot to mention that...trimmed plug wires and put in new plugs.

    Quote Originally Posted by stubburnjdh View Post
    Try the method in the video. I used it to find out my mag cylinder was not firing (fouled plug). Did you trim your plug wires back also??

  4. #4
    stubburnjdh's Avatar
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    I would try the video method and check if it is a electrical or fuel problem on that cylinder. Basically take a known good plug and wire from another cylinder and put it on your dead cylinder. It runs quit well on just one cylinder. Test the bad cylinders wire on a running cylinder and see if it fires. Just make sure you ground the other wires.

  5. #5
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by TBone14 View Post
    ...The mag cylinder isn't firing. I checked stator resistances and all are to spec, I checked coil resistance and all are to spec.

    I haven't checked for spark yet using K447's method in the video, but that is next.

    If no spark I'm assuming CDI, is there anything fuel related that could cause this?

    What am I not thinking of?
    That would be Randy's method

    Unlikely to be the CDI, as all three spark plugs on a normal Fuji engine fire together, every time.

    You can simply swap MAG and CEN plug wires, as all spark plugs fire together. See if the problem stays with the MAG cylinder, in which case it is not ignition.

  6. #6
    I transcend race Hombre! TBone14's Avatar
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    Quote Originally Posted by K447 View Post
    That would be Randy's method

    Unlikely to be the CDI, as all three spark plugs on a normal Fuji engine fire together, every time.

    You can simply swap MAG and CEN plug wires, as all spark plugs fire together. See if the problem stays with the MAG cylinder, in which case it is not ignition.
    Good point..

  7. #7
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Ohm test the coils?

  8. #8
    I transcend race Hombre! TBone14's Avatar
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    Yeah I ohm tested the coils. I re-trimmed the plug wires and it ran on all three. I revved it up a couple of times - on the second rev it backfired....maybe flooded a bit from not running right? All electrical tested fine, all new fuel stuff - maybe the timing is off? I am gonna drop it in and see how it goes

  9. #9
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Backfired out the carb or waterbox?

  10. #10
    I transcend race Hombre! TBone14's Avatar
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    Waterbox

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