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Help ZXR250C coil wiring, and an unwanted inline 3 conversion

Discussion in 'Kawasaki 250cc In-line 4's' started by Golubov, Dec 29, 2023.

  1. Golubov

    Golubov Across the universe Premium Member

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    Dear Gents,

    I'm putting together my 1992 ZXR250C after a rebuild. (Crankshaft sprocket lost a couple of teeth and dropped the chain. Second-hand crank installed, with its own conrords, new piston rings and new cam chain.) What I'm struggling with:
    The bike starts, but cylinder 2 doesn't fire. Or doesn't always. A clean plug turns black, when removing the plug cap while running makes no difference. Spraying brake cleaner into the intake stalls the bike on all cylinders, except on cylinder 2 it makes no difference.
    -Pickup coil measures within spec
    -Ignition coils also measure within spec, but on the higher end of tolerance.
    -Plug caps are 5kOhm NGKs, it has worked before with no issue
    -Inspected and replaced spark plug leads where necessary (cyl 2 was actually good)
    -When the battery runs low, I lose spark completely. (Low means between 12-12,3V)

    I suspect I might have (also) messed up the coil wirings. Can somebody please check if I got the red/black/green wires hooked up correctly? Thanks! :)

    Greetings from Austria
    IMG_2626.jpeg
     
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    Golubov, Dec 29, 2023
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  2. Why?

    Why? Active Member Premium Member

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    Red and Green wires go to coil of cylinders 2&3, red and black wires go to coil of cylinders 1 & 4
     
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    Why?, Dec 29, 2023
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  3. Golubov

    Golubov Across the universe Premium Member

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    That part is clear, but the coils have a black and a green header. Which cable goes where? :)
     
    Golubov, Dec 29, 2023
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  4. gregt

    gregt Well-Known Member Premium Member

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    The general convention with coils is that the green should go to the larger of the coil terminals - if there's a size difference.
    If they are the same size it shouldn't matter.
    Pull the cap off the #2 lead, turn the motor over on the starter and see if there is a spark from that lead to an earth point.

    I'd point out that with twin lead coils, if one side sparks then the current is getting back to the other side of the coil somehow.
    Often by a leaky lead - which may be seen in the dark.
     
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    gregt, Dec 29, 2023
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  5. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Often if you look at the spade connectors for coils, one will be marked positive.

    The plug leads can either be numbered, or their length will give you an indication as to which cylinder they belong to.

    If the spark plug on #2 is black and wet, likely issue is fuel supply. On many Keihin carbs, the issue will be the float seat o-ring having perished, you will get fuel leaking past the seat - so no control of fuel supply. It may not flood the carb due to having a vacuum fuel tap, so the issue will only be present when the engine is running, or if the diaphragm in the fuel tap has failed and it's gravity feeding (or on the prime setting)
     
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    Linkin, Dec 29, 2023
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  6. Golubov

    Golubov Across the universe Premium Member

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    Funny thing is: all the leads have good spark when the battery is charged properly. Also checked lead #2 several times. When it didn't have spark, neither did the others.

    As for the connectors, they are the same size. They have no + and - markings, both have the same green and black connectors.

    I verified the leads and where they go according to the manual, we should be good there.
    The carb I'm using has needles and jets from a keyster fuel tuning kit, but I think I didn't replace the float valves and seats, or the O rings around them. Luckily I have a spare carb that I assembled with the original needles and jets, + new float valves + O rings, so I can test with that. Problem is, now this damn thing won't even start. After I drained the battery to a point where I had no spark again, I decided to call it a day.

    So in conclusion: does it even matter how the coil wires (not the plug leads) are hooked up? I remember reading that on suzukis if you hook them up the wrong way, you'll have weak spark. Also now I connected them according to the manual, but looking at my photos I had it hooked up the other way around before - and it worked.
     
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    Golubov, Dec 29, 2023
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  7. Golubov

    Golubov Across the universe Premium Member

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    Well, it works. It was a carb problem after all.
     
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    Golubov, Jan 2, 2024
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