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only 1 cylinder sparking..GSX 250

Discussion in 'Technical and Troubleshooting Torque' started by phabbo11, Jan 14, 2009.

  1. hi all,got a 1980 gsx250 only the right side has spark its not the coil and its not the pick ups can any body suggest wat else it could be,cheers...phil.

  2. The plug lead?
  3. nah mate leads plugs coils and the pick ups(signal generator) all o.k..thanks all the same
  4. If that's the case, you have spark then.

    Look further.
  6. So if I understand correctly everything up to the sparkplug works fine - but the plug itself won't spark?
    You have tried replacing the plug I take it?
  7. The plug, plugcap, lead, etc must be buggered, or it will spark.

    Pretty hard to tell over the net.

    Can you use a digital multimeter?
  8. Ok..the plugs are fine,the coils are fine I've tested them,the pick ups are fine they came off a running bike,but the left side wont spark,theres power to the coils I tested that with a test light,on the right side the test light would come on and then go completely off when i cranked it over but the left side wouldnt go completely out it was only dimmer not off like the right side..yes i have and can use a digital multimeter..thanks
  9. Does it have points or electronic ignition?
  10. Do you know for a fact that it is sparking in the cylinder? Because it could be that your pistol rings are buggered, and you're not able to get combustion properly, resulting in no "bang" in the cylinder... so check the compression on that cylinder against a) the compression on the other cylinder and b) against the bikes specs.
  11. What are the resistance across the primary and the secondary on the coils?
    What's the resistance in the plug caps?
    Have you replaced the plugs recently? If so are they the same as the ones that come out? The plug catalogues are not always right.
    How do you know its not firing? Have you checked the plug out of the head?
  12. Just on the offchance, swap the plugs over. Over the years i've had more than a couple of NGKs that were dead out of the box. Caused me no end of frustration by assuming that a new plug would be OK.
  13. yep too all of the above..all those things have been checked and double checked hell ive lost count on how many times ive checked those parts,keep coming with the ideas guys,thanks.
  14. Check the Earth to the coil, on the dead side. This includes the coil mounting bolts. Do it thouroughly. Give me a full report. We will get this , I reckon.

    What suburb are you in?
  15. yeah the coils are all good i switched the power leads to the coils over and get the dead side (left side)sparking when i do this.the power is getting to the coil on the left side but isnt clean like the right side.when i put a test light on the coil power leads the light comes on then goes completely off when i crank the engine over on the right side(good side) but the left side doesnt quite go all the way off it just went dimmer not all the way out like the right side did..im in thornbury.cheers.
  16. Hang on.

    I've just reread your post about the test light at the coils.

    If I read it correctly, this is testing for volts at the coils. If the light never goes out completely, then the circuit is never completely interrupted, which is a vital requirement if the coil is to produce a spark.

    So, from this, I'd surmise that whatever is wrong is upstream of the coils.

    If you had points ignition, my first thought would be to check that the LH points were actually opening and not bridged by any metallic fluff.

    As the GSX IIRC had a black box and as you mention pickups, that's probably not the case.

    Assuming that the black box operates as a set of electronic points with no other differences (reasonable on such an early unit), I'd guess that the power feed TO the coils is hot at all times and the "points" operate by earthing and de-earthing the other side of the coil.

    If this is the case, the symptoms you describe could be caused by a short to earth somewhere in the connection between the coil and the black box.

    So, I'd be looking very carefully for uninsulated spade connectors touching frame members, chafed insulation and/or build-ups of conductive shit that could provide a (not necessarily obvious) conductive path. It's probably not much, given that your test light dims, but it would certainly be enough to upset the wonders of electromagnetic induction.
  17. yeah cool I'll have a good look and let ya know how i went...could a cdi unit cause this problem? cheers.
  18. Well I wouldn't say it couldn't.

    However, in my own experience, the black boxes on early 80s Jap bikes either work or they don't, with no half measures so I wouldn't regard it as likely.

    The only real way to tell would be to sub in a known good unit to see if it helps.

    I reckon a check for leakage to earth would be more fruitful if you haven't got a spare box to hand.
  19. Pat, you and I are coming at it from the same direction. I wanna see this bike. This one will be easy, if it is in front of me.
  20. hey all..ok i swapped the wires coming out of the cdi unit that go to the coils and got spark on the other side (bad side)and none on the good side, so this tells me the cdi unit is knackered,yes?