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Thread: Sorted running issues 900ss

  1. #1
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    Default Sorted running issues 900ss

    Ok, so a little update, I had posted about help with carbs but after much head scratching it appeared that it was an ignition problem.

    Basically it ran but very badly, sounded like it was only running on one cylinder but when I twisted the throttle it struggled, would not rev and died. Basically it wasn't advancing the ignition with the attempted increase in revs.

    So I got a suggestion it was the ignition and this was narrowed down to most likely being the pick up coils. If they weren't working it would give the problems above. So I changed them. No difference. Then I got another suggestion for switching the polarity of the pick up coils. I thought that they could be connected either way round, apparently not cause after swapping them round now its running sweet and revs beautifully! I had copied the original wiring when putting bike back together and the coils are not the original, they had been changed prior to me getting it. but it was a non runner when I got it too.

    Lots of smoke coming out now so I am going to change oil and sparks and evaporate petrol in the chambers and try again. Then hopefully MOT!

    Thought I would post this in case anyone has similar issues.

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  3. #2
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    mmmmmm that;s making me wonder now ...... can only check at the weekend

  4. #3
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    Good to hear it is now running well Ian. The ignition module triggers off the positive-going rise of the leading edge of the pulse from the pickup. When the wires are reversed the phase is changed so the ignition is now triggered by the positive going end of the pulse, so the timing has been retarded by the pulse width. I'm not sure how much that is in degrees but no wonder it ran terribly.

    Old enough to know better, young enough not to care

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  6. #4
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    Quote Originally Posted by slickmouse View Post
    mmmmmm that;s making me wonder now ...... can only check at the weekend
    Don't bother. Your bike uses an entirely different ignition system.

    Old enough to know better, young enough not to care

  7. #5
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    Quote Originally Posted by Derek View Post
    Good to hear it is now running well Ian. The ignition module triggers off the positive-going rise of the leading edge of the pulse from the pickup. When the wires are reversed the phase is changed so the ignition is now triggered by the positive going end of the pulse, so the timing has been retarded by the pulse width. I'm not sure how much that is in degrees but no wonder it ran terribly.
    Makes sense now! Cheers Derek, MOT booked for next week!

  8. #6
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    Actually I'm not 100% certain whether it triggers off the positive edge or the negative edge of the pulse. If it's the negative edge then the ignition would be advanced but the result is the same, it will run crap.

    Old enough to know better, young enough not to care

  9. #7
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    It is suprising how many problems that appear to be fuel turn out to be electrics...

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