how to diagnose bad spark plug and cdi?

Discussion in '2-Stroke Engines' started by iron_monkey, Mar 5, 2009.

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  1. iron_monkey

    iron_monkey Guest

    My magneto reads 350-400ohms, which means its supposedly fine from my forum searching.

    What isn't clear is how to diagnose a bad cdi and spark plug? (All connections checked, kill switch bypassed)

    Its plenty clear something in the electricals failed as my engine suddenly cut out while idling, compression is still normal. Has a good record as its been maintenance free and easy to start for its roughly 1000km of bumpy road use. Now its completely dead, not a sign of life while trying to start it.
    Last edited by a moderator: Mar 5, 2009

  2. Pablo

    Pablo Motored Bikes Sponsor

    So you don't get spark when you turn it over by hand? (plug out, no compression)
  3. iron_monkey

    iron_monkey Guest

    Turns out it was a fuel line that was on the verge of escaping from the inlet and wasnt bringing fuel to the carb. I inadvertently yanked it or something. The fuel valve was half open so it was only dripping fuel (hence i didnt notice). Business as usual now.

    It be good if this question was answered for the benefit of others.
  4. pilotpeat

    pilotpeat Member

    A friend of mine who lives in a different state was having problems with his scooter-it would start and run fine in the morning when it was cold but after work when it had been sitting in the sun all day it wouldn't start.

    The shop he took it to was a "Harley" shop, they were the only shop he could find that knew what they were doing. (funny side story-the guy that ran the shop didn't want anyone to see him riding a scooter so to get it warmed up he had his helper ride it around the building 30 or 40 times)

    Anyway, once they got it warmed up it wouldn't run or start. So he pulled the CDI out and put it in the freezer for 20 or 30 minutes, and when he hooked it back up, started and ran fine. So new CDI and everything works great! The CDI would only work when it was cold. Once it got hot from running or sitting in the sun, it wouldn't work again until it cooled down.

  5. fetor56

    fetor56 Guest

    Sorta on the same subject;if u have a failed PC hard-drive & put in in the freezer overnight there's a good chance in the morning it'll work for a little while.......while it does extract ALL the info u can from it.
    Amazing things those freezers.