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One Cylinder Spark Tests - Interpretation?

Discussion in 'Supersport (1974-2007)' started by chueewowee, Nov 23, 2017.

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  1. Dear Folk,
    Could you help me in my interpretation of a recurring symptom and my electrical tests, please? I wonder, Should I immediately replace horizontal pickup coil and see result, or perform other tests; The alternator wires being hot is on my mind - I wonder could the alternator interfere with a pickup coil?

    Thanks in advance for your reading this and being concerned. Symptoms are followed by Ignition test results below:

    Symptoms
    ==============
    A recurring problem: Horizontal cylinder cuts out when hot at decent RPM with hard riding resulting in failed spark; when running, plug quickly soots up even at idle = weak spark.
    - swapped coils, leads, CDI and problem did not follow.
    - Alternator twin wires feel rather hot.
    - A common 10% voltage drop in the ignition feed (to both coils) I suspect, is due to kill switch, which is cracked.

    IGNITION CHECKS: [H/V = Horizontal/Vertical cylinders]
    - tests performed with digital multimeter
    =====================================================

    CONTINUITY/OHMS IGNITION COILS
    - primary circuit (H/V) 4.3/4.5 ohms = PASS
    - secondary circuit H/V = 15.33/15.54 Kohms = PASS (10 -16 kohms)

    VOLTAGE SUPPLY to the IGNITION COILS
    - At battery (12.46 V): = 12.71 V
    - leakage test = 0 milliamps = good.
    - at ignition feed loom branch plug: red = 11.07 blue = 0.146 Volts DC
    - Ignition coils (H/V) : 11.34/11.26 V
    - CDI feed (H/V) 11.23 /11.32 V = 10% drop

    AC VOLTAGE at PICKUP COIL - starter motor engaged
    - (H/V) 0.09/0.12 V

    - PULSE VOLTAGE from CDI - starter engaged/motor running
    - (H/V) 10.85/10.04

    VOLTAGE FROM CDI - ignition on
    - (H/V) 0.01/ 0.023 volts

    PICKUP SHORT CHECK (ohms) - CDI disconnected
    - (H/V): infinity/infinity = PASS

    DC VOLTAGE SUPPLY - TCI TO SENSOR - ignition on
    - not available..yet

    DC VOLTAGE SUPPLY, TCI TO COIL - ignition on
    (H/V) 0.01/0.03 Volts

    DC VOLTAGE PICKUP COIL to Ground (leakage)
    - not available... yet

    CONTINUITY/OHMS CHECK PICKUP COILS
    - (H/V) 96.5/96 ohms = PASS (95 - 105)
    - NOTE: insulation pickup coil wiring is tatty at CDI end... should I rebuild this loom with shielding?

    CONTINUITY/OHMS CDI
    (H/V).= 2.009/2.372 kohms = PASS
     
    #1 chueewowee, Nov 23, 2017
    Last edited: Nov 23, 2017
  2. If the problems not moved then I would suggest it was the pickup coil. They can appear fine and break down when hot. I have looked into this previously on my own bike. The impedance test alone cannot tell you if the pickup coil is good. As they are so old I would just replace them as I did with two from Electrex World. If you are going into the side case it makes sense to do them both.
     
    #2 Desmoquattro, Nov 23, 2017
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  3. I guess the power to the pickup coil isnt provided by the alternator, but by the CDI itself?
     
    #3 chueewowee, Nov 23, 2017
  4. The pickup coil plugs straight into the cdi so yes
     
    #4 Desmoquattro, Nov 23, 2017
  5. Ok thanks pal. Ill do what you suggest, as do symptoms and test results, and also test alternator as a seperate issue whilst at it.

    I dream of fat sparks.
     
    #5 chueewowee, Nov 23, 2017
  6. Check the wiring on your alternator that there's no corrosion anywhere making a bad connection increasing resistance therefore hearing up. Check voltage at battery while running at about 3000 revs. Voltage should be around 14 volts approx. This will drop when at idle. This indicate alternator is charging. If it's just the one cylinder it's gonna be something specific to that cylinder. From what you describe my money is on the pickup coil. Leads and plugs Ok?
     
    #6 Desmoquattro, Nov 23, 2017
  7. I would eliminate that the problem with your horizontal cylinder failure isn't due to low cylinder pressure because of valves not sealing well.
    A quick compression check to compare horizontal and vertical cylinder pressures might reveal something.
     
    #7 CRYSTALJOHN, Nov 24, 2017
    Last edited by a moderator: Nov 24, 2017
  8. Agreed... and was the first thing I did - readings with 'push bung fit' guage:
    compression H/V = 136/130
     
    #8 chueewowee, Nov 24, 2017
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  9. When I got my SS, I was warned by a local expert that alternator nuts come loose, so listen for rattles/knocks.

    Sure enough, it happened and I lost one cylinder at the same time. This was due to the wobbling flywheel taking out one of the pick-ups, Cure was to tighten the nut and and replace both pick-ups.

    As your fault doesn't follow swaps, it is almost certainly a pick-up imho. Electrex do pick-up kits pretty cheaply but you need to be handy with a soldering iron as they are (or were) not quite plug and play, so you need to join to the existing wires.

    If you dream of a fat spark, get some CCW ExactFit coils from @Exige . The CCW coils I fitted to mine completely eliminated plug fouling and gave improved throttle response as well :)
     
    #9 Old rider, Nov 24, 2017
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    • Agree Agree x 1
  10. cheers for that old rider.
    Two exige inits on order.
    I take it you solder the wires, but outside the casing?

    Problem with my alternator retaining nut is that I cant budge it! Ill be needing an air wrench.
    I seem to remember i tried a long bar on it, but trouble was a danger of twisting on the nut.

    I do like the idea of those coils - something for after christmas, i think.
     
    #10 chueewowee, Nov 24, 2017
  11. Yes the soldering is outside the casing but if they are from Exige rather than Electrex, maybe they come full length with plugs?
    It’s a while ago now but I’ve an idea the pick ups might work on the outside of the flywheel. If they do, you won’t need to touch the nut.
    If you do need to remove it and it won’t budge, you could cut it and then replace it with a pair of Nicol Engineering locknuts.
     
    #11 Old rider, Nov 24, 2017
  12. hmm, having no idea on the set up how would that affect the timing and triggering if the flywheel will be effectively turning in reverse according to the pick up's? just interested.
     
    #12 finm, Nov 24, 2017
  13. No need to remove the alternator nut the pickups are on a rail on the outside edge of the flywheel and held in place by two screws. Easily removed.

    When I removed the flywheel nut I used a large breaker bar, big socket and jammed a copper 2 pence in the gears behind the flywheel. It locks up the engine and the coin gets chewed up in the process causing no damage to anything else. Surprisingly effective, not a steel one, test with a magnet or results may be somewhat different!
     
    #13 Desmoquattro, Nov 24, 2017
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  14. Great idea for flywheel budging - whenever i ever need to ever.

    The Electrex pickups will need joining. I like soldering - seems more permanent than dodgy crimps but an aircraft engineer told me they prefer crimps because there is no heat damage to fine wire. I see ducati use crimp only too, on terminals. And heat can melt a solder joint (but so what, it also burns sleeving and creates shorts). Dont like fat plastic coated crimp spicers - i’ll solder.

    What about using copper sheilding too - is it worth it?
     
    #14 chueewowee, Nov 24, 2017
  15. No copper shielding on my bike and it was fine
     
    #15 Old rider, Nov 25, 2017
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  16. Use heat shrink on your joints for extra protection and neatness. As regards the shielding, if you ever plan to run an Ignitech unit in the future they are sensitive to outside interference so there's no harm in it. But only if you plan this upgrade later on. Make sure the new pickup wires are away from the HT leads as they can cause issues.

    Ian
     
    #16 Desmoquattro, Nov 25, 2017
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  17. Btw, if you lean the bike well over to the right, you don’t need to drop the oil:)
     
    #17 Old rider, Nov 25, 2017
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  18. Yes this makes it a lot easier, I've heard this before but it's a tricky one leaning it over.
     
    #18 Desmoquattro, Nov 25, 2017
  19. Just stick a big Phillips screwdriver through the redundant hole through the engine and lean the handle on something solid like an axle stand or section of tree stem
     
    #19 Old rider, Nov 25, 2017
    • Like Like x 1
  20. Ah, that's a good idea!
     
    #20 Desmoquattro, Nov 25, 2017
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