One cylinder dead at low revs

Discussion in 'Mechanics Garage' started by Maakmy, May 3, 2015.

  1. Maakmy

    Maakmy New Member

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    Hello,

    I have a 1993 VFR750 RC36. The left front cylinder is dead at low revs?
    Please can I get some advice or solutions.

    Thank you in advance for any guidance.

    Regards
    Dean
     
  2. adeyren

    adeyren New Member

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    Touch the header (gently) is it warm/ hot? I had the same problem - turned out to be a dead coil.
     
  3. tinkerinWstuff

    tinkerinWstuff Administrator Staff Member

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    check for spark is easiest start.

    Then compression test 2nd.

    Both of those being good leaves clogged idle jet in carb.

    something in ignition system or carb is most likely culprit.
     
  4. squirrelman

    squirrelman Member

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    Clogged idle jet in that cylinder. It runs on main jet circuit but not on idle jet, therefore no spark or compression problems.
     
    Last edited: Oct 2, 2015
  5. NormK

    NormK New Member

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    The whole problem with all these things is we get very little info as to history of the bike, is it a recent purchase, have you had it for some time and this problem has just happened, has the bike been parked up for some time, was it running ok when you got it?
     
  6. Maakmy

    Maakmy New Member

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    Hello All,

    Firstly thank you all for advice and direction, I appreciate this.

    I purchased the bike second hand.
    The bike was running 100%, it was mechanically and electrically sound.
    I am trying to restore the bike to showroom condition and this is basically the last issue before it is finished.

    Yes, the bike has been standing for about a year.
    The cylinder runs over 3500 revs and is dead below this mark.

    Regards
    Dean
     
  7. tinkerinWstuff

    tinkerinWstuff Administrator Staff Member

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    Doesn't change what I said for troubleshooting the problem.

     
  8. NormK

    NormK New Member

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    Possible pulse coil gap, I had a miss problem on my CB750 that drove me nuts for months, changed swapped everything I could think of, cut connectors out, then a bloke told me to close the gap up to 10 thou and bingo
     
  9. cruzebabuze

    cruzebabuze New Member

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    check your carb linkage for synchro

    Hi there, I had the same problem, and it took me a while to figure it out, but it was the linkage for the carb synch that was wrong, as soon as I adjusted it it ran fine. be aware that you can mess it up hard and fast. so make sure you know what gen your bike is so you can start the adjustment on the proper cylinder as they are inter connected
     
  10. Allyance

    Allyance Insider

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    Don't know if '93s are like the '83s, but I have one coil for 1 & 3 and one coil for 2 & 4, therefore more than likely a carb issue.
     
  11. squirrelman

    squirrelman Member

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    In that case someone goofed up the adjustment initially. Bench synching carbs by eye should get close enough for that problem not to happen. The settings interact a little, so changing one screw to satisfy one cylinder may throw off other cylinder settings. Touching synch screws--while installed on the bike--should only be done while gauges are installed and engine running so you can see what's happening.
     
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