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  1. #1
    CB750 New Member 4given's Avatar
    Join Date
    Jul 2018
    Platteville Colorado

    #3 fires when it wants

    Yes I have read on this forum
    Yes I have googled other forums as well
    Yes I have found similar topics

    I have a 75 cb750 motor(told it belonged to John Soliday)
    Dyna electric ignition, Accel coils/wires, Nkg plugs, 7A carbs,

    So what's going on is
    #3 doesn't always fire and never at idle
    I've gone through my carbs even put on a freshly rebuilt loaner set, I am getting fuel
    With no change
    Have swapped plugs and wires,
    Even re wired coils so as to fire 1/4 off 2/3 and vise versa, I am getting spark
    No change
    Compression is 155-165 across all 4

    At idle #3 only warms up if i go ride it it well sometimes fire in 2nd gear rpms aournd 6k rpm
    And ALMOST always in 3rd & 4th gear 5-6k rpm

    I'd say carbs but even after cleaning mine it didn't help so I put on a set my friend just rebuilt with no luck either
    I adjusted valve .002/.003 had some noise so buddy that I got it from said it's got a preformance cam and to set it .003/.004
    I did no change

    Driving me nuts

    If any buddy thanks the can help I'll even give you my cell# so we can talk

    Thanks fellas

  2. #2
    Moderator dirtdigger's Avatar
    Join Date
    Feb 2012
    Black Hawk SD
    Is the plug wet? If its wet the no spark or mechanical issue. If its dry no fuel and still could have a mechanical issue if you have a wiped out lobe...intake not opening letting in fuel air mixture...or exhaust not opening causing similar issue. If it was a new cam put in with old rocker arms it can easily and very likely destroyed a cam lobe.

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