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Thread: High rpm cutout

  1. #1
    CB750 New Member Silentyoda's Avatar
    Join Date
    Feb 2021
    Portland, Maine

    High rpm cutout

    So i have a 1981 DOHC CB750C, runs great at an idle; but as rpms climb while riding it cuts out as if it's not getting fuel/air. I suspect electrical to be the cause. Reasons being that I have completely disassembled all 4 carbs and rebuilt them. Charging system is all new and verified that it's charging. New regulator rectifier, rotor, and stator. Motor in the bike now I believe has 36k miles (I have a second original motor with 153k on it) To say the least, they bike has been rode an absolute ton. I suspect maybe the coils are the cause but I'm unsure of how to test for that. If you need more information please ask, would like to be able to get the bike up and running for this summer again.

  2. #2
    CB750 Guru amc49's Avatar
    Join Date
    Sep 2015
    Fort Worth TX.
    Set your valves first, nobody ever does it and the single biggest cause of them not revving fully out without missing. Number two reason will be pods if somebody has put them on and then after that ignition, they are weak there.

    Rebuilding carbs? Many do it 2-3 times to still have trouble with them.

    Set the valves to .005" instead of service manual .003", it allows like 3X time before having to do them again.

    Coils can be checked for absolute working but not for strength, replacing is all you can do to be sure there.

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