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Thread: RB 30 flat spots

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    RB 30 flat spots

    Hi Everyone.
    My patrol has multiple flat spots between 1000 to 2000 revs when under load. The vehicle runs well over 2000 revs and has done many good miles on the open road. This has been an issue for an extended time and been serviced by many people to no avail. The engine is RB 30 with a gas conversion, manual transmission. Apart from the gas conversion, no other modifications.

    Initially I thought it was carby issues and did a complete dismantle, clean and service kit with no improvement. Realised then that the issue occurred on gas as well implying that it isn't a blockage in the carby. It is worse on gas and improves with higher octane fuel.

    Checked all vacuum lines are correct. Found a faulty vacuum advance unit and replaced it. Also found centrifugal advance was sticky so cleaned and freed up that. Still no luck. All high tension leads are good and plugs have been replaced several times in the process.

    I hope the brains trust out there can offer some suggestions because it has got me beat.
    Regards,
    Lionel

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  3. #2
    Patrol God mudnut's Avatar
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    Welcome back to the forum. Since the problem is occurring on both fuels I think it points to an electrical problem, or the second stage of the carby sticking or slow to open. Did you check that the choke break diaphragm ( on the top rear passenger side of the carby ) is not split or holed?
    My advice is: not to follow my advice.

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    Thanks for the response. I checked the operation of the choke break diaphragm when i did the service of the carby and since then has not presented any problems. Will double check it though. Will take the carby off and thoroughly check the operation of the second stage. I recall another thread discussing a sticky second stage so will look back at that also. Re the electrical side of things I'm at a loss. There are no problems at cruising and higher revs where I would expect issues wih coils or transistor assisted ignition to show up. I even disconnected the rev counter unit to see if that had any effect but same problem.
    Lionel

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    Hi Mudnut.
    I have removed the carby, stripped it and cleaned thoroughly. Checked all diaphragms and the operation of the second stage. All seems to be OK. When separating the throttle body from the main body I found one of the three bolts was slightly loose. It was the one with the bleed up through its centre. Also the screws that hold the two small venturi in place were not as tight as I would have expected. Have tightened everything accordingly. Will put the carby back on tomorrow and see how it goes.
    L

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    Patrol God mudnut's Avatar
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    The extra weight of the gas set up can cause those bolts/screws to loosen. Let's hope you have solved the problem.
    My advice is: not to follow my advice.

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