Popping on left side on overun!

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    1978 B3 carbs rebuilt all exhaust joints sealed. Starts fine runs ok but there is a popping sound at tickover and when bike is on the overrun.

    If I raise the choke lever just alittle bit the popping stops!!!

    I have tried the air mixture screw adjustment but am unsure which way to turn it to weaken or richen the mixture.

    Any ideas and comments please.

    Thanks Sam


    Hi Sam

    It does sound like a fuel mixture issue. Have you checked the carb to head rubbers for perishing or leaks? If air can enter this will potentially weaken the mixture. Also are the carbs well balanced?

    When the mixture screw is fully in place it shuts off the air. I always start at one and 3/4 turns out then use a colourtune plug to adjust either way as required. If you are not familiar with a colourtune plug it replaces the plug in each pot and as it has a glass base you can see the colour of the explosion in the cylinder and adjust until the colour is correct. Once happy with the settings re balance the carbs.

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