Tuesday, April 29, 2014

How to Sync Flat Slide Carbs

How to Sync Flat Slide Carbs

An erratically operating motorcycle engine signals problems with the combustion system. A sure-fire cause tends to be either poor performance or a misalignment of the carburetors when running a dual system. Flat slide and round slide carburetors cause the same bad engine operation; flat slide carburetors are just more sensitive and responsive. Syncing the carburetors correctly can solve some engine problems, smoothing out the fuel and air delivery to the engine.

Instructions

    1

    Use a screwdriver and crescent wrench to remove the motorcycle bodywork so you can access the flat slide carburetors easily. Pull or temporarily remove any hoses or electrical wiring in the way of your access as well.

    2

    Locate the idle-mixture fuel needle on both flat slide carburetors. Use a screwdriver to turn both needle screws in all the way -- turning to the right. Back the screws out with the screwdriver the correct number of turns on both carburetors consistent with the carburetor tuning providing in your motorcycle repair manual -- the number of turns varies by model. Confirm both flat slide carburetor needle screws are turned back out the same number of turns.

    3

    Check that the fuel supply is on and the fuel hoses are connected to both carburetors and turn on the motorcycle. Wait 5 minutes to allow the engine to get warm. Do not start pulling away on the throttle. Just let the engine idle. Attach the carburetor balancer tool to the carburetors.

    4

    Locate the throttle shaft shared by both carburetors. Twist the throttle shaft controls with a screwdriver so that the setting matches the readings displayed on the carburetor balancer tool. Pull the throttle a few times slightly while monitoring the readings on the balancer. Continue to adjust the shared throttle control while checking the balancer tool readings until each of the adjustments on the throttle control are matched.

    5

    Test the engine with some minor sustained throttle pulls on the throttle handle. Continue making adjustments until the engine cycles smooth out as it is running -- no burping, stalling or uncontrolled revving.


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