How to set the Mikuni carburettor float levels

Updated February 21, 2017

Mikuni carburettors, commonly installed on motorcycles ranging from small single cylinder dirt bikes to v-twin motorcycles, have a plastic float to regulate fuel consumption. The float in the Mikuni carburettor sets the height of petrol that rests inside the bowl. If you set the float too high, you risk petrol overflowing from the carburettor and if you have it set too low, you risk running out of fuel when you have your motorcycle at higher throttle positions. Mikuni has specific measurements for setting the float levels.

Remove the four screws that hold the float bowl onto the bottom of the carburettor. Pull the float bowl and float bowl gasket off the carburettor. Use a Phillips screwdriver to remove the float bowl screws.

Place the carburettor upside down and let the float rest against the float needle. Do not touch the float at this time.

Measure the distance between the gasket surface located on the bottom of the carburettor to the edge of the float. On a 24 mm (1 inch) Mikuni card, the distance between the gasket surface and the float should be 24 mm (1 inch). On a 20 mm Mikuni carburettor it should be 20 mm (7/8 inch). Use a precision ruler for this.

Bend the metal tab on the float that rests against the float needle. Bend it towards the float needle if the measurement is shallow and away from the needle if the measurement is too much. Use you finger to bend the tab. If you cant bend it with our fingers, use a pair of needle-nose pliers. Make very small adjustments to the metal tab and then recheck the measurement.

Things You'll Need

  • Phillips screwdriver
  • Precision ruler
  • Needle-nose pliers
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