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Float height

In carburetors, fuel is filled in the carburetor bowl and then supplied to the jets. there is a set level that is maintained to assure a sufficient supply of fuel to the jets. and that level is adjusted by afloat. when the bowl is filled up the float raise and closes the valve that supplies the fuel and then as the fuel is consumed the fuel level drops with it the flot goes down and that opens the fuel valve again to replenish it.


Float Hight is too high: if the float height is too high that will raise the fuel level in the carburetor bowl. if it is raised too high then the fuel will leak into the engine uncontrollably thus causing a rich condition.

Float level is too low: if the float level is too low then on high speeds the carburetor bowl won't replenish enough to reach the main jet. this will cause sudden power drop or hick-ups at full throttle. normally if the float height is low then the engine will run leaner .and  the spark plug color will appear white.


Rule No.1: on most carburetors, the float height is set adjacent to the carburetor body. but float height varies from motorcycle to motorcycle. so always consult the service manual for guidance.

Rule No.2: place the carburetor on the side. float side facing right. then tilt the carburetor to the left at 45 degrees angle. most carburetors are adjusted on this angle because at this angle float is hanging free and you can adjust float height better from this angle.

measuring float height angle with protector

before adjusting float tilt the carburetor to 45 degrees for proper adjustment. or look for the specific angle for your motorcycle carburetor in the service manual.

carburetor float


float valve

Float valve

float valve seat

Float valve Seat

float valve with seat

Float valve Position towards it's seat

float valve

there is a Groove on the upper side of the float valve for the float to settle

bending float tab

push the tab on the float to decrease the fuel height in carburetor bowel

lifting float tab

lift the tab on the float to increase the fuel height in carburetor bowel

float valve push pin
float valve push pin compressed

there is a dampner on the top of the float valve 

float height too low

adjust the float height where is touches the dampner pin

float height too low measuring

there is a line that is at the side of the float, for  most carburetors that line is set parellel to the 

float height low reference

consult your motorcycle service manual for the correct float height for your motorcycle

float height too low example

Float height set too low

float height too high example

Float height set too high

correct float height example

correct float height

correct float height example

correct float height

Learn more about carburetor tuning in following articles

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