SU Carb FLOATBOWL LIDS .

The SU carb by design has to have the floatbowl vented to allow displaced air to be expelled from the top as the float moves upward .

The design is easier to understand if you lift your toilet cistern lid { Floatbowl lid }.

You will notice there is a float sitting on top of the water { Fuel }

Now if you flush the toilet you will see the water { Fuel } falling down the cistern { Floatbowl } as it flushes the toilet { Fuel flowing to carb body }

As it refills the float rises and shuts off the water { Fuel } flow ;

If it does not shut off , then the cistern { Floatbowl } will flood .

Look near the top of the cistern and you will see a pipe hole near the top .

The pipe hole is the overflow and if your float system does not shut off the flow of water then the excess will flow out the cistern { Floatbowl } and out of the cistern { Floatbowl } via the pipe to the drain . This means that your toilet floor { Engine } does not get a soaking with water { Fuel }

The early SU carb does not have that overflow to take the fuel away , it only has a hole where any petrol overflow is chucked out onto the engine ; EEK ; EEEK ; EEK

The early SU carbs fitted to the Reliants had only a single fuel feed pipe into the lid and a hole in the lid with a little cover over it to prevent blockage ; as per

I would advise any SU carb owner to upgrade to the later 2 pipe floatbowl lid as per ;

The vent / overflow pipe can have a length of fuel hose attached and taken to a safe position away from the electrics / exhaust to the rear of the driver / rider .

I would also advise fitting the

SU Carb FLOATBOWL KIT ; Floatbowl Kit ; Anti-Flood Kit for HS2 , HS4 & HS6

The above floatbowl kit contains an adjustable float and , on the Burlen SU carb site ,

it does not have any specific measurements relating to the minimum and maximum

height settings for that new float .

R3W forum member Dranreb contacted Burlen on 4 August 2011

and was informed that the settings for the new float were the same

as the older HS carbs with the early nylon float and steel needle .

The gap between the lever and the face of the lid should be between

0.125” { 3.17 millimetres } and 0.187” { 4.75 millimetres }

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