Specifications

free by prying gently under the head with a screwdriver until it can be gripped with pliers

and pulled out. The BS34 float needle is retained by a screwed-down tab, and it is

Viton-tipped; avoid contact with solvents. The BS34 seat is push-in type, sealed and

secured by an O-ring. There is a fuel screen above the needle seat in many BS34

carbs. Be sure it's clear. Clean with solvent and compressed air. Again, keep seats and

needles paired.

If the carbs have been in recent service, shake the floats. If you feel fuel sloshing in

them, replacement is the best course, although brass floats can be soldered. If the

carbs have been out of service, put the floats in a container of gas with a lid tight

enough to push them below the level of the fuel and let them sit overnight, then inspect.

Adjustment

Float level is adjusted by moving the tang that contacts the float needle. Floats must be

level (same reading on each side); this is done by adjusting the bridge between them.

Carbs must be adjusted to the same float level.

If the float bowls are fitted with drain plugs, fuel level can be inspected directly by fitting

a piece of clear hose to a plug and inserting the plug in the float bowl. Some float bowls

are fitted with drain valves opened by a screw, with a hose nipple on the outlet. To read

fuel level, attach the sight tube to the outlet and set vacuum petcocks, if fitted, on

"Prime," and open the screw until fuel flows into the sight tube. With the motorcycle

level, hold the sight tube upright beside the carburetor body. Fuel should rise in the tube

no higher than the lower lip of the carb body where it overlaps the float bowl, and no

lower than 2 mm. below it.

A second procedure is to read float height. This is measured from the surface on the

carb body on which the gasket seats to the top of the float, with the gasket removed. If

the gasket cannot be removed without damage, reduce the specification given by 1 mm.

and measure from the gasket. Holding the carburetor with the floats up, lower the floats

gently onto the float needle, taking care not to compress the float needle spring. Since

the reading is taken with the carb upside down, raising the float level will lower fuel

level, and conversely.

All BS38 carbs are set at 24 mm. +/- 1 mm.

For early BS34 carbs with brass floats, a float height of 27.3 mm. +/-1 mm. is specified.

For later units with plastic floats, 22 mm. +/-1mm. is given. The usual recommendation

is to use the specification given for the float type. All BS34 carburetors have a drain

valve at the bottom of the float bowl (see above). Fuel should rise no higher than the

lowest point of the flange on the carburetor body, and no lower than 2 mm. below that

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