The float needle bears against the seat at the bottom of the brass seating bush. If the seat is damaged the float chamber will have to be replaced. Early models of the Concentric were fitted with plastic float needles which should be replaced as a matter of course with the current Viton tipped float needles. Viton tipped needle valves are much more resistant to wear but should be replaced if there are visible signs of wear, contamination, or damage.
If a punctured float is suspected, submerge the float completely in fuel for 15 minutes and shake it to see if any fuel has leaked into it. Check the float tabs for signs of distortion, and check that the float spindle is an easy rotating fit in the float with no stiffness or excessive play.
The All New AMAL Concentric StayUp Float
The AMAL Carburetter Company, (Burlen Fuel Systems Ltd) manufacturers of all genuine new AMAL Carburetters and spares Worldwide, have introduced a revolutionary new float for Mk1, Mk1.5 and Mk2 Concentric AMAL carburetters.
The new adjustable height StayUp float is resistant to modern ethanol based fuels and has a military spec closed cell construction making it puncture proof. The ability to adjust the float arm allows for quick and easy minor alterations to float levels where required.
The material specified was used by the S.U Carburetter Company for military installations in the 1980s, where a guaranteed fail safe operation was critical. Due to the close link between S.U and AMAL today (both owned by Burlen Fuel Systems Ltd), the secret behind the material has been released and upgraded for the manufacture of this float, making it virtually unsinkable.