Pistons & Suction Chambers
The piston and suction chamber form the variable-choke mechanism at the heart of the SU carburettor. The piston rises and falls with engine demand, varying the throat area and maintaining constant depression over the jet. Any wear, corrosion or damage causes mixture problems no adjustment can fix.
Common symptoms of a worn piston or chamber: erratic idle, poor cold starting, mixture hunting, or a piston that sticks, rattles or rocks.
