The engine control linkages connect the driver's accelerator and choke inputs to the carburettors. The 1275cc and 1500cc systems differ substantially in their mechanical layout, and there were also changes within the 1275cc range.
1275cc Throttle & Choke
Early 1275cc Midgets to approximately 1970 used a floor-hinged accelerator pedal with a cable running to the carburettor throttle link and lever assembly, the throttle return spring ensuring the carburettors close when the pedal is released, and from around 1970 a revised pedal and cable arrangement was introduced, although the basic principle of cable operation remained the same. The choke cable runs from a dashboard-mounted knob through the bulkhead to a pin connection at the carburettors, two choke knob styles being used, a small round knob on earlier cars and a star-pattern knob on later models, with a grommet sealing the cable where it passes through the bulkhead and a cleat securing it to the heater case, and two carburettor return springs, one per carburettor, ensuring the choke mechanism returns to the off position.
1500cc Throttle & Choke
The 1500 uses an entirely different accelerator pedal and cable arrangement to suit the Triumph engine's throttle linkage, the twin SU HS4 carburettors using a bell crank and link rod arrangement rather than the direct cable-to-lever system of the 1275cc. The throttle cable connects to a bracket on the inlet manifold, and the bell crank translates the cable pull into the correct movement for the carburettor throttle spindles. The choke cable on the 1500 is a different length from the 1275cc item and connects to the carburettors via a pin fitting, and as with the 1275cc a grommet and cleat are used at the bulkhead, but the routing differs to accommodate the revised engine bay layout.