Standard 1300 x flow with standard single choke Ford carb (may be off a Fiesta, No 771FK1A 81A) K & N filter fitted. Revs well if throttled fairly gently but chokes if booted. However if it is revved using the connector rod that connects the accelerator pump (ie; under the float chamber) to the butterfly cross bar it appears to rev well. Any theories?

timing?

Blocked jet(s) .Airline through the jets.