by Adam_Winstone » Mon Aug 18, 2014 2:00 pm
If there are no mechanical issues with the motor and no air leaks anywhere (incl. exhaust nuts where it meets the cylinder) then the normal cause of not ticking over and needing choke to start is a blocked pilot jet, hence it needing to find more fuel from somewhere to run (choke system). To rule this out, remove the choke jet and poke a small piece of fine bristle or single strand of fine wire through the jet to ensure it is clear ( people warn against doing this but that is to avoid damage by being too heavy handed, so be gentle if you use wire).
You also need to ensure that your choke cable is not adjusted too tight and staying on, the carb top is tight and that the Rickover adjustment (mixture screw and air/slide screw) is set correctly.
If cleaning the pilot jet through and general adjustment doesn't cure this then we would need to think a little deeper into the motor.
Adam