how to set the choke...
with a COLD engine , press the acc and release it , this sets the choke on with a cold engine. dont switch on the ignition at all. take the air filter off and look at the choke cam and choke butterfly , they should look about like this...
note there should be a small ish (about 5mm sounds right) gap in the butterfly.
with a HOT engine (one thats been running for about 15 mins or so) , switch off , remove the air filter and go and look again. it should look like this...
you can adjust it by loosing the three screws on the side of it and turning it slightly. hold the throttle lever clear of the cam when you are adjusting it.
only slacken the screws about a turn or so. they do get lazy when they are old though and dont always fully open. its just a heated coil element.
dont have any more pics to hand. hope that helps a bit.
also test that when the ignition is on the wire at the choke element is live.
it might be best to just replace the choke element if in doubt , they are relatively cheap.
im sure moby
could explain it better.