I have to agree with firehog.
You need to get access to the carb and remove the spark arrestor (looks like a chromed air filter on top of the carb) when the engine is cold and look down the inlet to the carb. You should have 2 butterfly valves in the carb, the lower one is the normal throttle valve, the top one is the choke.
When the engine is cold, the top butterfly should be closed (blocking the inlet to the carb, it won't completely close, but should be close to fully closed). If the butterfly is closed then the problem is unlikely to be the choke. If the butterfly is open, then either you have a defective choke or you are using the wrong procedure to start the engine.
You state that you have a carb, so when the engine is cold, before you start the engine, you should fully open the throttle twice by pushing the throttle control fully forward, then back to it's neutral position and fully forward again and back to it's neutral position. This does two things, the first is it will allow the choke butterfly to close (assuming your choke is automatic) and the second thing is that the accelerator pump will have squirted 2 doses of fuel into the inlet manifold which help a cold engine start.
You should then turn the ignition key and start the motor. Some carbed engines have the idle set faily low when hot, which often means the idle is too low for the engine to start when cold. This means that you may have to give a small amount of throttle when starting the engine from cold. Most throttle controls allow you to pull the throttle lever out and then move the throttle without engaing forward or reverse.
Hopefully some of this helps. Don't forget to put the spark arrestor back on at the end!! You only removed it to check the butterfly valve, not to use it like that.
Gary
