Testing your choke
When the choke is closed, engine cold, the fast idle cam will be positioned so that the idle screw is sitting on the high step. Adjust the fast idle using the Idle screw.
If the piston is frozen remove the aluminum plug at the bottom of the piston well and tap the piston out with a brass drift punch. Clean so that the piston will move freely. These pistons are not available so be careful not to break the lever, or stem.
The hot air connection is used to connect the hot air tube. Vacuum supplied to the choke housing pulls the hot air into the choke housing. This heats up the choke thermostat, which then will open up the choke valve.
The choke rod connects the fast idle cam to the choke shaft and is used to move the fast idle cam.
Watch a video about the YFA Choke: