How to Remove and replace the throttle assembly. It is not necessary to disassemble the throttle assembly to remove and replace this on the the drive tube. It can just slide on and off the drive tube.
Step 1) Undo air cleaner cover
Step 2) Hold in throttle trigger, block carb cam with fingers, and release throttle trigger. Cable end should pop out of carb cam seat.
Step 3) Remove cable from seat.
Step 4) Undo Wire leads
Step 5) Undo the clamp bolts holding drive tube (at small end of cone shaped clutch housing). Configurations vary here, but the bolt in the position at the center of the tube goes through the drive tube. The others are just clamping bolts and do not have to be fully removed. Make sure to keep hex key firmly seated in bolt head. No gasket exists here. Pull the drive tube out of the clutch housing.
Step 6) Loosen the 2 clamp screws on the throttle assembly (front top and bottom back) ONLY. You will feel the assembly start to slide on the drive tube. Do NOT undo any other screws on the assembly. Slide throttle assembly off the drive tube.
Replace with reverse procedure. When inserting the drive tube into the clamp in the clutch housing, you will have to use good lighting to look into the screw hole for the center bolt to make sure that the hole in the drive tube lines up with the hole before you put in the bolt. You may have to wiggle the drive tube to get the drive shaft spline to mate and allow the tube to slide all the way in. Adjust position of throttle assembly so that the cable end seats properly into the seat near the carb. If the assembly is pulled too far forward, the cable may be pulled out of the seat and cause higher revs at idle.