Motorcycle Questions? Ask a Mechanic.
Hi and thank you for your question.
There are a couple of solutions to the problem. First, the problem is the plunger for the enrichener mechanism is stuck in the carb body. If the ultimate goal is to get the carbs cleaned, you can kill two birds with one stone. Get yourself a bottle of Yamaha Carb Cleaner/dip. Available from a Yamaha dealer. It is a quart bottle and typically runs between $12~$15.
Mix it with 2 quarts of water. Find a metal container just large enough to fit the carb in. Now, place the carb in the container, pour the solution in the container and place it on a hot plate. Watch the hot plate and slowly turn the temp up so the solution is hot but NOT boiling. Ideally somewhere around 150 degrees. Soak it for about an hour. Two things are going to happen, the cleaner will work to break the corrosion and the heat will expand the aluminum more than the brass. Remove the carb and pull on the cable to free the plunger. Rinse the carb off with clear water and blow out all internal passages with compressed air.
The other alternative would be to use PB Blaster penetrating oil and keep spraying it on top of the plunger. Give it several days to soak all the way through then start checking the plunger daily to see when it frees up. Don't pull on the cable too hard because you can spread the end of the plunger that retains the cable and if it spreads, the cable is going to come out then you have bigger problems.
You are most welcome.
Just be judicious in your use of force. Start out gently and progress to a mild tug, pulling on the cable with 2 fingers.. I would suggest the heat and carb clean first because it is attacking the problem on the 2 fronts. The corrosion and expanding the aluminum to help it break loose. If you would rather give it a shot without taking the choke cable off the bike, use the PB Blaster. Just be patient with that. It could take up to a weak to fully penetrate.