Modern Vespa

My GT200 is once again stalling and once it stalls it is hard to start. I noticed that the mechanic did drill a hole in my gas cap

and did detach the evap line that goes into the carburetor.

As I inspected the gas line from the tank to the carburator, I notice that the fuel line that leaves the charcoal canister below the gas tank has an air bubble in it. I also notice that the in-line gas bulb filter is only half full of gasoline. Could this be why my scooter is stalling and if so, what do I have to do to get the air out and keep it from happening again. Any help is appreciated. Joe

The evap system is designed so that gasoline fumes from the tank don't evaporate into the air. The system incorporates a charcoal cannister to collect vapor and a rollover valve to avoid liquid gasoline running out of the tank if the scooter is laying on its side. Liquid fuel in the cannister causes poor tank venting and can result in hard starting, rough running, or stalling. Having said all this, there is a tendency for riders to blame every possible rough running or stalling problem on the evap system. It is easy enough to disconnect the hose from the carb body and see if that makes a difference. If it doesn't, the problem was not the evap system. Every gasoline car and truck sold in the US for the past several decades has a similar system.

Here's a better description of what the evap system is & does: This is from the LX150 workshop manual, to give you a better idea of how it's setup:


If the Charcoal canister is filled with gas- it's a problem- it's intended to route gas vapours from the tank into the combustion chamber, it's not intended to deal with liquid fuel.
If you're overfilling the gas tank frequently try this filling method:
FAQ: How can I avoid overflowing the gas tank?
Good luck with it!