Motorcycle Repair: Fuel Tank Pressure - Fuel Overflow Problem., softtail custom, overflow tube

Question
I have a 1998 Softtail Custom that I had installed a 42 MM Mikuni Carb about 2 years ago.  Just recently, when I get gas, I get fuel vapor pressure escaping from the gas tank when I loosen the gas gap.  It never did this before (over 15K miles on new carb).  I did not bother me much until yesterday when I came home and parked the bike in my garage with only about 1 gallon of gas in the tank (had run about 170 miles since last refill).  The Carb was profusely leaking gas out of the overflow tube.   When I opened the gas cap pressure was relieved and the overflow stopped.

I looked at my service manual and discovered that there is a solenoid valve that opens to suck vapors from the tank into the carb intake to burn the vapors when the bike is running.  Could this solenoid be bad?  Can I just bypass the solenoid operation and normally let the pressure flow to the carb with any performance issues?
I believe in not polluting the environment, but I presume every time I open the gas cap, I am leaving some fumes into the environment.  It would be probably a lot less that about a quart of fuel that spilled from the overflow yesterday.
Thanks for your help in advance...  Mark Harley!


Answer
If you have a California model then you will have a vapor valve. If not then its vented to the air. Its either vented through a vent line attached to the tank or through the gas cap. If you have duel gas caps then just one is the vent. If your gas caps are the vent then the vent one is probably stuck in the close position
Good luck and happy riding
Mike