Motorcycle Repair: Fuel Problems, pet cock, vacuum gas

Question
I have a 1991 KAWASAKI EX500.  I need to know 2 things. First I took an MSF course and the say to turn your fuel supply to off. I did but found it to be PRIME. Is this the off position or to Prime ie. to add more fuel to the carbs for starting.  And two I believe that I have varnishing and gumming in my carbs.  Is the use of Berryman Carb cleaner a bad idea or will it do damage to any part of the carbs or engine?

Answer
On the pet-cock there is not an OFF postion's. Under the gas tank its self you will find where you can turn the gas on and off. you almost have to remove the gas tank to get to it.. Prime does not dump more gas it just never stops dumping the gas for you, The ex500 is a vacuum gas line. So untill the bike is running the carbs will not pull gas from the tank. Thats why you have the prime there. And the best way to clean a carb is to take it apart, if you have build up are dirt sand etc... etc... a carb cleaner liquid is not going to help.. Hope that helps you