Fuel Issue

[Jay Loeppke]

My Son took my bike up to school for a month, when he got there  
(260M),  and shut it off he had a tough time starting it again and  
keep  running unless the choke was on or on prime.  He said if he  
takes it (the petcock) off prime he can watch the gas drain out of my  
little clear fuel filter.  It doesn't help to open the tank, so no  
vapor lock. all the CA stuff has been removed long ago.   Just did a  
200m ride this last weekend with no problems.  I am thinking a vacuum  
leak of some sort.  Rebuild the petcock?  Has Any body done away with  
the vacuum on the petcock?  I did it to my KLR 650, runs great