Another thing that can make a bit of a difference is the fuel line you are using. I have used several different brands and most seem to have more slip on the copper/brass tube than what I like. I really liked Prather fuel tubing. It was pinkish in color and held a good grip on copper/brass tubing. Between this fuel tubing and the brass barbs, no more problems! I was bummed when the Prather brand went away until I found who has it available now. I purchased a full spool of it an am happy, happy, happy.
Here is where to get the good stuff:
http://hyperprod.bizhosting.com/prather_fuel_tube.html
Dan