A few days ago I read a thread on here about this problem. Just installed the pumper on my 650r, had rode it once. Took off the tank and sure as heck the front corner of the carb was rubbing against the tank. Some guys turn the carb a little off center so it dosen't rub but that puts the a/p screw real close to the header. I took a file to the corner - just rounded it off and smoothed it out a bit - problem solved. If you have installed a pumper on your pig you might want to make sure this isn't happening to your tank.