I agree Dave, it definately appears to be losing fuel, which means either clunk coming out of fuel, which isn't happening, or the tank is losing pressure. I checked the sil. lines from tank to engine, (pulled them off, plugged one end and blew into the hose while stretching it.. no loss of pressure).. I did pull the nipple and made sure it was open. Everything looked great. I also blew through it and there didn't seem to be any difference in flow between blowing through a straight piece of tubing and the the same tubing attached to the pressure fitting. I have not drilled it out further, which is something I can try, but i don't understand why it would have suddenly changed... Yes, it was a Fox plug originally, but I replaced it with the idle bar plug just in case (figured it might help since the jug is inverted).... You really think swinging at 11700 is lugging? I figured around 12000 was pretty optimal???

There is one other thing I found that I have not tested yet. Though the motor seemed to run perfectly at both hs and ls, according to the manual that came with the engine, for tuning the ls needle the "starting position" that is supposed to be close is with 3/32" between the needle and the spraybar. Mine was set at about 1/64"... It didn't seem to be running too lean, but I've backed it out to about 3/32" and will try adjusting it from there and see if that makes a difference.