My brother just bought a 1986 XR600RF. Motor 100% and no smoke. Was apparently recon (the gaskets does look new) recently. Bottom end revs good grunt. Problem is when holding the throttle open in higher gears you can feel something is holding "back". I did remove the air filter, and the "problem" worse then. We are about a 1000 meters above sea level. I've adjusted and set countless carbs before, but a twin carb setup on a single, never! Both carbs have 122 mains, with the second carb (right side) no secondary fuel jet. Should I "up" the mains? I'm 104kg, but expected a bit more poke from the bike. My 1992 Africa Twin will leave the XR for dead in any "roll on", in any gear. Bike starts easy. Timing seems OK. Any ideas anyone???