Houston we have a problem.  The bike idles fine and runs great up to about 130 - 140k, then it surges like it's running out of fuel.  If you never take it past 120, it'll run all day long without the slightest hesitation, however if you take it up to 140 and then back down to even 110 it surges from then on.  When we first brought it home we got 10 miles down the highway and the little sucker stalled and wouldn't start without the choke.  After some investigating we discovered a kinked tank vent line so that solved that but she still has this surging problem.  We took the tank off and cleaned it, cleaned the lines, made sure there was fuel running out the bottom of the carbs, cleaned the petcock,  ran a couple of tanks of carb cleaner through it and still it surges on the top end.  Before we bought it design cycle set the valves, synced the carbs, and did a tune up so I don't know what to think. :dunno:  Oh by the way, this is a 92 cbr 600 with 24000k and it has no fuel pump.  Anybody have any ideas?????