I've been having fuel issues at high rpm usually when my rake is less full but it has gotten worse. Around 8-9k I feel that I'm losing power and I have to twist the throttle harder to go the same speed until I pull over and use res and choke to start back up then it goes away and I fill up and it doesn't happen for a bit. I did have two bends in the fuel line from tank to the t joint. Changed that haven't tested it. Could it be the petcock screen is clogged?

 

There is the great chance of sediment or rust in the bottom of your tank. I have a couple Vintage bikes and if you get to certain point it all collects at the bottom clogging the petcock filter. Plus I HIGHLY recommend that your fuel line is not pinched either. At high RPM's if you do have a pinch only a limited amount of fuel can flow to the carbs. Drain the tank and clean the screen and refill with fresh gas. I suggest pouring the fuel into a clean white bucket to see how bad the debris really is and points you faster in the right direction. Then if need be get new fuel lines and make sure there isn't any pinches or debris clogging those. Limited fuel amount will choke the engine to limited/lower RPM's. I suggest starting with the petcock first.

 

Fixed the fuel line put on 200 miles since ran the bike hard I've had no problems since. When I got the fuel deprived feeling today it wasn't at 3/4 of a tank it was actually when I needed gas. Noticed a lack of power when my girls on back it was hard doing 125. But alone I got her up pretty quick seems fine. The old fuel line had two 45 degree bends