verslagen1 wrote on 08/07/08 at 11:31:24:..........
2nd... dirt or other blockage in the screens. 2 places to check, remove the petcock from the tank (empty tank) and check the screen for debree and varnish. Also, there's a screen on the float valve. you need to diassemble the carb to get at it.
So, I don't have a petcock assembly in hand and it's been a year since I did..... Doesn't the PRI fuel path run thru the RES port in the tank??? Wouldn't the screen be clogged for both?? And, the tiny screen on the carb by the float, wouldn't that cause same issue in PRI too???
Sounds like a Vacuum issue, but why??? If the diaphram in the petcock was bad, I think the issue would be flooding not starving for fuel...... If you had a vac leak somewhere else then WOT would cause weak vac at the Petcock.
Here is a test to check for vacuum leak. Start the bike. Then while idling, spray WD40 around the rubber intake manifold and the other misc spots on the carb (and Petcock?). If the idle changes you found a leak. Once fixed, buy some engine degreaser and clean up. NOTE: You could use carb cleaner but that can damage some paints.
EDIT: just remembered someone previously said to check all the tank & Carb vents. The idea was that, at speed, the restricted vents would not allow fuel into the carb fast enough..... but I think that would also be one of the "would also be noticed in PRI"