ORIGINAL: Stickbuilder
That line with the fill plug in place appears to be the filler line to the tank. I think that you need a vent to the tank to keep vacuum from overcoming the pressure-pulse pump's ability to draw fuel. On non pumped engines, that is accomplished by the line from the muffler. Did you completely tear your carb down? If not, you may have a piece of trash hiding under one of the needles. I had a supertiger 90 several years ago that would starve itself for no explainable reason. Finally after about the 10th tear-down I found a very small grass seed hiding in the High speed needle spray bar.
Yes I did tear the carb, and found nothing at least that I could see, as for the line in question with the plug, I normally take the plug out to fill, the tank has a separate Easy Fueler Valve, mounted with the yellow bracket in picture. the thing is it runs great from mid TX throttle to WOT, but wont run lower past the mid throttle to Idle. It ran about 3 full tanks, till it ran out fuel. There must be some adjustment for lower speed and Idle??? And yes I think your right about the tank needing a vent line to prevent a vacuum, there is nothing on the muffler to attache this line, the hole has been replace with a screw. I have not tried since the weekend, trying to figure out what I can adjust or look into.
Again Thanks for your help, If you think of anything else, I would appreciate any additional Info.
roltech