Motorcycle Repair: gs450t parallel twin, tight seals, vacuum lines

Question
My bike starts and idles great. Once you ride off it sputters out like its out of gas after about two to three minutes. I removed the internal peices of the gas cap to make suree it was venting. I installed a new diaphragm in the petcock pump, insuring tight seals on my vacuum lines. I checked the valve clearance. The plugs are bone dry. I also installed new intake o rings. What gives?

Answer
Joseph,

-Is it getting a good supply of fuel to the carbs?
-Can you open the drain screws on the carbs and check for fuel?
-If both cylinders are quitting, I suspect
a problem with the fuel getting to the carbs.
-Have the carbs been cleaned?
-Make sure the petcock lines are on correctly.
Some petcocks have 4 lines, two from the
tank, one fuel line to the carbs and the vent
or vacuum line from the carb.
-If only one cylinder quits, it could be
a bad carb float or float valve.
-do you have a fuel filter?
-when it quits, check for spark just in case
it is not a fuel problem.
-try some wd-40 in the carb mouth and see
if it fires. If it does you know the fuel is
lacking.