look in the gas tank there is a screen on the pickup in the tank may have junk on it.wash and blow out all carb parts with air you may have a air bleed plugged i wash the card with paint thinner and let some parts swim in it for over nigth the metering needles where the set up springs are they are on power valve bodys the bodys may be sticking in the well have seen this take out wash and you may have to used a fine 3m gray pad on the bodys