This is not true.
During a pinch test you want the engine to speed up slightly. This is a slightly rich setting and is desirable. If you pinch the fuel line and the engine stays the same or dies, it is on the lean side and should be richened a click or two.
ORIGINAL: nitrobasher
to make sure your settings are correct on the engine pinch the lines.. the motor should stay at the same rpms and then die... if it goes to higher rpms then dies im pretty sure its to lean?