I've heard that the pointed ends of the adjustment needles can break off and get stuck in the metering holes if they were closed over tightly and the carb was left to sit unused for any length of time with any amount of residual fuel left in it from the corosion caused by the methanol, would cause an over lean condition if you're opening them to just the typical number of turns, when a Tilly is lean, the motor rpms pick up just as it would do when it is running out of fuel....