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The power valve channel restrictors (arrows) are similar to the main jets that restrict the amount of fuel added when the power valve opens. This allows you to lean the primary jets and still have sufficient fuel when demand increases. If it's necessary to go to smaller primary jets for part-throttle tuning but you still need more the wide-open throttle fuel, compute the smaller jet flow area reduction, then enlarge the power valve channel restrictor by that area to add the fuel back in. The second pin indicates the position of the idle feed restrictor.