The 4 Cycle Ryobi S430 trimmer does not have a high speed carburetor screw, only an idle screw for adjustments to idle. The Ryobi factory sets the engine to run at a very low speed when at maximum throttle, probably to comply with emission standards. This means you don’t get the power you would expect from an engine this size. I called their tech support and they said this is set in the factory and the customer cannot adjust their own engine. The Ryobi 4 Cycle S430 is not worth the money. I regret my purchase.