5. FUEL SYSTEM MXU 300/250 Spring Remove the spring from the throttle valve Throttle Valve Needle Retainer Pry off the needle retainer and remove the jet needle. Check the throttle valve and jet needle for wear or damage. ASSEMBLY Reverse the "DISASSEMBLY" procedures. Jet Needle Clip Groove Install the throttle valve into the carburetor body. Align the groove in the throttle valve with the throttle stop screw on the carburetor body. Throttle Stop Screw 5-8