2004-2009 Honda TRX450R/TRX450ER Service Manual, Page 477Get this manual
IGNITION SYSTEM (After '05) REPLACEMENT Remove the carburetor from the engine (page 8-7)Remove the screw, throttle position sensor and 0ringI THROTTLE POSITION SENSOR
Install new O-ring and the throttle position sensor by aligning the tabs of the throttle position sensor with the flat side of the shaft as shownAlign