1. GENERAL INFORMATION MXU 250R/300R POOR PERFORMANCE (AT HIGH SPEED) Inspection/Adjustment Symptom Probable Cause Check ignition timing Faulty ignition unit Correct timing Incorrect timing Faulty pulser coil Check valve clearance Improperly adjusted valve Correctly adjusted Incorrectly adjusted clearance Worn valve seat Check fuel pump for fuel supply Empty fuel tank Clogged fuel tube or filter Fuel flows freely Fuel flow restricted Clogged Fuel tank cap breather Check carburetor jets hole for clogging Not clogged Clogged Clean and unclog Check valve timing Correct Incorrect Cam timing gear aligning marks not aligned Check valve spring tension Not weakened Weak spring Faulty spring 1-26