2004–2005 KYMCO MXU 250 ATV Service Manual

This KYMCO factory service manual covers the 2004–2005 MXU 250 (LB50AD/AA), with its liquid-cooled 4-stroke O.H.C. engine and automatic centrifugal drive system.

Supplied as one 276-page PDF in English.

• Engine repair: Engine removal, cylinder-head and piston disassembly, crankshaft and balance shaft inspection, valve timing, and valve-clearance adjustment.

• CVT and transmission: Drive and driven pulley service, clutch overhaul, drive-belt inspection, final reduction repair, and reverse-gear and shift-mechanism inspection.

• Fuel system: PTG carburetor rebuilds, float-level inspection, air cut-off valve service, and PAIR solenoid valve removal and installation.

• Cooling system: Radiator and cap pressure testing, thermostat and thermosensor checks, mechanical water-pump seal replacement, and coolant replacement and bleeding.

• Brakes and chassis: Master cylinder and caliper repair, hydraulic brake bleeding, front suspension and rear fork service, steering column inspection, and toe-in alignment.

• Electrical diagnosis: Charging-system tests, ignition-unit and change-gear-control checks, starter-circuit troubleshooting, and separate Off Road and On Road wiring diagrams.

This manual suits mechanics who can interpret electrical test results and carry out internal engine measurements using the specified workshop tools.

Engine Repair and Maintenance

Chapters cover frame cover and exhaust muffler removal, followed by internal engine inspection and assembly. The manual distinguishes cylinder-head and piston work that can be done in the frame from crankcase separation for crankshaft service, which requires engine removal.

Maintenance schedule charts and lubrication point views accompany torque tables, fluid-capacity data, cylinder-compression checks, spark plug specifications, and component wear limits. Valve spring compressor E040 and tappet adjuster E012 are identified for the cylinder-head and valve procedures.

CVT, Final Reduction and Rear Drive

Drive and driven pulley coverage extends to weight rollers, clutch shoes, driven-face bearings, and assembly alignment. The transmission chapter details the reverse wheel gear, clutch dog, shift fork, shift cam, and speedometer gear.

Rear-drive sections cover axle and hub disassembly, bearing and seal replacement, sprocket inspection, and drive-chain adjustment. Rear fork procedures include pivot, bushing, and side-play checks.

Carburetor and Secondary Air System

PTG carburetor repair covers the throttle valve, jets, float valve, and air cut-off diaphragm, with troubleshooting for rich or lean running. The PAIR secondary-air section identifies the solenoid valve and its hose connections.

The carburetor notes warn that forcing the air screw against its seat can damage the seat.

Water Pump and Cooling-System Tests

Water-pump service includes mechanical seal, seal washer, shaft, and bearing replacement, supported by a labeled assembly view. The chapter specifies engine removal for water-pump service; other cooling-system work can be performed in the frame.

Radiator pressure-test instructions warn that excessive test pressure can damage the radiator and hose connectors.

Hydraulic Brakes, Steering and Suspension

The brake chapter distinguishes the rear brake's left-hand lever master cylinder from its pedal-operated master cylinder, with service information for both. Front suspension coverage includes ball-joint removal with tool F012, tie-rod adjustment, and steering column bearings.

Always verify the factory specifications and follow the shop safety precautions, especially when supporting the ATV or servicing hydraulic brakes.

Electrical Tests and Circuit Diagrams

The Off Road and On Road diagrams distinguish the lighting and switch layouts, including on-road turn signals, horn, and license light. Together with the Charging Circuit, Ignition Circuit, and Starting Circuit schematics, they help match fault tracing to the vehicle's electrical equipment. Cable and harness routing views show component connections and wire paths.

Troubleshooting flowcharts address hard starting, loss of power, poor charging, and no spark. Ignition-unit and change-gear-control resistance tables specify a YF-3501 tester; the manual warns that an unsuitable tester can produce misleading readings.

Starter repair covers motor disassembly and starter clutch inspection. Recoil starter coverage focuses on rope replacement and ratchet checks, with a warning against dismantling the starter assembly.

PDF Search, Bookmarks and Diagram Readability

The page total includes all 19 chapter contents pages and diagrams; there are no separate cover sheets or supplements. The main text is searchable, but the wiring-diagram labels and some tables are not; 19 chapter bookmarks use Italian file-name labels. Small labels in the Off Road diagram require zooming, and some On Road wire codes remain blurred when enlarged.