Kymco Maxxer/Mongoose 250/300 ATV Repair Manual, 2005

This Kymco factory service manual (manual reference 4122-ATV250-S00, First Edition, June 2005) covers the Maxxer/Mongoose 250 (LA50) and 300 (LA60) ATV family. The LA50 specification section also lists the MXER 250R.

PDF Search, Wiring Detail and Page Count

Search and diagram navigation: Most service text is searchable, but the maintenance-table image and wiring-diagram contents are not text-searchable. There are no embedded PDF bookmarks. Small wiring labels require zooming.

The ZIP download contains one printable, English-language PDF with 251 pages, including the original cover and front matter, one additional photo page, and one additional color wiring diagram.

Powertrain Repair and On-/Off-Road Electrical Coverage

The coverage highlights below are a selection from the manual’s 20 chapters. Additional topics include frame-cover and exhaust-muffler removal.

• Engine repair: Engine removal and installation, cylinder-head service, crankcase separation, crankshaft inspection, and balance-shaft timing.

• CVT and reverse drive: Drive-pulley and clutch disassembly, driven-pulley bearing replacement, reverse-gear inspection, and transmission reassembly.

• Fuel and lubrication: Carburetor disassembly, float-level inspection, fuel-valve service, oil-strainer cleaning, and oil-pump inspection.

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

• Brakes and chassis: Hydraulic brake bleeding, master-cylinder and caliper repair, wheel-hub service, suspension inspection, and steering adjustment.

• Electrical diagnosis: Charging, ignition and starting-system tests, troubleshooting charts, cable/harness routing, and separate on-road and off-road wiring diagrams.

This manual suits technicians familiar with engine disassembly and electrical testing who have access to the specified measuring equipment and special tools.

Engine Measurement and Compression Diagnosis

Step-by-step procedures cover camshaft-holder disassembly, valve and valve-guide inspection, cylinder/piston measurement, and piston-ring service. Cylinder-head and cylinder/piston work can be performed with the engine installed; crankcase separation for crankshaft service requires engine removal.

Compression references: The model-specific tables list 15 kgf/cm² for the 250 and 16 kgf/cm² for the 300, while the general Chapter 3 compression-test page prints 16 kg/cm². The model-specific references and the Engine Will Not Start or Is Hard to Start chart help distinguish fuel, ignition and mechanical causes before engine disassembly.

Piston installation coverage addresses ring-mark orientation and 120° end-gap staggering, with cautions about breaking the rings during cylinder installation.

CVT Components and Reverse Transmission

Drive-pulley inspection includes the weight rollers, movable drive face and collar. Clutch/driven-pulley service extends to the clutch outer, linings, bearings, seals and spring assembly, with belt-width wear limits supplied for inspection.

The CVT chapter requires a clutch spring compressor to prevent spring damage and warns against oil or grease on the belt, pulley faces or clutch linings.

Transmission repair reaches the main and counter axles, reverse wheel gear and clutch dog. Shift-fork, shift-cam, guide-bar and primary-drive-axle inspection are also included. Transmission service can be performed with the engine installed.

Carburetor, Lubrication and Cooling Service

Carburetor procedures cover the throttle valve, jets, air cut-off valve and float assembly. Oil-pump inspection includes rotor clearances, while lubricant specifications distinguish normal changes from disassembly fills: SAE 90 gear oil capacity is 300 cc at a change and 400 cc at disassembly.

Cooling access: Water-pump service requires engine removal; other cooling-system work can be performed in-frame. Mechanical-seal replacement includes the associated seal washer and pump-shaft bearings.

Cooling specifications distinguish the 1.1 L radiator and 0.3 L reserve tank within the 1.4 L total capacity. Radiator-cap testing and thermostat/thermosensor checks support diagnosis of overheating and incorrect temperature indications.

Brake Hydraulics, Wheel Hubs and Steering

Brake procedures distinguish the handlebar-operated rear master cylinder from the rear-pedal master cylinder and cover the rear caliper’s separate hydraulic connections. DOT 4 fluid specifications accompany the bleeding procedures.

Rear-caliper disassembly cautions address gradual air pressure, cylinder-bore damage and replacement of removed piston and dust seals.

Chassis coverage includes wheel-hub bearing replacement, tie-rods and ball joints, steering-column service, rear axle/hub disassembly and swing-arm inspection. Adjustment sections address drive-chain slack, toe-in and the drive-select linkage.

Charging, Ignition and Starting Tests

Electrical coverage includes charging limit-voltage/current tests, regulator/rectifier checks and A.C. generator resistance measurements. Ignition-unit/change-gear-control tables are referenced to the YF-3501 Electric Tester; CDI tester results and ignition-coil/pulser-coil measurements are also provided.

Starter diagnosis extends to motor continuity, brush wear limits, relay operation and the one-way starter clutch.

Circuit documentation: Cable & Harness Routing, Charging Circuit, Ignition Circuit (On Road) and Starting Circuit views accompany the system tests. The Wiring Diagram: Off Road Type is paired with an on-road sheet; instrument, horn, position-light and turn-signal service are marked on-road only.

Maintenance Planning and Workshop Tools

The maintenance schedule uses an initial 100 mi/150 km/1-month point, followed by 600 mi/1,000 km/6-month and 1,200 mi/2,000 km/12-month intervals. Air-filter service is specified every 20–40 hours, with coolant replacement every 24 months.

Named tools include Flywheel Puller E003, Tappet/Valve Adjuster E012, Valve Spring Compressor E040, Oil Seal and Bearing Installer E014, Universal Holder E017, rear-axle Nut Wrench F010, and tie-rod/ball-joint removers F011/F012.

For actual service, follow the manual’s precautions for gasoline, battery electrolyte, hot pressurized coolant, hydraulic brakes, rotating components, and securely supporting the ATV during chassis work.

Selected Idle, Valve-Clearance and Cooling Test Values

The carburetor adjustment procedures specify warm-engine idle speeds of 1,500 ±100 rpm for the 250 and 1,600 ±100 rpm for the 300. Intake and exhaust valve clearance is 0.1 mm (0.004 in) with the engine cold.

Radiator-cap inspection specifies a relief-pressure range of 0.75–1.05 kgf/cm² (75–105 kPa). The cooling-system test section also identifies the pressure limit needed to avoid damaging the radiator and hose connections.