Yamaha MX250 - Page 3

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MX250, MX300

SERVICE MANUAL

Corporation, U.S.A.

1st Edition, March 2017

unauthorized use without the written

permission of Yamaha Motor

Corporation, U.S.A.

is expressly prohibited.

LIT-19616-02-45

Main Page

Table of Contents8
General Information11
Machine Identification11
Serial Number11
Starting Serial Number11
Dimensions12
Dimension Chart12
Top13
Mounting Base13
Left Side14
Front15
Important Information16
Preparation for Removal and Disassembly16
Caution on Service16
Notes on Service16
All Replacement Parts17
Gaskets, Oil Seals, and O-Rings17
Bearings and Oil Seals18
Basic Service Information18
Electrical System18
Special Tools and Testers22
Periodic Checks and Adjustments23
Introduction23
Maintenance Intervals Chart23
Periodic Maintenance/Lubrication Intervals23
Periodic Maintenance25
Spark Plug25
Fuel Leakage26
Engine Oil Leakage26
Engine Oil Level26
Replacing the Engine Oil27
Air Filter Element28
Muffler29
Fuel Tank Filter31
Fuel Cock Strainer32
Breather Hose33
Cylinder Head Decarbonization33
Adjusting the Valve Clearance33
Engine Speed35
Adjusting the Engine Speed36
Recoil Starter37
Fittings and Fasteners38
Engine39
Engine Inspection39
Measuring the Compression Pressure39
Air Filter41
Fuel Tank42
Checking the Fuel Tank Cap (Canister)43
Muffler44
Installing the Muffler45
Recoil Starter46
Disassembling the Recoil Starter47
Checking the Recoil Starter47
Assembling the Recoil Starter48
Flywheel50
Removing the Flywheel51
Installing the Flywheel52
Installing the Tci Unit52
Governor54
Throttle Lever Assembly54
Flyweight Shaft Assembly55
Removing the Flyweight Shaft Assembly and Governor Fork56
Disassembling the Flyweight Shaft Assembly56
Checking the Flyweight Shaft Assembly56
Assembling the Flyweight Shaft Assembly57
Installing the Flyweight Shaft Assembly and Governor Fork57
Adjusting the Governor58
Engine Switch and Oil Warning Unit59
Cylinder Head Cover, Cylinder Head60
Checking the Rocker Arm62
Checking the Push Rod62
Checking the Cylinder Head62
Installing the Cylinder Head Assembly63
Valve64
Removing the Valves and Valve Springs65
Checking the Valves and Valve Springs65
Checking the Valve Seats67
Valve Lapping68
Installing the Valves and Valve Springs69
Piston, Camshaft, Crankcase, and Crankshaft70
Removing the Camshaft and Valve Lifter72
Checking the Camshaft72
Checking the Valve Lifter73
Installing the Valve Lifter and Camshaft74
Checking the Crankcase Cover74
Installing the Crankcase Cover74
Checking the Cylinder and Piston75
Checking the Crankcase76
Checking the Piston Pin77
Checking the Piston Rings77
Checking the Crankshaft79
Checking the Connecting Rod Oil Clearance79
Installing the Piston and Piston Ring80
Installing the Crankshaft81
Removing the Carburetor83
Disassembling the Carburetor84
Checking the Carburetor85
Electrical86
Circuit Diagram86
Electrical Components88
Checking the Switch Continuity89
Checking the Ignition Spark Gap89
Checking the Spark Plug Cap Resistance90
Checking the Air Gap91
Checking the Ignition Coil (Tci Unit, Primary) Resistance91
Checking the Ignition Coil (Tci Unit, Secondary) Resistance92
Checking the Engine Switch93
Checking the Oil Level Switch93
Checking the Wire Harness94
Troubleshooting95
Engine Does Not Start95
Engine Starts but Stalls96
Engine Speed Does Not Increase97
Engine Speed Is Uneven98
Governor Operation99
Specifications101
General Specifications101
Maintenance Specifications103
Engine103
Electrical107
Tightening Torques110
General Torque Specifications110
Lubrication Points and Type of Lubricants111
Wire Routing Diagram112
Upper Side View112
Engine Switch and Oil Warning Unit114
Tci Unit116
Oil Level Switch (Crankcase Cover)118

Yamaha MX250 - Page 3

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