Yamaha MX825V Service Manual

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SERVICE MANUAL

MX800V

MX825V

7UC-F8197-E0LIT-19616-02-50

2017.10×1

7UC-F8197-E0_Hyoshi.indd 1-2 2017/10/27 13:08:23

Default Chapter5
- Default Chapter5
  - How to Use this Manual5
- General Information7
  - Table of Contents8
Machine Identification11
- Serial Number11
- Starting Serial Number11
Dimensions12
- Top12
- Mounting Base12
- Rear13
- REAR (for Models Equipped with a Muffler)13
- Right Side14
- RIGHT SIDE (for Models Equipped with a Muffler)14
Important Information15
- Preparation for Removal and Disassembly15
- Caution on Service15
- Notes on Service15
- All Replacement Parts16
- Gaskets, Oil Seals, and O-Rings16
- Bearings and Oil Seals17
Basic Service Information17
- Electrical System17
Special Tools and Testers20
- Periodic Checks and Adjustments21
Introduction21
Maintenance Intervals Chart21
Periodic Maintenance/Lubrication Intervals21
Periodic Maintenance22
- Spark Plugs22
- Muffler23
- (For Models Equipped with a Muffler)23
- Engine Oil Leakage24
- Engine Oil Level25
- Replacing the Engine Oil26
- Fuel Leakage28
- Fuel Filter28
- Oil Cooler29
- Air Filter Element29
- Adjusting the Valve Clearance29
- Cylinder Heads Decarbonization33
- Engine Speed34
- Adjusting the Engine Speed35
- LOW ENGINE SPEED (Replace the Carburetor Assembly)36
- Fittings and Fasteners37
- Engine39
Engine Inspection39
- Measuring the Compression Pressure39
Air Filter41
MUFFLER (for Models Equipped with a Muffler)42
Oil Cooler43
- Removing the Oil Cooler44
- Checking the Oil Cooler44
- Installing the Oil Cooler44
Rectifier/Regulator46
Case and Fan47
- Removing the Case and Fan48
- Checking the Case and Fan49
- Installing the Case and Fan49
Tci Units, Flywheel and Stator Coil Assembly51
- Tci Units51
- Flywheel and Stator Coil Assembly52
- Removing the Flywheel and Stator Coil Assembly53
- Checking the Flywheel and Stator Coil Assembly54
- Installing the Flywheel and Stator Coil Assembly54
- Installing the Tci Units56
Cylinder Head Covers, Cylinder Heads57
- Cylinder Head #157
- Cylinder Head #259
- Checking the Rocker Arms and Rocker Arm Shafts61
- Checking the Push Rods61
- Removing the Cylinder Heads61
- Checking the Cylinder Heads61
- Installing the Cylinder Head Assembly62
Valves64
- Removing the Valves and Valve Springs65
- Checking the Valves and Valve Springs65
- Checking the Valve Seats67
- Valve Lapping68
- Installing the Valves and Valve Springs69
Oil Pump70
- Disassembling the Oil Pump71
- Checking the Oil Pump71
- Checking the Relief Valve72
- Checking the Crankcase72
- Installing the Oil Pressure Switch72
- Assembling the Oil Pump73
- Installing the Crankcase Cover 274
Pistons, Camshaft, Crankcase, and Crankshaft75
- Crankcase75
- Pistons, Camshaft, and Crankshaft77
- Removing the Flyweight Shaft Assembly and Governor Fork78
- Disassembling the Flyweight Shaft Assembly78
- Checking the Flyweight Shaft Assembly78
- Assembling the Flyweight Shaft Assembly79
- Installing the Flyweight Shaft Assembly and Governor Fork79
- Removing the Camshaft and Valve Lifters80
- Checking the Camshaft80
- Checking the Valve Lifters81
- Checking the Reed Valve82
- Installing the Valve Lifters and Camshaft82
- Installing the Cover 182
- Installing the Cover 283
- Checking the Crankcase Cover 183
- Installing the Crankcase Cover 184
- Checking the Cylinders and Pistons84
- Checking the Crankcase86
- Checking the Piston Pins86
- Checking the Piston Rings86
- Checking the Crankshaft88
- Checking the Connecting Rods Oil Clearance89
- Installing the Pistons and Piston Rings90
- Installing the Crankshaft91
Fuel Pump95
- Checking the Fuel Pump96
- Fuel95
Carburetor Assembly97
- Removing the Carburetor97
- Disassembling the Carburetor98
- Removing the Carburetor Assembly99
- Checking the Carburetor Assembly99
- Installing the Carburetor Assembly99
Intake Manifold101
- Removing the Intake Manifold102
- Checking the Intake Manifold102
- Installing the Intake Manifold102
Circuit Diagram104
- Electrical104
Electrical Components106
- Checking the Switch Continuity108
- Checking the Oil Pressure Switch108
- Checking the Tci Unit Resistance108
- Notice108
- Checking the Ignition Spark Gap109
- Checking the Spark Plug Caps110
- Checking the Stator Coil Assembly110
- Checking the Rectifier/Regulator111
- Checking the Starter Motor Operation111
Electric Starting System113
- Removing the Starter Motor113
- Disassembling the Starter Motor114
- Checking the Armature Coil115
- Checking the Brush116
- Checking the Starter Relay116
- Assembling the Starter Motor116
- Troubleshooting119
Engine Does Not Start119
- Ignition System119
- Electric Starting System120
Other Troubles121
- Engine Starts but Stalls121
- Engine Speed Does Not Increase122
- Engine Speed Is Uneven123
- The Battery Is Not Charged124
- Governor Operation125
Oil Pressure System126
- Specifications127
General Specifications127
Maintenance Specifications129
- Engine129
- Electrical133
Tightening Torques136
General Torque Specifications136
Lubrication Points and Type of Lubricants137
Wire Routing Diagram138
- Upper Side View138
- Left Side View142
- Right Side View144
- Rear Side View150

Questions and Answers:

J
Joseph TaylorAug 5, 2025
What to do if my Yamaha MX825V does not start?
- A
  Angel GloverAug 6, 2025
  If your Yamaha Engine won't start, several things could be the issue. First, ensure the battery terminals are clean and the battery is fully charged; if not, recharge or replace it. Next, check the spark plugs; they may need re-gapping or replacement. If the spark plugs are fine, inspect the spark plug cap and replace it if necessary. If the ignition spark gap is okay, the ignition system is likely functioning correctly. Also, consider replacing the TCI units or the main switch. Finally, make sure the ignition system's wiring is properly connected or repaired.