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Yamaha MX800V EFI Engine

General Technical Data

Yamaha MX800V Engine Specifications

Engine Model ................ Yamaha MX800V-EFI
Engine Type ................ 4-cycle OHV V-twin cylinder air-cooled gasoline engine
Number of Cylinders ................ Two
Displacement, cu.in (cc) ................ 50.3 (824)
Cylinder Bore, in (mm) ................ 3.15 (80.0)
Piston Stroke, in (mm) ................ 3.23 (82.0)
Rated Engine Power, hp (kW) ................ 31.6 (23.6)
Rated Engine Speed, rpm ................ 3600
Maximum Torque, Nm (ft-lbs) ................ 65.3 (48.2)
Torque Speed, rpm ................ 3100
Compression Ratio ................ 9.1:1
Cylinder Liner ................ Cast iron
Valve Arrangement ................ Overhead valve
PTO Shaft Rotation ................ Counterclockwise (from PTO shaft side)
Lubrication System ................ Full pressure with filter
Cooling System ................ Forced air
Air Cleaner Type ................ Dual dry element
Oil Filter Type ................ Cartridge
Ignition System ................ ECU control battery ignition
Starting System ................ Electric starter

Fuel System

Fuel System Type ................ Carburetor
Carburetor Model ................ Delphi Multec EFI
Governor Type ................ Centrifugal, flyweight
Fuel Pump Type (Lo) ................ Mechanical
Fuel Pump Type (Hi) ................ Electrical
Fuel Type ................ Gasoline (86 or higher)
Fuel Line Pressure, psi (bar) ................ 37-41.5 (2.6-2.9)

Dimensions and Weight

Overall Length, in (mm) ................ 19.7 (499)
Overall Width, in (mm) ................ 18.2 (463)
Overall Height, in (mm) ................ 25.2 (639)
Dry Weight, lbs (kg) ................ 131.8 (60.0)

Yamaha MX800V Maintenance Data

Service Data

Cylinder Compression, psi (bar) ................ 190-210 (13.1-14.5)
Cylinder Bore Inside Diameter (Max), in (mm) ................ 3.1555 (80.150)
Cylinder Head (Max. Out of Flatness), in (mm) ................ 0.004 (0.10)
Intake Valve Clearance, in (mm) ................ 0.003-0.005 (0.07-0.13)
Exhaust Valve Clearance, in (mm) ................ 0.003-0.005 (0.07-0.13)
High Idle Speed (No load), rpm ................ 3550-3600
Low Idle Speed (No load), rpm ................ 1450-1550

Engine Oil and Filter

Engine Oil Type ................ Yamalube, SAE 10W, SAE 10W-30, 10W-40
API Service Classifications ................ SE, SF, or higher
Oil Capacity, qts (L) ................ 2.12 (2.0)
Air Filter Element Part Number ................ 7UD-E4461-00
Air Filter Inner Element Part Number ................ 7UD-E4451-00
Engine Oil Filter Part Number ................ 7UD-E3440-00
Fuel Filter Part Number ................ 7UD-F4502-00

Ignition System

Spark Plug Type ................ NGK BPR6ES
Spark Plug Gap, in (mm) ................ 0.028-0.032 (0.70-0.80)
Ignition Timing, degrees ................ 30 BTDC
Spark Plug Torque, Nm (ft-lbs) ................ 20 (14)

Service Intervals

Check Engine Oil Level ................ Every 10 hours
Service Air Filter Element ................ Every 50 hours
Clean and Adjust Spark Plug ................ Every 100 hours
Change Engine Oil ................ Every 100 hours
Check and Change Fuel Filter ................ Every 100 hours
Replace Engine Oil Filter ................ Every 200 hours
Clean Oil Cooler Fins ................ Every 200 hours
Check Fuel Line ................ Every 200 hours
Clean Fan Case Covers and Cooling Area ................ Every 200 hours
Replace Air Filter Element ................ Every 250 hours
Replace Spark Plug ................ Every 250 hours
Service Air Filter Inner Element ................ Every 250 hours
Replace Air Filter Inner Element ................ Every 500 hours
Check and Adjust Idle Speed ................ Every 1000 hours
Check and Adjust Valve Clearance ................ Every 1000 hours
Clean Combustion Chamber ................ Every 1000 hours

Yamaha MX800V Service Specifications

Cylinder Head And Valves

Cylinder Head Flatness, in (mm) ................ 0.002 (0.05)
Valve Head Diameter (Intake), in (mm) ................ 1.0984-1.1063 (27.9-28.1)
Valve Head Diameter (Exhaust), in (mm) ................ 1.3740-1.3819 (34.9-35.1)
Valve Stem Diameter (Intake), in (mm) ................ 0.2342-0.2348 (5.948-5.963)
Valve Stem Diameter (Exhaust), in (mm) ................ 0.2339-0.2344 (5.940-5.955)
Valve Stem Lenght (Intake), in (mm) ................ 3.4961 (88.8)
Valve Stem Length (Exhaust), in (mm) ................ 3.5354 (89.8)
Valve Seat Width, in (mm) ................ 0.0354-0.0433 (0.9-1.1)
Valve Guide Inside Diameter, in (mm) ................ 0.2362-0.2367 (6.000-6.012)
Valve Stem To Valve Guide Clearance (Intake), in (mm) ................ 0.0031 (0.08)
Valve Stem To Valve Guide Clearance (Exhaust), in (mm) ................ 0.004 (0.10)
Valve Spring Free Length (Intake), in (mm) ................ 1.4606 (37.1)
Valve Spring Free Length (Exhaust), in (mm) ................ 1.4016 (35.6)

Cylinder Block

Cylinder Inside Diameter, in (mm) ................ 3.1496-3.1504 (80.000-80.020)
Piston Skirt Diameter, in (mm) ................ 3.1480-3.1488 (79.959-79.980)
Piston Ring Groove Side Clearance (Top), in (mm) ................ 0.0016-0.0031 (0.04-0.08)
Piston Ring Groove Side Clearance (2nd), in (mm) ................ 0.0012-0.0028 (0.03-0.07)
Piston Pin Outside Diameter, in (mm) ................ 0.7478-0.7480 (18.995-19.000)
Clearance Between Piston And Cylinder, in (mm) ................ 0.0013-0.0019 (0.033-0.047)
Piston Ring End Gap (Top), in (mm) ................ 0.0079-0.0138 (0.20-0.35)
Piston Ring End Gap (2nd), in (mm) ................ 0.0079-0.0138 (0.20-0.35)
Piston Ring End Gap (Oil), in (mm) ................ 0.0079-0.0276 (0.20-0.70)
Connecting Rod Big End Inside Diameter, in (mm) ................ 1.5750-1.5756 (40.005-40.020)
Connecting Rod Small End Inside Diameter, in (mm) ................ 0.7483-0.7488 (19.006-19.020)
Crankpin Outside Diameter, in (mm) ................ 1.6122-1.6161 (40.950-41.050)
Crankshaft Big End Side Clearance, in (mm) ................ 0.0079-0.0256 (0.20-0.65)
Cam Height (Intake), in (mm) ................ 1.2947 (32.885)
Cam Height (Exhaust), in (mm) ................ 1.3369 (33.957)
Camshaft Journal Outside Diameter, in (mm) ................ 0.6679-0.6689 (16.965-16.990)

Tightening Torques

Cylinder Head Bolt (M10x1.25) ................ 50 Nm (36 lb-ft)
Cylinder Head Cover Bolt (M6x1.0) ................ 11 Nm (8.0 lb-ft)
Oil Drain Bolt (M12x1.5) ................ 27 Nm (20 lb-ft)
Air Filter Case Stay Bolt (M8x1.25) ................ 10 Nm (7.2 lb-ft)
Ignition Coil Bolt (M6x1.0) ................ 7 Nm (5.1 lb-ft)
Oil Cooler Bolt (M6x1.0) ................ 9 Nm (6.5 lb-ft)
Fan Case Bolt (M6x1.0) ................ 7 Nm (5.1 lb-ft)
Flywheel Nut (M22x1.5) ................ 180 Nm (130 lb-ft)
Crankshaft Position Sensor Bolt (M6x1.0) ................ 7 Nm (5.1 lb-ft)
Cylinder Air Shroud Bolt (M6x1.0) ................ 7 Nm (5.1 lb-ft)
Rocker Arm Shaft Bolt (M5x1.0) ................ 4.0 Nm (2.9 lb-ft)
Oil Pressure Switch (M4x0.7) ................ 8 Nm (5.8 lb-ft)
Oil Pump Cover Bolt (M6x1.0) ................ 10 Nm (7.2 lb-ft)
Relief Valve (M12x1.25) ................ 30 Nm (22 lb-ft)
Crankcase Cover Bolt (M8x1.25) ................ 30 Nm (22 lb-ft)
Connecting Rod Cap Bolt (M8x1.25) ................ 20 Nm (14 lb-ft)