Yamaha MX800V-EFI

The Yamaha MX800V-EFI is a small (824 cc, 50.3 cu-in) V-twin air-cooled four-stroke internal combustion gasoline engine with vertical shaft, manufactured by Yamaha.

The Yamaha MX800V-EFI motor has two-cylinder, overhead valves and a ball bearing supported P.T.O. The engine is equipped with an industry-standard air filtration system; electronic fuel injected system (Delphi Multec-EFI); ECU controlled electronic ignition coils and an electric starter.

The cylinder bore and the piston stroke is 80.0 mm (3.15 in) and 82.0 mm (3.23 in), respectively. The compression ratio rating is 9.1:1. The MX800V-EFI produces 31.6 PS (23.6 kW) at 3,600 rpm of maximum gross power or 31.0 HP (23.1 kW) at 3,600 rpm of gross rated power (SAE J1995) and 65.3 Nm (6.66 kg·m, 48.2 ft·lb) at 3,100 rpm of torque.

General information

Engine Specifications
Model	MX800V-EFI
Type	4-stroke, OHV, V-twin
Displacement	824 cm 3 (50.3 cu-in)
Max. horsepower	31.6 PS (23.6 kW) at 3,600 rpm
Max. torque (crank PTO)	65.3 Nm (6.66 kg·m, 48.2 ft·lb) at 3,100 rpm
Fuel system	Delphi Multec – EFI
Cooling system	Forced-air
Ignition system	ECU Controlled Electronic Ignition Coils
Lubricating system	Full pressure with filter
Starting system	Electric starter
Stoping system	Misfire
Fuel used	Unleaded gasoline (octane number 86 or higher)
Fuel tank capacity	–
Fuel consumption	–
PTO shaft rotation	Counterclockwise (from PTO shaft side)

Service Information

Engine
Maximum speed	3550-3600 rpm
Cylinder compression	13.4-14.8 kg/cm2 (190-210 psi)
Valve clearance
Intake valve	0.07-0.13 mm (0.003-0.005 in)
Exhaust valve	0.07-0.13 mm (0.003-0.005 in)
Oil system
Oil type	Yamalube 4-stroke or an equivalent (SE or higher)
Recommended oil	SAE 10W-30
Oil capacity	2.0 L (2.11 US qt, 1.76 Imp.qt)
Ignition system
Ignition timing	BTDC 30° / 3750 rpm
Spark plug	NGK: BPR6ES
Spark plug gap	0.7-0.8 mm (0.028-0.031 in)
Spark plug tightening torque	20 N·m (2.0 kg·m, 14 ft·lb)

Valve clearance adjustment data

Calculate the thickness of new adjusting pad so valve clearance comes within specified values.

R = Thickness of removed adjusting pad
N = Thickness of new adjusting pad
M = Measured valve clearance

Intake/Exhaus:
N = R + [M – 0.13 mm (0.005 in)]

Adjusting pads are available from 1.80 mm (0.0708 in) to 3.00 mm (0.1181 in), in steps of 0.05 mm (0.002 in).

Example:
R = 1.80 mm
M = 0.22 mm
N = 1.80 + (0.22 – 0.13) = 1.89 mm, round to 1.90 mm, so we need a adjusting pad with code 190.

Adjust valve celarance at 1000 hr periodic maintenance, normal operational range between periodic maintenance may be 0.02-0.2 mm (0.0008-0.01 in)

Tightening torque
Rocker arm shaft bolt	4.0 Nm (0.40 kg·m, 2.9 lb·ft)
Cylinder head cover bolt	11.0 N·m (1.1 kg·m, 8.0 lb·ft)