The Yamaha MX400 is a 402 cc (24.5 cu-in) single-cylinder air-cooled 4-stroke internal combustion general-purpose gasoline engine with horizontal shaft manufactured by Yamaha Motor Co., Ltd.
The Yamaha MX400 engine has a hemispherical combustion chamber with V-valve layout; float type carburetor; centrifugal flyweight governor; mechanical splashing lubrication system; Transistor Controlled Ignition (T.C.I.) and recoil or electrical (option) starter. The starter knob position can be adjusted by each 45°. Microwave harden crankshaft, camshaft and balancer shaft with dual bearing support provide extremely long. The high-tech exhaust valve (Stellite® coated and tufftride® finished) resists very high temperature. To be pushed the crank down directly, the cylinder arranged off from the crankshaft center.
An 85.0 mm (3.35 in) cylinder bore and 71.0 mm (2.79 in) piston stroke give the engine a total of 402 cc of displacement. Compression ratio rating is 8.2:1. The engine produced 12.8 PS (9.4 kW) at 3,600 rpm of maximum horsepower and 10.6 PS (7.8 kW) at 3,600 rpm of continuous rated power. Maximum torque is 28.7 N·m (2.9 kg·m, 21.2 ft·lb) at 2,400 rpm of torque.
4-stroke, Hemi-head OHV, single cylinder
402 cm3 (24.5 cu-in)
12.8 PS (9.4 kW) at 3,600 rpm
Max. torque (crank PTO)
28.7 N·m (2.9 kg·m, 21.2 ft·lb) at 2,400 rpm
Transistor Controlled Ignition (T.C.I.)
Recoil or Electrical (option)
Unleaded gasoline (octane number 86 or higher)
Fuel tank capacity
6.1 L (1.61 US Gal, 1.34 Imp Gal.)
PTO shaft rotation
Counterclockwise (from PTO shaft side)
Dimensions and Weight
Length, mm (in)
Width, mm (in)
Height, mm (in)
Dry weight, kg (lb)
Intake valve clearance
0.10 mm (0.004 in)
Exhaust valve clearance
0.10 mm (0.004 in)
Yamalube 4-stroke or an equivalent (SE or SF)
SAE 10W-30, 10W-40
1.1 L (1.16 US. qt, 0.97 Imp. qt.)
Spark plug gap
0.7-0.8 mm (0.028-0.031 in)
T.C.I. air gap
0.4 ± 0.2 (0.016 ± 0.008)
Spark plug tightening torque
20 N·m (2.0 kg·m, 14 ft·lb)
ATTENTION! Dear visitors, this site is not a trading platform, an official dealer or a spare parts supplier, so we do not have any price lists or spare parts catalogs. We are an information portal and provide the technical specifications of gasoline and diesel engines.
We try to use verified sources and official documentation, however, differences between sources or errors in entering information may occur. We do not provide advice on technical issues related to the engines operation or repair. We do not recommend using provided information for engines repairing engines or spare parts ordering, use only official service manuals and spare-parts catalogs.
Privacy & Cookies Policy
Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. These cookies do not store any personal information.