The Yamaha MZ250 is a 253 cc (15.4 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 MZ250 engine has an OHV (overhead valve) design; float type carburetor; centrifugal flyweight governor; mechanical splashing lubrication system; Transistor Controlled Ignition (T.C.I.) and recoil or electrical (option) starter. The Yamaha MZ250 used aluminum cylinder block with a spiny cast-iron sleeve. For exhaust valve used high heat resistant SUH3 steel.
The cylinder bore is 74.0 mm (2.91 in) and the piston stroke is 59.0 mm (2.32 in), compression ratio rating is 8.7:1. The engine produced 7.3 PS (5.4 kW) at 3,600 rpm of maximum horsepower and 6.1 PS (4.5 kW) at 3,600 rpm of continuous rated power. Maximum torque is 15.7 N·m (1.60 kg·m, 11.6 ft·lb) at 2,400 rpm.
4-stroke, OHV, single cylinder
253 cm 3 (15.4 cu-in)
7.3 PS (5.4 kW) at 3,600 rpm
Max. torque (crank PTO)
15.7 N·m (1.60 kg·m, 11.6 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
5.5 L (1.45 US Gal, 1.21 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
1.0 L (1.06 US. qt, 0.88 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)
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