________________________________________________________________________________

Yamaha MA190 Engine

General Technical Data

Yamaha MA190 Engine Specifications

Engine Model ................ Yamaha MA190
Engine Type ................ 4-cycle hemi-head OHC 1-cylinder air-cooled gasoline engine
Number of Cylinders ................ Single
Displacement, cu.in (cc) ................ 11.5 (189)
Cylinder Bore, in (mm) ................ 2.67 (68.0)
Piston Stroke, in (mm) ................ 2.05 (52.0)
Rated Engine Power, hp (kW) ................ 5.0 (3.7)
Rated Engine Speed, rpm ................ 3600
Maximum Torque, Nm (ft-lbs) ................ 11.2 (8.3)
Torque Speed, rpm ................ 2400
Compression Ratio ................ 8.5:1
Valve Arrangement ................ Overhead cam
PTO Shaft Rotation ................ Counterclockwise (from PTO shaft side)
Lubrication System ................ Forced splash type
Cooling System ................ Forced air
Air Cleaner Type ................ Clip-on, dry element
Ignition System ................ TCI (transistor controlled ignition)
Starting System ................ Recoil

Fuel System

Fuel System Type ................ Carburetor
Carburetor Type ................ Float
Governor Type ................ Mechanical
Fuel Tank Capacity, qts (L) ................ 1.3 (1.2)
Fuel Type ................ Gasoline (86 or higher)

Dimensions and Weight

Overall Length, in (mm) ................ 16.7 (424)
Overall Width, in (mm) ................ 13.8 (351)
Overall Height, in (mm) ................ 11.7 (297)
Dry Weight, lbs (kg) ................ 30.8 (14.0)

Yamaha MA190 Maintenance Data

Service Data

Cylinder Compression, psi (bar) ................ 167 (11.5)
Cylinder Bore Inside Diameter (Max), in (mm) ................ 2.6830 (68.150)
Cylinder Head (Max. Out of Flatness), in (mm) ................ 0.003 (0.08)
Intake Valve Clearance, in (mm) ................ 0.004-0.006 (0.10-0.15)
Exhaust Valve Clearance, in (mm) ................ 0.006-0.008 (0.15-0.20)

Engine Oil and Filter

Engine Oil Type ................ Yamalube, SAE 10, SAE 10W-30
API Service Classifications ................ SE or SF
Oil Capacity, qts (L) ................ 0.63 (0.60)
Air Filter Element Part Number ................ 7JE-E4451-00

Ignition System

Spark Plug Type ................ Torch E7RTC or NGK BPR7HS
Spark Plug Gap, in (mm) ................ 0.028-0.032 (0.70-0.80)
Coil Air Gap, in (mm) ................ 0.016-0.024 (0.40-0.60)
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 50 hours
Change Engine Oil ................ Every 50 hours
Replace Air Filter Element ................ Every 100 hours
Replace Spark Plug ................ Every 100 hours
Check Fuel Hose ................ Every 100 hours
Clean Fuel Strainer ................ Every 100 hours
Check Carburetor Adjustment ................ Every 100 hours
Check and Adjust Idle Speed ................ Every 100 hours
Check and Adjust Valve Clearance ................ Every 100 hours
Clean Cylinder Head ................ Every 100 hours
Replace Fuel Hose ................ Every 200 hours

Yamaha MA190 Service Specifications

Cylinder Block

Cylinder Block Sleeve Inside Diameter, in (mm) ................ 2.6772-2.678 (68.00-68.02)
Piston Skirt Outside Diameter, in (mm) ................ 2.6767-2.676 (67.989-67.971)
Piston To Cylinder Clearance, in (mm) ................ 0.0004-0.0019 (0.011-0.049)
Piston Pin Bore Inside Diameter, in (mm) ................ 0.6301-0.6303 (16.004-16.01)
Piston Pin Outside Diameter, in (mm) ................ 0.6297-0.6299 (15.994-16.00)
Piston Pin To Piston Pin Bore Clearance, in (mm) ................ 0.0002-0.0006 (0.004-0.016)
Piston Ring Side Clearance (First), in (mm) ................ 0.0016-0.0031 (0.04-0.08)
Piston Ring Side Clearance (Second), in (mm) ................ 0.0016-0.0031 (0.04-0.08)
Piston Ring Width (First), in (mm) ................ 0.0984-0.1063 (2.5-2.7)
Piston Ring Width (Second), in (mm) ................ 0.1024-0.1102 (2.6-2.8)
Piston Ring End Gap (First), in (mm) ................ 0.0051-0.011 (0.13-0.28)
Piston Ring End Gap (Second), in (mm) ................ 0.0079-0.0157 (0.20-0.40)
Connecting Rod Big End Inside Diameter, in (mm) ................ 1.1811-1.1818 (30.000-30.018)
Connecting Rod Small End Inside Diameter, in (mm) ................ 0.6301-0.6307 (16.005-16.021)
Connecting Rod Big Oil Clearance, in (mm) ................ 0.0007-0.0019 (0.019-0.049)
Connecting Rod Big End Side Clearance, in (mm) ................ 0.0157-0.0276 (0.4-0.7)
Crankshaft Pin Outside Diameter, in (mm) ................ 1.1799-1.1804 (29.969-29.981)

Cylinder Head And Valves

Cylinder Head Warpage, in (mm) ................ 0.002 (0.05)
Intake Valve Stem Outside Diameter, in (mm) ................ 0.2142-0.2148 (5.440-5.455)
Exhaust Valve Stem Outside Diameter, in (mm) ................ 0.2138-0.2144 (5.430-5.445)
Intake Valve Guide Inside Diameter, in (mm) ................ 0.2165-0.2173 (5.500-5.520)
Exhaust Valve Guide Inside Diameter, in (mm) ................ 0.2165-0.2173 (5.500-5.520)
Intake Valve Stem Clearance, in (mm) ................ 0.0018-0.0031 (0.045-0.080)
Exhaust Valve Stem Clearance, in (mm) ................ 0.0022-0.0035 (0.055-0.090)
Valve Seat Width, in (mm) ................ 0.0335 (0.85)
Valve Spring Free Length, in (mm) ................ 1.2008 (30.50)
Cam Height (Intake), in (mm) ................ 0.9441 (23.98)
Cam Height (Exhaust), in (mm) ................ 1.0976 (27.88)
Camshaft Spindle Outside Diameter, in (mm) ................ 0.3528-0.3535 (8.96-8.98)

Tightening Torques

Cylinder Head (M8x65), Nm (ft-lb) ................ 24-28 (18-21)
Crankcase Cover (M6x30), Nm (ft-lb) ................ 8-12 (6-9)
Oil Drain Plug (M10x15), Nm (ft-lb) ................ 20-24 (15-21)
Connecting Rod (M6x35), Nm (ft-lb) ................ 12-14 (9-10.5)
Governor Gear (M6x16), Nm (ft-lb) ................ 8-12 (6-9)
Flywheel Nut (M14x1.5), Nm (ft-lb) ................ 60-68 (45-50)
Cylinder Head Cover (M6x80), Nm (ft-lb) ................ 6-10 (4.5-7.5)
Ignition Coil (M6x68), Nm (ft-lb) ................ 8-12 (6-9)