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Yamaha MZ175 Engine

General Technical Data

Yamaha MZ175 Engine Specifications

Engine Model ................ Yamaha MZ175
Engine Type ................ 4-cycle overhead valve 1-cylinder air-cooled small gasoline engine
Number of Cylinders ................ Single
Displacement, cu.in (cc) ................ 10.4 (171)
Cylinder Bore, in (mm) ................ 2.60 (66.0)
Piston Stroke, in (mm) ................ 1.97 (50.0)
Rated Engine Power, hp (kW) ................ 4.8 (3.5)
Rated Engine Speed, rpm ................ 3600
Maximum Torque, Nm (ft-lbs) ................ 10.5 (7.7)
Torque Speed, rpm ................ 2400
Compression Ratio ................ 8.5:1
Cylinder Liner ................ Cast iron
Valve Arrangement ................ OHV
PTO Shaft Rotation ................ Counterclockwise (from PTO shaft side)
Lubrication System ................ Forced splash type
Cooling System ................ Forced air
Air Cleaner Type ................ Semi-dry, dual, or semicyclone
Ignition System ................ TCI (transistor controlled ignition)
Starting System ................ Recoil or electric starter

Fuel System

Fuel System Type ................ Carburetor
Carburetor Type ................ Float
Governor Type ................ Centrifugal, flyweight
Fuel Tank Capacity, qts (L) ................ 4.8 (4.5)
Fuel Type ................ Gasoline (86 or higher)
Fuel Consumption, g/ps-h ................ 210

Dimensions and Weight

Overall Length, in (mm) ................ 12.8 (325)
Overall Width, in (mm) ................ 14.2 (361)
Overall Height, in (mm) ................ 14.6 (370)
Dry Weight, lbs (kg) ................ 26.7 (17.0)

Yamaha MZ175 Maintenance Data

Service Data

Cylinder Bore Inside Diameter (Max), in (mm) ................ 2.6043 (66.150)
Cylinder Head (Max. Out of Flatness), in (mm) ................ 0.003 (0.08)
Intake Valve Clearance, in (mm) ................ 0.004 (0.10)
Exhaust Valve Clearance, in (mm) ................ 0.002-0.004 (0.05-0.10)

Engine Oil and Filter

Engine Oil Type ................ Yamalube, SAE 10W, SAE 10W-30, 10W-40
API Service Classifications ................ SE or SF
Oil Capacity, qts (L) ................ 0.63 (0.60)
Air Filter Element Part Number ................ 7CN-E4451-00

Ignition System

Spark Plug Type ................ NGK BPR4ES
Spark Plug Gap, in (mm) ................ 0.028-0.032 (0.70-0.80)
Coil Air Gap, in (mm) ................ 0.02 (0.50)
Ignition Timing, degrees ................ 23 BTDC
Spark Plug Torque, Nm (ft-lbs) ................ 18 (13)

Carburetor Adjustment

Carb Model ................ Mikuni BV-20-15
Main Jet ................ #81.3
Pilot Jet ................ #78.8
Float Height, in (mm) ................ 0.63 (16.0)
Pilot Screw Opening ................ 2-1/8 turns out
Low Idle Speed, rpm ................ 2000±100
High Idle Speed, rpm ................ 3800±50

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 100 hours
Clean Fuel Filter ................ Every 100 hours
Clean Fuel Strainer ................ Every 100 hours
Check Fuel Hose ................ Every 100 hours
Replace Spark Plug ................ Every 200 hours
Replace Air Filter Element ................ Every 200 hours
Check Carburetor Adjustment ................ Every 200 hours
Check Breather Hose ................ Every 300 hours
Check and Adjust Idle Speed ................ Every 300 hours
Check and Adjust Valve Clearance ................ Every 300 hours

Yamaha MZ175 Service Specifications

Cylinder Head And Valves

Cylinder Head Flatness, in (mm) ................ 0.04 (0.10)
Valve Head Diameter (Intake), in (mm) ................ 0.94 (24.0)
Valve Head Diameter (Exhaust), in (mm) ................ 0.87 (22.0)
Valve Stem Lenght (Intake), in (mm) ................ 2.59 (65.9)
Valve Stem Length (Exhaust), in (mm) ................ 2.54 (64.5)
Valve Seat Width, in (mm) ................ 0.003 (0.70)
Valve Guide Inside Diameter, in (mm) ................ 0.22 (5.50)
Valve Stem To Valve Guide Clearance (Intake), in (mm) ................ 0.0016-0.002 (0.04-0.06)
Valve Stem To Valve Guide Clearance (Exhaust), in (mm) ................ 0.002-0.003 (0.06-0.08)
Valve Spring Free Length, in (mm) ................ 1.04 (26.5)

Cylinder Block

Cylinder Inside Diameter, in (mm) ................ 2.5986-2.5990 (66.005-66.015)
Piston Skirt Diameter, in (mm) ................ 2.598 (66.0)
Piston Ring Groove Side Clearance (Top), in (mm) ................ 0.0016-0.003 (0.04-0.08)
Piston Ring Groove Side Clearance (2nd), in (mm) ................ 0.008-0.0024 (0.02-0.06)
Piston Pin Outside Diameter, in (mm) ................ 0.6297-0.6299 (15.995-16.000)
Clearance Between Piston And Cylinder, in (mm) ................ 0.00059-0.00157 (0.015-0.040)
Piston Ring End Gap (Top), in (mm) ................ 0.008-0.016 (0.2-0.4)
Piston Ring End Gap (2nd), in (mm) ................ 0.008-0.016 (0.2-0.4)
Piston Ring End Gap (Oil), in (mm) ................ 0.008-0.016 (0.2-0.4)
Connecting Rod Big End Inside Diameter, in (mm) ................ 1.1023-1.1029 (28.000-28.015)
Connecting Rod Small End Inside Diameter, in (mm) ................ 0.6301-0.6307 (16.006-16.020)
Crankpin Outside Diameter, in (mm) ................ 1.10 (28.0)
Crankshaft Big End Side Clearance, in (mm) ................ 0.008-0.024 (0.2-0.6)
Cam Height (Intake), in (mm) ................ 1.06 (26.9)
Cam Height (Exhaust), in (mm) ................ 1.05 (26.68)
Camshaft Journal Outside Diameter, in (mm) ................ 0.5895-0.5901 (14.193-14.989)

Tightening Torques

Cylinder Head (M8x1.25), Nm (ft-lb) ................ 20 (14.5)
Cylinder Head Cover (M6x1.0), Nm (ft-lb) ................ 10 (7.2)
Connecting Rod Cap (M7x1.0), Nm (ft-lb) ................ 12 (8.7)
Flywheel Magneto (M14x1.5), Nm (ft-lb) ................ 65 (47)
Governor Arm (M6x1.0), Nm (ft-lb) ................ 8 (5.8)
Crankcase Cover (M8x1.25), Nm (ft-lb) ................ 22 (15.9)
TCI unit (M6x1.0), Nm (ft-lb) ................ 10 (7.2)
Valve Adjuster Locknut (M6x0.5), Nm (ft-lb) ................ 10 (7.2)
Oil Drain Plug (M10x1.25), Nm (ft-lb) ................ 17 (12)