MTD 478 Series User Manual

Professional Shop Manual
478/483/490 Series Horizontal Shaft Snow Engines
MTD Products Inc - Product Training and Education Department
FORM NUMBER - 769-04951
05/2009
NOTE: These materials are for use by trained technicians who are experienced in the service and repair of outdoor power
equipment of the kind described in this publication, and are not intended for use by untrained or inexperienced individuals.
These materials are intended to provide supplemental information to assist the trained technician. Untrained or inexperi-
enced individuals should seek the assistance of an experienced and trained professional. Read, understand, and follow all
instructions and use common sense when working on power equipment. This includes the contents of the product’s Oper-
ators Manual, supplied with the equipment. No liability can be accepted for any inaccuracies or omission in this publication,
although care has been taken to make it as complete and accurate as possible at the time of publication. However, due to
the variety of outdoor power equipment and continuing product changes that occur over time, updates will be made to these
instructions from time to time. Therefore, it may be necessary to obtain the latest materials before servicing or repairing a
product. The company reserves the right to make changes at any time to this publication without prior notice and without
incurring an obligation to make such changes to previously published versions. Instructions, photographs and illustrations
used in this publication are for reference use only and may not depict actual model and component parts.
© Copyright 2009 MTD Products Inc. All Rights Reserved

MTD 478 Series Specifications

General

Brand	MTD
Model	478 Series
Category	Engine
Language	English

Summary

MTD Professional Shop Manual

478/483/490 Series Snow Engine Manual

Manual details specific to MTD's 478/483/490 series horizontal shaft snow engines.

CHAPTER 1: INTRODUCTION

Manual Purpose and Conventions

Explains the purpose, audience, and text conventions of the manual.

Fasteners and Assembly Basics

Covers fastener types and general assembly principles.

Engine Model and Serial Number ID

Information on identifying MTD engine models and serial numbers.

Essential Engine Maintenance Procedures

Covers oil changes, spark plug care, valve lash, and cleaning.

Torque Specs and Maintenance Schedule

Reference for torque values and a schedule for required maintenance tasks.

Frequently Used Engine Specifications

Reference table for common engine specifications like valve lash and oil capacity.

CHAPTER 2: BASIC TROUBLESHOOTING

Troubleshooting Definitions and Steps

Defines terms and outlines the systematic process for diagnosing engine problems.

Problem Identification and Cause Analysis

Steps for defining the problem and identifying potential causes.

Diagnostic Tests and Repair Guidance

Covers prime test, leak-down, compression, PCV tests, and repair principles.

CHAPTER 3: AIR INTAKE SYSTEM

Heat Box and Carburetor Service

Details on the heat box's role and instructions for carburetor/insulator service.

Carburetor and Insulator Removal

Instructions for removing and servicing the carburetor and insulator assembly.

CHAPTER 4: THE FUEL SYSTEM AND GOVERNOR

Fuel System Inspection and Testing

Covers fuel inspection, alcohol testing, vent/filter service.

Fuel Lines, Tank, Choke, and Primer Service

Procedures for fuel lines, tank, choke, and primer systems.

Carburetor Service and Rebuilding

Detailed steps for inspecting, cleaning, and rebuilding the carburetor.

Governor System Operation and Adjustment

Explanation of the governor's function and how to adjust engine speed.

CHAPTER 5: LUBRICATION

Oil Specifications and Level Checking

Recommended oil type, capacity, and procedure for checking the level.

Lubrication System Components and PCV Valve

Details on dipstick tube, lubrication system, and PCV valve.

CHAPTER 6: STARTER AND CHARGING SYSTEMS

Recoil Starter Assembly Service

Procedures for removing, servicing, and replacing recoil starter components.

Electric Starter and Charging System

Details on electric starter replacement and charging system testing.

CHAPTER 7: IGNITION SYSTEM

Ignition System Troubleshooting Steps

General steps for diagnosing ignition system issues.

Stop Switch and Ignition Testing

Procedure for testing the stop switch and remote ignition switch.

Ignition Module, Flywheel, and Spark Plug Service

Service for ignition module, flywheel, and spark plugs.

Spark Plug Removal and Installation

Steps for removing and installing the spark plug, including torque specs.

CHAPTER 8: EXHAUST

Muffler Removal and Replacement

Procedure for removing and replacing the engine muffler.

CHAPTER 9: CYLINDER HEAD

Cylinder Head Removal and Installation

Step-by-step instructions for removing and installing the cylinder head.

Valve Service Procedures

Instructions for servicing engine valves, including removal and inspection.

CHAPTER 10: CRANKSHAFT, PISTON AND CONNECTING ROD

Component Inspection (Crankshaft, Piston, Rod)

Methods for inspecting crankshaft, pistons, rings, connecting rods, and cylinders.

Balance Shaft and Engine Reassembly

Details on balance shaft function and comprehensive engine reassembly steps.

Engine Specifications and Torque Charts

Reference tables for engine dimensions, tolerances, and fastener torque values.

CHAPTER 11: FAILURE ANALYSIS

Abrasive Ingestion and Lubrication Failures

Analysis of engine damage from abrasive particles and insufficient lubrication.

Overspeed, Overheating, and Mechanical Failures

Analysis of engine damage from overspeed, overheating, mechanical breakage, and wear.

Detonation and Preignition Analysis

Explanation of detonation/preignition causes and associated engine damage.