How to troubleshoot & repair any small gas engine PDF
Preview How to troubleshoot & repair any small gas engine
1967 HOW TO TROUBLESHOOT & ,. , REPAIR ANY SMALL PAUL DEMPSEY ' HOW TO TROUBLESHOOT & REPAIR ANY SMALL PAUL DEMPSEY TAB TAB BOOKS Inc . ....___,. Blue Ridge Summit, PA 17214 FIRST EDITION FIRST PRINTING Copyright © 1985 by TAB BOOKS Inc. Printed in the United States of America Reproduction or publication of the content in any manner, without express permission of the publisher, is prohibited. No liability is assumed with respect to the use of the information herein. library of Congress Cataloging in Publication Data Dempsey, Paul How to troubleshoot and repair any small gas engine. Includes index. 1. Internal combustion engines, Spark ignition Maintenance and repair. I. Title. T J790.D44 1985 621.43'4 85-14748 ISBN 0-8306-0967-9 ISBN 0-8306-1967-4 (pbk.) Contents Introduction vii 1 Engine Basics 1 Nomenclature-Operation-Dimensions and Measure ments-Heat Lubrication-Maintenance 2 Ignition 23 Timing-Simple Alignment-Point Gap Adjustment-Point To-Cam Adjustment-Insufficient Output-Conventional Systems-Solid-State Systems 3 Carburetors and Fuel Systems 67 Operation-Types- Adjustments-Filters-Governors Fuel Pumps-Mechanical Pumps 4 Rewind Starters 117 Side Pull-Service Procedures-Briggs & Stratton- Vertical Pull 5 Electrical System 155 Starting Circuits-Charging Systems 6 Engine Mechanics 188 Diagnosis-Scope of Work-Cylinder Head-Valves Pistons and Rings-Cylinder Bores-Connecting Rods Assembly Crankshafts-Camshafts-Main Bearings Seals- Governor Mechanisms-Oiling Systems Index 259 Introduction This book is written for the millions of owners of small engines who want to be able to make their own repairs, and for mechanics who are just getting into small-engine work. It combines some engineering theory with detailed descriptions of repair procedures, including troubleshooting and major engine work. Emphasis is on four-cycle and two-cycle, American-made utility and industrial engines. Briggs & Stratton, Kohler, Onan, Tecumseh and Clinton receive special attention, but techniques described here apply to most makes and models. Major systems are discussed in detail; there are chapters on ignition, carburetion, rewind starters, electrical systems, and engine internals. In each case, some attention has been given to theory, but one cannot repair a carburetor, a magneto, or a rewind starter without understanding how it works. In retrospect, I think that these short descriptions are the most important parts of this book. Readers will remember this type of information and be able to ap ply it for years to come and on engines not yet built. Most small-engine repairs are fairly simple and can be accom plished with no more than the usual collection of kitchen-drawer tools supplimented by a 3/8-inch, square-drive socket set in U.S. or metric sizes. Nevertheless, there are times when factory tools are needed. These tools might not be readily obtainable. To simplify matters, I have included part numbers and, whenever possible, alternate sources of supply or instructions for home fabrication. VII ' Chapter 1 I \ Engine Basics This chapter covers elemental matters about the theory of engine operation, and routine maintenance procedures. Because readers might have little familiarity with the subject, I will begin with what the Army used to call "naming of the parts." Figure 1-1 illustrates major external parts of a typical four cycle, single-cylinder, side-valve, horizontal-crankshaft engine. Most of the labeled parts, such as fuel tank, muffler, carburetor, and air cleaner, are engine accessories, bolted to the basic package. Each of these accessories, including some not highlighted in the illustration, are described in various chapters of this book. The engine proper consists of those parts inside the cavity formed by the cylinder head and cylinder block, and that are not visible until disassembly. Figure 1-2 shows the internal parts of a four-cycle engine in exploded view. Note that the basic engine is quite a simple affair; there are fewer than 20 parts and subassemblies. These parts include: • Cylinder head-caps the cylinder bore and mounts the spark plug. Finned for cooling and almost always cast in aluminum. • Piston- a moving plug that reciprocates in the cylinder bore. Area between the top, or crown, of the piston and the inner face of the cylinder head forms the combustion chamber where gasoline and air are explosively combined to drive the piston. • Piston rings-fitted on the piston to prevent gas leakage 1 I\) ..,..FILLER CAP (KEEP VENT OPEN) ~ FUEL TANK (OPTION) I I I I ' TOP MOUNTED 11.--1-1/2 GAL. SHOWN .........-rr FUEL CYLINDER ~ -==-.:::,--=====-"1 SHUT-OFF HEAD - ~.=~~- VALVE " J - COOL ING FINS ORY TYPE SHOULDER • v, AIR CLEANER TYPE DIPSTICK - • - NAMEPLATE }---"/ (, ~. I ~ AIR BREAKER INTAKE POINT COVER ·: SCREEN 9 1~ ~ GASOLINE CARBURETOR OIL N--~ -- - ~- ORA! ~ ~ BLOWER -"--I ,._~ HOUSING STOP BUTTON L-..------_.J \ PAN FUEL PUMP OR COVER Fig. 1-1. External views of a Kohler single-cylinder engine, with major accessories labeled.
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