Small Engine Repair - Grade10BBT - homegrade10bbt.wikispaces.com/file/view/Small+engine+repair...Small Engine Repair 2 Version 1.0 3/19/10 Overview Research Two & Four Stroke Engines

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Small Engine Repair

ACTIVITY GUIDE

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Overview

Research Two & Four Stroke Engines

Activity 1 – Disassemble Engine

Activity 2 – Assemble Engine

Objectives

In this module the student will:

Identify the theory, uses and operation of small gas engines.

Explore engine operation using the four-stroke and two-stroke cycle principles.

Develop knowledge of proper and safe tool usage.

Interact with the mechanical, electrical and fuel systems of a small gas engine.

Complete the disassembly and reassembly of a small gas engine.

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Required Items

All of the required tools and equipment you will need to complete this module are available from your teacher

Socket Set

Basic Socket Set consisting of both Metric and Standard sizes

Wrenches

A set of small wrenches containing both Metric and Standard sizes

Hammer There are two different types of hammers for this project (you only need a soft hammer).

The top one is a plastic hammer. It is used for gently tapping a part to help it move.

The bottom one is a brass hammer. It is heavier and can break some parts of the engine. BE SURE OF WHAT YOU ARE ABOUT TO STRIKE WHEN USING THIS HAMMER!

You will also required some specialized tools which can be obtained from your

teacher when you need them.

Flywheel holder This tool holds the flywheel stationery while you loosen the nut that holds it to the engine.

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Clutch tool This is used to remove the one-way starter clutch (the ripcord)

0 - 3” micrometers This tool is used to measure the

cylinder bore very precisely

(accurate to 0.001 of an inch)

Feeler Gauges - Up to 0.35

These are for measuring the gap

in the spark plug and distance

between the magneto and the

flywheel.

Compression Tester An engine won’t run (or it will

produce blue smoke) if there

are leaks in the engine.

Valve spring compressor

This is an important tool for

inserting and removing the

valves.

Flywheel Puller This tool is used to pull the

flywheel free of the crankshaft

without damaging either.

Piston Ring Compressor This tool compresses the rings so the

piston can be re-inserted into the

cylinder.

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Small Gasoline Engines

Topic 1: Introduction

Read through the information to learn about small gas engines. An assignment follows to test your knowledge from the readings.

A gasoline-fueled engine is an internal combustion engine designed to transform the chemical energy of burning fuel (gasoline that is combined with air) into mechanical energy that can mow lawns, cut trees, power generators and various other things. You will learn in the pages that follow that there are four strokes that the piston must make to complete a cycle: Intake, Compression, Power and Exhaust.

There are five basic systems that make up a small gas engine that we will look at during this module:

1. Mechanical – the design and construction of the engine

2. Carburetion – the mixing of the air with the gas and admitting it to the cylinder

3. Ignition – firing of the fuel charge in the combustion chamber

4. Cooling – a method of removing the heat from the engine

5. Lubrication – the ability to get the oil to all of the moving parts

Mechanical

Take out the engine to identify each part as you are reading the information below. The important parts of any internal combustion engine are:

Cylinder Block – the cylinder block is usually cast from either iron or aluminum alloy. The cylinder block is what keeps all of the engine parts in alignment. The cylinder itself can either be bored directly into the cast iron or sometimes a steel sleeve will be inserted into an oversized hole (that is the case in the aluminum cylinders). Aluminum is a soft metal and the movements of the piston would wear out the cylinder walls very quickly without the steel sleeve. Aluminum is used because of the ability to dissipate (move away) heat quickly and it is very lightweight. The fins, called cooling fins that you see around the outside of the cylinder block direct the air around the engine to help keep it cool.

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Cylinder – This is the large hole in the center of the engine where the piston travels up and down. You can only see this when the engine is disassembled (remove the cylinder head). The gasoline-air mixture enters and exits the cylinder through the ports or valves in the cylinder. The ported cylinder can also be referred to as the combustion chamber. When combustion takes place, all ports or valves must be closed.

Crankcase – the crankcase is designed to be rigid and strong to withstand the rotational forces (spinning) of the crankshaft as well as to protect the internal parts of the engine. In four-stroke engines, oil for the lubrication of the engine is contained in the crankcase, in two-stroke engines oil and gas are passed through the crankcase before entering the combustion chamber. Oil and gasket seals are used to keep out dirt and keep the oil clean.

Piston – the piston is what transfers the energy of the combustion into the output energy of the crankshaft. The piston is exposed to the extreme heat of the combustion and will expand in diameter, therefore, it is slightly smaller than the inside diameter of the cylinder. There are rings around the outside of the piston that make contact with the cylinder. The piston rings provide a seal between the combustion chamber and the crankcase keeping the exhaust gases above the piston and not allowing the lubricating oil to leak into the combustion chamber. The cylinder walls are lubricated with oil from the crankcase and allow the piston to move freely within the cylinder.

Connecting rod – The piston is connected to the crankshaft by the connecting rod. The connecting rod is connected on one end to the piston and on the other to a journal (that is offset) on the crankshaft. By being offset, the motion of the piston allows the crankshaft to be rotated in a circular direction.

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Crankshaft – the crankshaft is made from either cast steel or forged steel and it is the major rotating part of the engine. The surfaces of the crankshaft are precisely machined and ground to specific dimensions. The crankpin or connecting rod journal is offset from the center of the crankshaft to allow the piston to move up and down in the cylinder. This offset is called the throw of the crankshaft. Counterweights are used on the opposite side of the crankshaft as the offset to balance the weight of the connecting rod. The tapered end of the crankshaft always fits into the flywheel that has a tapered hole that matches. Together this taper provides very good holding power. The crankshaft is held in an exact position within the cylinder block by roller bearings. Roller bearings are used with highly polished bearing races that are pressed into the crankcase. Together, the roller bearing and the bearing race provide very little friction and a very good resistance to wear.

A key (piece of square metal) is also used to make sure the flywheel is placed in the correct position on the crankshaft. This is so the magnets in the flywheel approach the ignition coil at the exact same time as the piston approaches top dead center in the cylinder.

Assignment 1: Answer all questions on your own paper. Label it Assignment1

1. What two materials are used to make the cylinder block?

2. Why is a steel sleeve sometimes used in an aluminum cylinder block?

3. Why is aluminum used for cylinder heads (2 reasons)?

4. What do the cooling fins do for an engine?

5. What is the hole called that holds the piston while it travels up and down?

6. Why does the crankcase have to built strong?

7. What is used for lubricating the parts in the crankcase of a four-stroke engine?

8. What is used for lubricating the parts in the crankcase of a two-stroke engine?

9. Why is the piston a little smaller than the cylinder hole?

10. How is the piston lubricated so that it flows freely up and down?

11. Why are there expandable rings on the piston?

12. What is the function of the connecting rod?

13. Name the major rotating part in the cylinder block.

14. What is the benefit of using bearing on each end of the fast turning crankshaft?

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Topic 2:

Two-Cycle Engine

Two Cycle and Four Cycle Engines When speaking of engines, they can be referred to as two cycle or two stroke, four cycle or four stroke. Both terms (cycle and stroke) refer to the same thing. The stroke is the movement of the piston from BDC (bottom dead center) to TDC (top dead center) or from TDC (top dead center) to BDC (bottom dead center) depending on the direction that the piston is moving in the cylinder.

In a two-cycle engine, the piston completes the intake and compression stages in the single stroke. On the second stroke of the two-cycle engine, the power and exhaust

stages are completed. This is all accomplished in one 360 rotation of the crankshaft. This allows for the two-cycle engine to accelerate much faster than the four-cycle engine.

A lot of things are happening simultaneously in the two-cycle engine. Visit the following website for further explanations and animations:

http://science.howstuffworks.com/two-stroke.htm

Photo Source: Two-cycle Engine Applications and Lubrication Needs, MS Oil Corporate Web Site, Internet, Oct 10, 2003, www.amsoil.com/articlespr/ article_2cycleapplications.htm

Photo Source: Two-cycle Engine Applications and Lubrication Needs, MS Oil Corporate Web Site, Internet, Oct 10, 2003, www.amsoil.com/articlespr/ article_2cycleapplications.htm

Photo Source: Two-cycle Engine Applications and Lubrication Needs, MS Oil Corporate Web Site, Internet, Oct 10, 2003, www.amsoil.com/articlespr/ article_2cycleapplications.htm

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Assignment 2: Click on the link “two stroke basics” (top right of the page). Look at the diagram and the explanation.

1. List the three advantages of a two-stroke engine over a four-stroke engine.

Now, click on “How Horsepower Works” in the yellow box, part way down the page. Now, find the “Definition” link.

2. Who invented the term horsepower?

3. What else was this guy famous for (2 things)?

4. Explain the meaning of the word horsepower as it relates to the amount of work done.

5. Find the amount of horsepower for the engine that you are working on. Now, click on Measuring Horsepower.

6. What kind of instrument is used to measure horsepower?

7. What does this instrument do?

From the information written in this section of the module book, answer this question.

8. What is the problem if the gasket that seals the parts together gets a tear in it?

9. What is the difference between a two-stroke engine and a two-cycle engine?

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How a two-cycle engine works: Take a look at the diagram of the two-cycle engine from the web site as you read how a two-cycle engine works.

As the piston moves from BDC (bottom dead center) toward TDC (top dead center), a low-pressure area is created in the crankcase, which causes the air/fuel (oil) mixture to be drawn into the crankcase. At the same time, the air/fuel (oil) mixture above the piston is being compressed into the combustion chamber.

Just before the piston reaches TDC (top dead center), the spark plug ignites the air/fuel (oil) mixture, forcing the piston down. This creates a high-pressure area in the crankcase. This high-pressure stops any more air/fuel (oil) mixture from entering the crankcase.

As the burning gases expand, power is transferred from the piston to the crankshaft.

As the piston moves down in the cylinder, the exhaust port is the first to open. This allows the burning air/fuel (oil) mixture to escape into the exhaust system.

A little further down the cylinder, the intake port opens. This allows the pressurized air/fuel (oil) mixture in the crankcase to force into the cylinder, which pushes any remaining burnt fuel out into the exhaust system.

The piston then starts to move back up the cylinder from BDC (bottom dead center) starting the process all over again.

Because of the importance of air pressures in a two-stroke engine, it is essential that all seals and gaskets do their job. If there were a leak in one of the seals or gaskets in the crankcase of a two-stroke engine, the engine would draw air through the seal and into the combustion chamber instead of drawing the air fuel mixture.

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Topic 3:

Four-Cycle Engine

In a four-cycle engine, each stage has its own stroke of the piston. As the piston moves from TDC (top dead center), to BDC (bottom dead center) the intake stroke occurs. As the piston moves from BDC (bottom dead center) to TDC (top dead center) the compression stroke occurs. As the piston then moves again from TDC (top dead center), to BDC (bottom dead center) the power stroke occurs, and finally as the piston moves from BDC (bottom dead center) to TDC (top dead center), the exhaust stroke occurs. Then the process

starts all over again. It takes 720 or two full rotations of the crankshaft for everything to happen in the four-cycle engine.

Both the two and four-cycle engines complete four distinct events in order to operate:

1. Air/fuel mixture is brought into the combustion chamber during the intake stroke. 2. The air/fuel mixture is squeezed during the compression stroke. 3. The spark plug ignites the air/fuel mixture, forcing the piston down during the power

stroke. 4. The burnt air/fuel mixture is forced from the combustion chamber during the exhaust

stroke.

Intake Stroke

Piston moving down creates a vacuum in the cylinder drawing in the air/fuel mixture

The intake valve is open

The exhaust valve is closed

Compression Stroke

Piston moving up compresses the air/fuel mixture

The intake and exhaust valves are both closed

Power Stroke

Air/Fuel mixture ignited by spark plug

Piston moves down

Intake valve closed

Exhaust valve closed

Exhaust Stroke

Piston moves up

Gases forced out

Intake valve closed

Exhaust valve open

Photo Source: Two-cycle Engine Applications and Lubrication Needs, MS Oil Corporate Web Site, Internet, Oct 10, 2003, www.amsoil.com/articlespr/ article_2cycleapplications.htm

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Four Stroke Instructions: “Stroke” Column: Write the name of each stroke in the proper order. The intake stroke has been done for you. “Piston Movement” Column: Write the direction that the piston is moving (up or down) during the stroke listed in the stroke column. “Intake Valve Position” Write the intake valve position (open or closed) during the stroke listed in the stroke column for the four-stroke and the intake port situation for the two-stroke engine. “Exhaust Valve Position” Write the exhaust valve position (open or closed) during the stroke listed in the stroke column.

Assignment 3: Use the textbook as a resource to fill in the blanks on the Four Stroke Cycle Chart. This chart indicates which way the piston & valves are moving during each stroke or cycle. You will get the answers from the information above or use a small gas engine textbook as an additional resource. Do not write in this book – recreate the chart on your own paper.

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Four-Stroke Cycle Chart

Stroke

Piston

Movement

Intake Valve

Position

Exhaust

Valve Position

Intake

Two Stroke Instructions: “Stroke” Column: Write the name of each stroke in the proper order. “Piston Movement” Column: Write the direction that the piston is moving (up or down) during the stroke listed in the stroke column. “Intake Port Situation” Column: Describe what is taking place with the intake port (up or down) during the stroke listed in the stroke column. “Exhaust Port Situation” Column: Describe what is taking place with the exhaust port (up or down) during the stroke listed in the stroke column.

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Two-Stroke Cycle Chart

Stroke Piston

Movement

Intake Port

Situation

Exhaust Port

Situation

Intake/Compression

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Topic 4: Carburetion

Gasoline engines cannot run on liquid gasoline alone. The liquid gasoline must be mixed with air in the proper proportions for an engine to run and this is done so in the carburetor. This itself is not a difficult thing to do, however, a simple valve to mix the air and gas is not sufficient to do this. A simple mixing valve cannot provide the smooth engine operation and economical fuel consumption the varying speeds of an engine require. This is the main reason why there are so many designs and styles of carburetors. Carburetors mix the gasoline and air to provide for an engines various operating conditions such as:

Hot or cold starting

Idling

Part throttle

Acceleration

High speed operation

The principle of operation of the carburetor is that air enters the carburetor either though the top, bottom or side (depending on the type of carburetor) and is mixed with liquid fuel. The liquid fuel is fed through passages in the carburetor and sprayed into the air stream. Atmospheric pressure and the vacuum that is created in the cylinder during the intake stroke draw the air/fuel mixture into the combustion chamber.

Atmospheric pressure is the pressure produced by the weight of air molecules above

the earth and this pressure varies with altitude.

Assignment 4

Gasoline

Gasoline is a mixture of hydrogen and carbon (a hydrocarbon fuel) that contains a great amount of energy. Gasoline that is used in engines must:

Be Clean – free of dirt, water and abrasive particles

Be able to ignite readily, burn clean and resist violent explosion (detonation) without an external source of ignition

Gasoline is available in different grades. Some of the more common grades are

regular (low) and premium (high). Some petroleum companies offer a mid-grade option as well. The major difference between these grades is the octane level. The octane level is the gasoline‟s ability to resist detonation. The lower the octane number, the faster the gasoline will burn therefore, regular grade gasoline is used in low compression, small

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engines. Premium gasoline contains a higher level of octane and therefore burns slower. Premium grade gasoline is typically used in high compression engines. Ignition Systems

The ignition system of the small gasoline engine provides the electrical voltage to discharge a spark across the gap of the spark plug to ignite the air/fuel mixture in the combustion chamber. This high voltage as well as the high rate of discharge that is required to produce this spark, is done at a precise degree of timing that is in sync with the stroke of the piston. The spark must fire at exactly the right time in order to ignite the mixture and produce the power for the power stroke. The number of times an ignition system must create the spark across the spark plug gap is very high. In a two-cycle single cylinder engine, operating at 3200 revolutions per minute (RPM), the ignition system will fire 3200 times per minute. A four cycle single cylinder engine operating at 3200 RPM will fire only 1600 times per minute. In engines that have more than one cylinder, the number of times the ignition will create a spark will multiply by the number of cylinders. (For example: a two cylinder four-cycle engine operating at 3600 RPM would fire 3600 times per minute – 1800 times in each cylinder)

Most small gasoline engines use a magneto system to supply the ignition spark. The major benefit of using a magneto system is that it does not require an outside primary source of electricity to produce the electrical spark. Two of the more common magneto systems used on small gas engines are the mechanical breaker ignition (MBI) system and the solid state ignition system. The MBI ignition system uses mechanical breaker points to control current in the ignition coil. A solid state ignition system is any ignition system that uses electronic components to control the current in the ignition coil.

A magneto system is a very reliable and simple ignition system and the basic parts of the system are:

Permanent magnets – mounted on the flywheel creates a magnetic field when passing by the iron core.

High tension coil – operates like a transformer, the coil contains a common laminated iron core with two windings of wire around it that are separated from each other by insulation. The wire that is closest to the laminated iron core is the primary winding and is wound of a heavy gauge wire. The primary winding is connected on one end to the laminated stack and depending on the type of ignition, is connected on the other end to either the breaker point pivoting arm or an electronic component in a solid state ignition. The outer winding is formed of many turns of light gauge wire (not much bigger in diameter than a human hair), the secondary winding is connected on one end to the laminated stack and the spark plug wire on the other. The ratio of primary windings to secondary windings is approximately 1:60. This means that for every turn of the primary winding there is approximately 60 turns of the secondary winding

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– most coils have about 425 meters (1400 feet) of wire in the secondary winding.

Mechanical or Electronic switching device – in a mechanical switching device, breaker points are used to control the current in the ignition coil. Electronic switching devices (transistors, capacitors, diodes) control various switching operations in a solid state ignition system.

Condenser – used only in mechanical switching devices to prevent current from „jumping‟ across the breaker points as they are opening

High tension spark plug wire – transfers the high voltage current from the secondary winding in the coil to the spark plug terminal nut.

Spark plug – the high voltage current that passed through the spark plug wire to the terminal nut travels through the center electrode of the spark plug to the spark plug gap. If there is enough electrical current to jump the gap from the center electrode to the grounded electrode, a spark will occur and ignite the air/fuel mixture.

Mechanical Breaker Point Ignition (MBI) Systems

Mechanical Breaker Point Ignition (MBI) Systems were used on small gas engines until about the mid-eighties and there are still lots of small engines around that have them. Breaker point ignition systems use a mechanical switch to control the timing of the ignition. Breaker points contain a stationary point that is grounded directly to the engine and a pivoting point that is connected to the primary winding. The pivoting breaker point is spring-loaded and is actuated by the point plunger that follows a surface on the crankshaft. The moving parts in this system can present ignition trouble from general fatigue and are susceptible to poor working conditions. Also, the breaker point faces can become pitted and burnt reducing the efficiency of the ignition system, decreasing the output of the engine and increasing pollution.

The principle behind the breaker point ignition system is when the permanent magnets in the outside diameter of the flywheel approach the laminated iron core of the coil assembly; it produces a moving magnetic field that passes through the laminated stack. The position of the magnets on the flywheel is timed with the flat spot machined on the crankshaft. This flat spot allows the breaker point plunger to fall and close the gap between the breaker points. This closes the electrical circuit and creates a low voltage current in the primary windings. This low voltage current creates a magnetic field within the coil. As the crankshaft continues to rotate, the flat spot terminates and pushes the point plunger up to open the points. When the points open, the circuit is opened and the magnetic field created by the low voltage current in the primary winding collapses. The windings in the coil cut the magnetic field as it collapses and this produces a very high voltage in the secondary circuit. This high voltage travels through the spark plug wire and in turn causes a spark to jump across the spark plug gap and ignite the air/fuel mixture in the combustion chamber.

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Capacitive Discharge Ignition (CDI) Systems

A Capacitive Discharge Ignition (CDI) System is a solid state ignition system made

of electronic semi-conductors (diodes, transistors, silicon controlled rectifiers, etc.) in place of the mechanical points and accessories found in a mechanical breaker ignition system. The CDI system is a compact and sealed unit that has no moving parts other than the flywheel magnet therefore there is no need for maintenance. It is standard equipment on most small engine applications today and has greatly improved the reliability of these engines. CDI systems provide many advantages over mechanical breaker point ignition systems:

No breaker points to wear out and need replaced

Increase spark plug life

Easier starting even with flooded engines and fouled plugs

Faster voltage rise and higher spark output

Spark advance is automatic – because it is electronic it never needs adjustment

Delivers uniform performance throughout life – it is either good or bad

Provides smoother power under load and improves idling

The principle of operation behind the solid state Capacitive Discharge Ignition is much the same as that of the mechanical breaker point ignition. As the magnets in the flywheel approach the armature (laminated stacks) there is a small voltage produced within the small coil of copper wire (trigger coil). This small voltage (approximately .65 v) is enough to turn on the transistor pair and closes the circuit to the primary winding. The electrical current passing through the primary circuit creates a magnetic field much the same as in the breaker point ignition.

The trigger coil is polarity sensitive, meaning that the flywheel magnets have to follow a certain polarity for the coil to work. The correct polarity for a CDI system is north south north. If the CDI is exposed to the wrong polarity it will not function correctly therefore it is important to not mix and match parts of a CDI system with that of another system. As the flywheel turns past the point in the trigger coil where optimum electrical generation occurs, the voltage in the trigger coil drops to zero and turns off the transistor pair opening the circuit. The opening of this circuit stops the flow of electricity through the primary winding, collapsing the magnetic field and in turn, generates the high voltage current in the secondary winding. The high voltage current then travels through the spark plug wire to the spark plug that ignites the air/fuel mixture in the combustion chamber.

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Testing the CDI module

A very simple test can be performed to check for proper operation by grounding a spark plug that is known to be good to the engine. Turn the flywheel by pulling the starter cord and watch the spark plug electrode gap for a spark. If there is a spark, the CDI module is operating correctly. If there is no spark seen after pulling the cord two or three times the following troubleshooting suggestions could be the cause: a faulty ignition switch or switch lead, or the air space between the CDI module and the flywheel may be too much or too little. The ignition switch must be kept clean and dry; it is the most vulnerable part of the solid state ignition system. Lubrication

Two-Stroke Engine Lubrication Systems From reading above, you have learned that in a two-stroke engine the fuel that is burnt contains oil. The reason for this is lubrication. Lubrication is the process of reducing friction between sliding surfaces by introducing a slippery or smooth substance between them. Friction is the resistance to motion created when one dry surface rubs against another. Automotive engine oils are not suitable for two-stroke, air-cooled engines because air-cooled engine operation covers a wider range of varying speeds as well as much higher combustion chamber temperatures. Automotive engine oils contain additives that do not burn completely and leave a residue that fouls spark plugs and can clog exhaust ports. Two-stroke engine manufacturers recommend the use of diluted, two-cycle engine oil. There is basically two ways that a two-stroke engine can be lubricated: (1) by pre-mixing the oil with the gas and, (2) through oil injection (commonly used in snowmobiles, personal watercraft, and dirt bikes).

(1) Pre-mixing oil and gas – by pre-mixing the oil and gas together at the specified oil-to-fuel ratio stated by the manufacturer, the two-stroke engine will be supplied with sufficient lubrication. It is very important to know the specified ratio for the particular engine because having to much oil will create a lot of smoke, foul the spark plug, decrease power output and clog exhaust ports. In operation, an oil mist is created that lubricates the cylinder wall and all internal engine parts.

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(2) Oil injection – in oil injection systems the oil is NOT pre-mixed with the gas. The oil is placed in a separate tank (usually in a location higher than the engine) and is then either fed to the carburetor by either gravity or with the assistance of an oil pump. The oil is then mixed with the gas and air in the carburetor and proceeds to lubricate the internal parts of the engine in the same manner as the pre-mixed method. Oil injection systems are not suitable for all two-stroke engine applications such as power chain saws and lawn trimmers as these devices can be operated in many different positions.

Four Stroke Engine Lubrication Systems

The oil that is stored in the crankcase lubricates four stroke engines. Using too much oil or oil of the wrong grade can cause the engine serious damage. There are a number of methods of which four-stroke small engines can be lubricated. The two most common are the splash system or the pump system. The splash system lubricates the engine through the motion of the crankshaft in addition to a splash finger that is connected to the connecting rod cap that dips down into the oil and then deflects it throughout the crankcase. The pump system picks up the oil and circulates it through an oil filter to clean it and circulates some through a spray nozzle pointed at the crankshaft. While the shaft rotates, it deflects oil throughout the crankcase. Engine oil is also pumped through a tube to the governor assembly as well as through the connecting rod to lubricate the bearings and piston pin. Four-stroke engines must be operated in an upright position because oil would drain away from the pump or splash finger-preventing lubrication.

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Activity 1 In this activity you will disassemble the engine

Safety First! Read the following safety guidelines before starting the activities.

General Safety Considerations

Carefully read through all of the instructions so that you have an overview of what you will be doing during the project

Wear proper eye protection AT ALL TIMES WHILE IN THE LAB, as well as ear protection and protective clothing

Secure hair and loose clothing

Work in areas with good lighting

Make sure all other students are at a safe distance before using the tool

Keep tools free of oil, grease, and foreign matter

Use the tool for its designed use

Secure small work in a clamp or vise

Repair or replace damaged tools

Report any and all injuries to the teacher

Review the safety procedures and operating instructions with your teacher for each tool that you will be using.

DO NOT use any tool without letting your teacher know when you are ready to begin

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Hand Tool Safety Considerations

Point cutting tools away from the body during use

Grind excess metals from mushroomed chisels

Organize tools to protect and conceal sharp cutting surfaces

Never use a hammer on another hammer. The impact of the hardened surfaces may cause the heads to shatter

Do not carry tools in a pocket. Transport sharp tools with the blade pointing down or in a holder

Remove fasteners by pulling the tool towards the body or pushing the tool away from the face

Power Tool Safety Considerations

Follow all manufacturer‟s recommended operating instructions

Use CSA approved power tools

Do not use electrical tools on or near a wet or damp area

Use tools that are double-insulated or have a third conductor grounding terminal to provide a path for fault current

Ensure the power switch is in the OFF position before connecting to power source

Ensure that all safety guards are in place before starting

Arrange cords and hoses to prevent accidental tripping

Stand to one side when starting and using a grinder

Stand clear of operating power tools. Keep hands and arms away from moving parts

Shut off, lock out, and tagout disconnect switches of power tools requiring service

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Disassembly Activity 2

Refer to the DVD provided with the module for step by step directions to disassemble the engine correctly without damaging or loosing any parts. *Remember to always use cardboard to stick you nuts bolts and screws into as well as label them as to what component they belong to.

Activity 3 In this activity you will reassemble the engine.

Check the block and piston for correct clearances first. Follow from step 2 to step 7 recording your measurements in the spaces provided.

Cylinder Preparation

Step Action

1 Hone the cylinder using the cylinder hone and drill

Measure Cylinder

In the student shared folder under applied tech you will find a Power Point presentation on reading a micrometer. Go view and study it!

Step Action

2

Using telescoping gauge and the proper sized micrometer, measure the inside diameter of the cylinder Measure every inch (25mm) down the cylinder and again at 90°

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Record your meaurements here:

Step Action

3 Measure again at 90° every inch down the cylinder.

Record your meaurements here:

90°

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4 Measure piston skirt

Step Action

5 Measure valve stem for wear

6 Using split ball gauge, measure the valve guides

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7 Measure the three journals on the crankshaft. 1. Connecting Rod Journal 2. Flywheel Journal 3. PTO Journal

8

Lubricate cylinder and valve stems with white grease

9

Refer to the DVD for step by step instructions and tips to ensure the engine is assembled properly in the correct order. *Make sure all torque sequences and specifications are followed exactly.

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Final Questions:

Here are a few questions that bring together everything that you have learned:

1. What are the five basic systems that make up a small gas engines?

1. 2. 3. 4. 5.

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