Small engine maintenance and repair

SMALL ENGINE MAINTENANCE AND REPAIR

LESSON OBJECTIVES:

1) Identify tools needed for engine maintenance and repair orally with 100% accuracy.

2) Demonstrate the basic maintenance procedures required for small engines in the lab with 95% accuracy.

3) Explain the procedures for repairing the systems of a small engine on a written quiz with 90% accuracy.

4) Establish troubleshooting techniques using sequential procedure in the lab with 95% accuracy.

MYSTERY TOOLS?

1. Have you ever seen any of these before?2. What are they?3. Are they the same?4. Can you guess what the function of these tools might provide?

REASONS TO LEARN1) Why is it important to be able to identify tools needed for engine

maintenance and repair?

2) Why is it important to be able to demonstrate the basic maintenance procedures required for small engines?

3) Why is it important to be able to explain the procedures for repairing the systems of a small engine?

4) Why is it important to be able to establish troubleshooting techniques using sequential procedure?

QUESTIONS TO ANSWER1) What do we need to know in order to be able to identify tools

needed for engine maintenance and repair?

2) What do we need to know in order to be able to demonstrate the basic maintenance procedures required for small engines?

3) What do we need to know to be able to explain the procedures for repairing the systems of a small engine?

4) What do we need to know to be able to establish troubleshooting techniques using sequential procedure?

TOOLSBasic Hand Tools:

Standard wrenches sizes ¼ through 1 in. Metric wrenches sizes 6 through 24 Needle nose pliers Locking jaw pliers Standard and metric hex wrenches Phillips head screw drivers Standard screw drivers Ball peen hammer Chisels Punches

TOOLS Specialty Tools:

Flywheel wrench or Strap wrench

Flywheel puller Three jaw puller Torque wrench Micrometer Telescoping gauge Compression gauge Spark tester Ring expander Ring compressor

Valve grinding tool Cylinder hone Spark plug gaper Spring compressor Pick set Magnetic pickup tool

DEMONSTRATING BASIC MAINTENANCE PROCEDURES Read and follow all service publication instructions!

Service manuals are a student’s best friend. Read! Read! Read! When in doubt read again.

SHOP SAFETY AND SMALL ENGINES • Safety glasses must be worn

at all times.

• Keep hands and feet away from all moving parts during operation.

• Keep all ignition sources away from the work area.

• Stop engine and allow it to cool before refueling.

• Handle gasoline outdoors if possible.

• Disconnect the spark plug lead when making adjustment to prevent accidental start-up.

• Never disengage any of the safety equipment or devices.

SHOP SAFETY AND SMALL ENGINES

• Keep all shields in place.

• Do not operate engines above the specified speed.

• Never overload engines or force equipment beyond it the designed capacity.

• Never use gasoline as a solvent to clean parts.

• Only start and run engines where ventilation is adequate, preferably outdoors.

• Never pour gasoline or oil on the ground or down a drain, dispose of it in the correct container to be recycled.

BASIC MAINTENANCEAir filters can become clogged over time and should be changed (Never! Blow out an air filter with compressed air!) This can damage the filter and cause immediate engine damage.

BASIC MAINTENANCEFuel filters can also become clogged over time and should be changed (Never! Blow out a fuel filter with compressed air!) This can damage the filter and cause immediate engine damage.

OLD NEW

BASIC MAINTENANCETanks & valves can also become clogged over time however these items can be clean with solvent and blown out with low volume compressed air.

BASIC MAINTENANCECarburetors can be adjusted although it is rarely necessary. Commonly small engines are factory preset and will not acquire adjustment. However, in the case that adjustment is necessary there are usually 3 adjustment points on a carburetor.

BASIC MAINTENANCE1. Main mixture adjustment screw- this screw adjusts the fuel to

air mixture ratio by allowing more or less liquid fuel into the carburetor to mix with air to be combusted.

2. Idle mixture adjustment screw- this screw adjusts the idle air to fuel mixture.

3. Idle Speed adjustment screw- this screw adjusts the idle speed by changing the position of the throttle valve.

2.

1.

3.

BASIC MAINTENANCELubrication is very important it is necessary to deduce whether or not the engine has a pressurized lube system or not. This is a simple deduction.1. Pressurized systems- utilize the use of an oil filter 2. Non-pressurized- does not utilize an oil filter.

BASIC MAINTENANCE Different engines require different oils of different viscosities. Viscosity- is the thickness of the oil

Many non-pressurized engines call for non-detergent, single viscosity oils such as ND30

Many pressurized engines call for multi-viscosity oils such as 10w30

Multi-viscosity- is the thickness of the oil at different operating temperatures

Dip sticks must also be located and checked regularly according to service manual.

BASIC MAINTENANCECooling system- usually can be blown out with compressed air in air cooled and liquid cooled applications. May require coolant checks for adequate level and ratio in liquid cooled applications.

Air Cooled Liquid Cooled

BASIC MAINTENANCEElectrical system- somewhat maintenance free with the exception of the spark plug and a few switches which requires replacement at implied intervals.

REPAIR PROCEDUREKIS- Keep It Simple, Always check the easy things first. If an engine suddenly stops running, chances are the solution is an easy fix.

As we learned in the previous chapter the principles of operation must happen sequentially for an engine to run. If one or more of these steps are incomplete the engine will fail to run.

REPAIR PROCEDUREWe must know how to use specialty tools like:• Micrometer- measuring tool used

to check components for wear• Telescoping Gauge- t-shaped tool

used to measure cylinder wear• Plastigage- threadlike material

used to measure connecting rod bearing clearance

• Torque wrench- used to tighten fasteners to specific tolerances

• Ring-compressor- used to compress piston rings for piston installation

• Flywheel wrench or strap wrench- used to hold flywheel to remove nut

• Flywheel puller- used to pull stuck flywheels

• Spark tester- used to safely test spark

• Spring compressor- used to compress valve springs

• Feeler gauge- used to check clearances

• Valve grinder- used to grind and lap valves

TROUBLESHOOTINGCheck for spark. If the engine cranks but will not start it may not be firing. Use a spark tester to identify spark. Lack of spark may be a faulty plug, armature coil, breaker points, or ground switch

TROUBLESHOOTINGCheck for fuel. Make sure there is plenty of fuel in the tank and that the fuel is fresh. Remove the fuel line from the carburetor to be sure that the fuel flows freely from the tank, through the line and into the carburetor. If it doesn’t you must find the blockage and remove it.

TROUBLESHOOTINGAfter cranking several times and no start remove the spark plug and examine it.

• Dry- you have a fuel delivery issue inside the carburetor.

• Extremely wet- the carburetor is flooding the engine.

wetdry

TROUBLESHOOTINGIf you have spark and fuel but the engine fails to start or sounds like it is backfiring or is hard to crank, the flywheel key could be to blame.

• A flywheel key is designed to take the brunt of a blow if the engine is stopped abruptly.

• If the key is sheared the timing will be affected because it adjusts the position of the permanent magnet found in the flywheel

• This adjustment causes the spark plug to fire at the wrong time hence the backfiring or no start condition.

TROUBLESHOOTINGWhen all of the above methods have been exerted and found to be ineffective, you should run a cylinder compression test. Compression test results will act as a guide and let you know which route to take.

• If the compression tests well then the prior steps may need to be repeated because you may have missed something simple.

• If the compression tests badly then the repair may have just gotten more costly.

TROUBLESHOOTINGEngines lose compression for three primary reasons:

1. Wear and tear

2. Blown head gasket

3. Off timing

In no-tolerance engines if timing is off the piston could come in contact with the valves and cause serious component damage.

SUMMARY1) What do we need to know in order to be able to identify tools

needed for engine maintenance and repair? Basic hand tools and specialty tools

2) What do we need to know in order to be able to demonstrate the basic maintenance procedures required for small engines?

 Read and follow all service publication instructions!Service manuals are a student’s best friend. Read! Read! Read!When in doubt read again. Shop safety and small engines, we must also be concerned with the basic maintenance items: filters, lubes, dipsticks, etc.

SUMMARY3) What do we need to know to be able to explain the procedures for repairing the

systems of a small engine? KIS- Keep It Simple, Always check the easy things first. If an engine suddenly stops running, chances are the solution is an easy fix.We must know how to use specialty tools like:• Micrometer- measuring tool used to check components for wear• Telescoping Gauge- t-shaped tool used to measure cylinder wear• Plastigage- threadlike material used to measure connecting rod bearing

clearance• Torque wrench- used to tighten fasteners to specific tolerances• Ring-compressor- used to compress piston rings for piston installation• Flywheel wrench or strap wrench- used to hold flywheel to remove nut• Flywheel puller- used to pull stuck flywheels• Spark tester- used to safely test spark• Spring compressor- used to compress valve springs• Feeler gauge- used to check clearances• Valve grinder- used to grind and lap valves

SUMMARY4) What do we need to know to be able to establish troubleshooting

techniques using sequential procedure? 1. Check for spark.2. Check for fuel.3. Check for compression.4. Do not disassemble engine unless absolutely necessary!