small gas engine: disassembly - i

1

Small Gas Engine: Disassembly - I Supplement for CEV #880

Small Gas Engine: Disassembly - I

2

Supplement for CEV #880 Goal: The student is introduced to the steps necessary to properly disassemble a small gas engine. Objectives: 1. to learn fundamental safety techniques 2. to learn how to properly remove the fuel tank, air filter, carburetor, muffler, and blower housing

3. to be able to properly check engine compression and the ignition system

Small Gas Engine: Disassembly – I Quiz I

3

True or False ____ 1. All jewelry should be removed prior to working with a small gas engine. ____ 2. It is not necessary to wear safety goggles. ____ 3. In 1982, manufacturers changed from points and condenser ignitions to an electronic ignition called a magnetron. ____ 4. When testing the ignition, all kill switches should be disconnected. Multiple Choice ____ 5. After draining the oil and fuel, one should

a. dump the oil and gas in a trash can b. pour the oil and gas on the ground c. take the oil and gas to the proper recycling center d. drain the oil onto a paved road

____ 6. What is used to test the ignition?

a. spark tester b. ignition monitor c. the ignition does not need to be tested d. none of the above

____ 7. What is used to hold the engine steady during disassembly?

a. a screwdriver b. an engine stand c. adjustable pliers d. nothing

4

Small Gas Engine: Disassembly - I Quiz II

Short Answer 1. What is used to hold small parts after they have been removed from the engine? 2. Before removing the fuel tank, what must be removed first? 3. What is avoided by supporting the carburetor when it is being removed from the engine? True or False _____4. Pliers should be used to remove the carburetor linkage. ____ 5. Paper air filters may be cleaned with soapy water and reused. ____ 6. By moving the throttle, one can detect wear and tear.

5

Small Gas Engine: Disassembly - I Quiz III

Short Answer 1. How do the bolts on a muffler keep from coming unscrewed on an engine that experiences heat and vibration? 2. Mufflers are held in place by “shouldered” bolts. What do these bolts prevent? 3. An engine with the model number 124702 has a displacement of how many cubic inches? True or False ____ 4. The model, type, and code numbers represent many things such as the date the engine was manufactured, what types of decals it should have, and whether it has plain or ball bearings. ____ 5. Changing a blower housing without the correct model number can cause delays if parts are needed for the engine. ____ 6. It is important to check the rewind starter on an engine.

6

Small Gas Engine: Disassembly - I Quiz IV

Multiple Choice ____ 1. To check the compression of an engine, the flywheel should be turned in which direction? a. clockwise b. counter-clockwise c. either clockwise or counter-clockwise d. none of the above True or False ____ 2. If resistance is noticed while turning the flywheel, the engine has compression. ____ 3. Any socket can be used to remove a spark plug. ____ 4. An engine with compression will show resistance every two rotations.

7

Small Gas Engine: Disassembly - I Final Quiz

True or False ____ 1. After the oil has been drained from the engine, it should be taken to an oil recycling or disposal center. ____ 2. It is acceptable to use pliers to remove carburetor linkages. ____ 3. Engine compression is checked by turning the flywheel clockwise. ____ 4. The spark plug should be removed with a spark plug socket. Short Answer 5. What type of ignition is on engines built before 1982? 6. What type of ignition do engines have today? 7. What kind of bolts prevent the muffler from being damaged from too much torque? 8. What do the first two numbers of the model number 124702 represent? Multiple Choice ____ 9. Foam air filters are found on engines built a. before 1982 b. after 1982 c. no engine has a foam air filter d. all engines have a foam air filter ____ 10. Foam air filters may be reused if they are periodically cleansed with which of the following? a. ether solvent b. gasoline c. warm, soapy water d. carburetor cleaner

1

Small Gas Engine: Disassembly – I Answer Key for CEV #880

True or False T 1. All jewelry should be removed prior to working with a small gas engine. F 2. It is not necessary to wear safety goggles. One should always wear safety glasses when working on engines. T 3 . In 1982, manufacturers changed from points and condenser ignitions to an electronic ignition called a magnetron. T 4. When testing the ignition, all kill switches should be disconnected. Multiple Choice c 5. After draining the oil and fuel, one should a. dump the oil and gas in a trash can b. pour the oil and gas on the ground c. take the oil and gas to the proper recycling center d. drain the oil onto a paved road a 6. What is used to test the ignition? a. spark tester b. ignition monitor c. the ignition does not need to be tested d none of the above b 7. What is used to hold the engine steady during disassembly? a. a screwdriver b. an engine stand c. adjustable pliers d. nothing

2


Short Answer 1. What is used to hold small parts after they have been removed from the engine? muffin tin (Other holders might include a egg carton with lid removed, cups, old silverware partition, and other used items that hold and separate.) 2. Before removing the fuel tank, what must be removed first? shroud 3. What is avoided by supporting the carburetor when it is being removed from the engine? damaging the linkages True or False F 4. Pliers should be used to remove the carburetor linkage.

The linkages are very sensitive; using pliers might bend the wire linkage. Rotate the carburetor to drop it off the throttle linkage. Many fine linkages are better off left on the engine where they are less likely to get bent or broken.

F 5. Paper air filters may be cleaned with soapy water and reused. Foam filters can be cleaned this way; paper filters are disposable and should be discarded and replaced. T 6. By moving the throttle, one can detect wear and tear.

Small Gas Engine: Disassembly – I

3

Answer Key for CEV #880 Short Answer

1. How do the bolts on a muffler keep from coming unscrewed on an engine that experiences heat and vibration?

Tabs lock the bolts in position. 2. Mufflers are held in place by “shouldered” bolts. What do these bolts prevent? smashing the muffler 3. An engine with the model number 124702 has a displacement of how many cubic inches? 12 cubic inches True or False T 4. The model, type, and code numbers represent many things such as the date the engine was manufactured, what types of decals it should have, and whether it has plain or ball bearings. T 5. Changing a blower housing without the correct model number can cause delays if parts are needed for the engine. T 6. It is important to check the rewind starter on an engine.


4

Multiple Choice a 1. To check the compression of an engine, the flywheel should be turned in which direction? a. clockwise b. counter-clockwise c. either clockwise or counter-clockwise d. none of the above True or False T 2. If resistance is noticed while turning the flywheel, the engine has compression. F 3. Any socket can be used to remove a spark plug.

Use a socket designed for removing spark plugs—one that has a rubber insert to cushion the porcelain on the spark plug so it doesn’t break.

T 4. An engine with compression will show resistance every two rotations.


5

True or False T 1. After the oil has been drained from the engine, it should be taken to an oil recycling or disposal center. F 2. It is acceptable to use pliers to remove carburetor linkages. Pliers can damage or bend the thin linkages. T 3. Engine compression is checked by turning the flywheel clockwise. T 4. The spark plug should be removed with a spark plug socket. Short Answer 5. What type of ignition is on engines built before 1982? points and condenser 6. What type of ignition do engines have today? magnetron (electronic ignition) 7. What kind of bolts prevent the muffler from being damaged from too much torque? shouldered bolts 8. What do the first two numbers of the model number 124702 represent? the number of cubic inches of displacement Multiple Choice a 9. Foam air filters are found on engines built a. before 1982 b. after 1982

6

c. no engine has a foam air filter d. all engines have a foam air filter c 10. Foam air filters may be reused if they are periodically cleansed with which of the following? a. ether solvent b. gasoline c. warm, soapy water d. carburetor cleaner

1

Small Gas Engine: Disassembly - I Supplement for CEV #880

Small Gas Engine Disassembly - is the first in a series on the proper techniques and procedures necessary for maintaining a 5 horsepower, Briggs and Stratton Model 124702 engine. This series incorporates CEV’s VideoActive format, which creates an interactive learning environment by incorporating questions and discussion into the program. Color and numeric coding for each section make selection of a desired topic or review of specific information much easier and faster. Following each section, a short quiz is presented, and a comprehensive ten-question final quiz is presented at the end of the each program. Included in this teaching guide are corresponding copy-ready student quizzes, a teacher’s key, and an outline for performing the disassembly procedures demonstrated in this production. Skills and Practices demonstrated: In part one of this series, Dr. David Lawver, Associate Professor of Agricultural Education and Communications at Texas Tech University, will demonstrate the removal of the fuel tank, air filter, carburetor and linkage, muffler, blower housing and spark plug. Dr. Lawver will also discuss how to check the engine for proper compression and how to check the ignition system. It is recommended that this production be used with the repair and service manual published by the manufacturer. Because this production focuses on one particular engine model from Briggs and Stratton, a condensed table of specifications is provided in this guide. However, this table should not be used in place of the complete discussion found in the manufacturer’s repair manual. This teaching guide is designed to follow the material as it is presented in the production. The guide is presented in outline form so that it briefly describes the procedures performed. Next to each procedure, remarks concerning the tools that are used to complete the procedure and any special instructions are listed. This format enables the viewer to follow along with the production and it serves as a guide when performing the disassembly procedures after viewing.

2

TABLE OF ENGINE SPECIFICATIONS

(for Briggs and Stratton Model 124702 Engine) ARMATURE AIR GAP .006-.010 IN. VALVE CLEARANCE INTAKE .005-.007 IN. EXHAUST .007-.009 IN. TORQUE SPECIFICATIONS FLYWHEEL NUT 55 FT. LBS. CYLINDER HEAD 140 IN. LBS. CONNECTING ROD 100 IN. LBS. CRANKSHAFT REJECT SIZE MAG JOURNAL .873 IN. CRANKPIN JOURNAL .996 IN. PTO JOURNAL 1.060 IN. CAM GEAR JOURNAL REJECT SIZE .498 IN. CYLINDER BORE STANDARD SIZE 2.6885 (2.6875) IN. RING GAP REJECT SIZE OIL .045 IN. COMPRESSION .035 IN. SPARK PLUG GAP .030 IN. CRANKSHAFT END PLAY .002 - .030 IN. PISTON (WRIST) PIN REJECT SIZE .489 IN.

3

Small Gas Engine: Disassembly - I

Tools and equipment needed: engine stand, ignition spark tester, flat blade screwdriver, 1/4” nutdriver, speed wrench handle, small punch, plastic mallet, 7/16” socket, spark plug socket, and ratchet

_________________________________ Procedure Remarks ______________________________ _ Check ignition Use ignition spark tester; disengage all kill switches. Drain fuel and oil Retain fuel and properly dispose of used oil.

Remove fuel tank Remove shroud; use 1/4” nutdriver; use speed wrench handle. Remove air filter Use flat blade screwdriver; use 1/4” nutdriver to remove plate under air cleaner. Remove carburetor and linkages Do not bend linkages or use pliers when disconnecting; use 3/8” socket and speed wrench handle. Remove kill wire from carburetor linkage Release wire from brass tab. Check throttle shaft for wear Move shaft back and forth to determine wear. Remove muffler Use punch and plastic mallet to loosen metal locking tabs from bolts; use 7/16” socket and speed wrench. Remove blower housing Use socket and speed wrench handle; use 1/4” and check rewind starter nutdriver to remove oil fill tube and dip stick. Check compression Turn flywheel clockwise and note resistance. Remove spark plug Use spark plug socket and ratchet.

Small Gas Engine: Disassembly - II Supplement for CEV #881

i

Small Gas Engine: Disassembly - II

Supplement for CEV #881

Goal: To introduce the proper techniques needed to disassemble a small gas engine. Objectives: 1. to be able to properly remove the cylinder head, crankcase breather, valves, flywheel, and armature 2. to discuss the strokes of the 4-stroke cycle engine 3. to understand the function of the flywheel key

1

some engines, the long bolts are located around the exhaust valve.

___2. The head gasket should be left on the cylinder head after disassembly.

Small Gas Engine: Disassembly – II

Quiz I True or False ____1. In _

hort Answer S at does BDC stand for?

es TDC stand for?

____

d. 1

____

e

d. both the intake and exhaust valves are closed

troke

d. exhaust stroke

3. Wh 4. What do

ultiple Choice M

5. How many strokes does the engine have in its cycle? a. 2 b. 4 c. 6

6. During the exhaust stroke, which valve is open? a. intake valve b. exhaust valv c. both valves

____7. At which stroke does the spark plug produce ignition? a. intake stroke b. compression s c. power stroke

2

Small Gas Engine: Disassembly - II Quiz II

___1. The crankcase breather releases negative and positive pressure from the crankcase created during the compression stroke.

___2. If the exhaust valve opens early, while the intake valve is still open, the engine will have more power.

___3. The exhaust spring and keeper should remain with the exhaust valve, while the intake spring and keeper should be kept with the intake valve.

hort Answer

True or False _ _ _ S 4. If the intake valve is open too long, what happens to the air-fuel mixture?

5. How should the proper valve-to-tappet clearance be determined?

____6. When checking the valve-to-tappet clearance, the piston should set at what is nce f f the cylinder?

c. 1/2 inch

d. 1 inch

Multiple Choice

d ta rom the top o a. 1/8 inch b. 1/4 inch

3

___ ot available, it is okay to use a large screwdriver to hold the flywheel still.

st iron flywheels are used on horizontal shaft engines.

be replaced with a hardened steel ey.

inum flywheels found on vertical shaft or horizontal shaft engines?

portant not to expose the coil and armature to engine cleaning solvents?

____6. This engine has what type of ignition? denser

s

d. none of the above

Small Gas Engine Disassembly - II Quiz III

True or False _ 1. If a flywheel holder is n ____2. Ca ____3. If the flywheel key is damaged, it may k

hort Answer S 4. Are alum 5. Why is it im

ultiple Choice M

a. points and con b. spontaneou c. magnetron

4

___ ds for the point at which the piston is at the top of its travel in the cylinder.

___ e during the compression stroke would not be able to escape the engine.

at does BDC stand for?

early opening exhaust valve will do what to the power of an engine?

from the top of the cylinder when checking valve-to-tappet clearance?

at are the four strokes of a 4-stroke cycle engine?

ition occurs during which stroke?

d flywheel key is found, it should be replaced with which of the following?

y for the engine

d. there is no need to replace flywheel keys

Small Gas Engine: Disassembly - II Final Quiz

rue or False T _ 1. TDC stan _ 2. Without the crankcase breather, pressure created in the crankcas

hort Answer S 3. Wh 4. An 5. At what distance should the piston be 6. Wh 7. Ign

ultiple Choice M ____8. If a damage

a. any flywheel key b. a flywheel key made specificall c. a hardened steel flywheel key

5

____

d. neither vertical nor horizontal shaft engines

____ to stabilize the flywheel for removal, which of the following should be used?

r

c. either a or b are acceptable

9. Which of the following have aluminum flywheels?

a. vertical shaft engines b. horizontal shaft engines c. both vertical and horizontal shaft engines

10. In order

a. a large screwdrive b. a flywheel holder

1

Small Gas Engine: Disassembly – II

Answer Key for CEV #881 True or False T 1. In some engines, the long bolts are located around the exhaust valve. F 2. The head gasket should be left on the cylinder head after disassembly. The old gasket should be removed, all gasket material should be scraped from the cylinder head, and a new gasket should be applied. Short Answer 3. What does BDC stand for? Bottom Dead Center

4. What does TDC stand for? Top Dead Center

Multiple Choice b 5. How many strokes does the engine have in its cycle? a. 2 b. 4 c. 6 d. 1 b 6. During the exhaust stroke, which valve is open? a. intake valve b. exhaust valve c. both valves d. both the intake and exhaust valves are closed c 7. At which stroke does the spark plug produce ignition? a. intake stroke b. compression stroke c. power stroke d. exhaust stroke

2

Small Gas Engine: Disassembly – II Answer Key for CEV #881

True or False T 1. The crankcase breather releases negative and positive pressure from the crankcase created during the compression stroke. F 2. If the exhaust valve opens early, while the intake valve is still open, the engine will have more power. If this happens, the engine can’t produce the normal power; it loses power through the exhaust system. T 3. The exhaust spring and keeper should remain with the exhaust valve, while the intake spring and keeper should be kept with the intake valve. Short Answer 4. If the intake valve is open too long, what happens to the air-fuel mixture? it escapes out into the carburetor 5. How should the proper valve-to-tappet clearance be determined? Consult the manufacturer’s repair manual. Multiple Choice b 6. When checking the valve-to-tappet clearance, the piston should set at what distance from the top of the cylinder? a. 1/8 inch b. 1/4 inch c. 1/2 inch d. 1 inch

3

Small Gas Engine: Disassembly – II Answer Key for CEV #881

True or False F 1. If a flywheel holder is not available, it is okay to use a large screwdriver to hold the flywheel still.

It’s important to use the proper tool, because a screwdriver can break off the flywheel fins.

T 2. Cast iron flywheels are used on horizontal shaft engines. F 3. If the flywheel key is damaged, it may be replaced with a hardened steel key.

Replace only with an manufacturer’s approved key. The key is designed to serve as a protector—it breaks first under stress, thus causing the engine to stop. If they key did not break, the engine parts would most likely break, and it is cheaper and easier to replace a flywheel key than a flywheel or crankshaft.

Short Answer 4. Are aluminum flywheels found on vertical shaft or horizontal shaft engines? vertical shaft engines 5. Why is it important not to expose the coil and armature to engine cleaning solvents? Plastic parts and resin could become damaged. Multiple Choice c 6. This engine has what type of ignition?

a. points and condenser b. spontaneous c. magnetron d. none of the above

4

Small Gas Engine: Disassembly - II Answer Key for CEV #881

True or False T 1. TDC stands for the point at which the piston is at the top of its travel in the cylinder. T 2. Without the crankcase breather, pressure created in the crankcase during the compression stroke would not be able to escape the engine. Short Answer 3. What does BDC stand for? Bottom Dead Center 4. An early opening exhaust valve will do what to the power of an engine? The engine will lose power. 5. At what distance should the piston be from the top of the cylinder when checking valve-to-tappet clearance? 1/4” from the top of the cylinder 6. What are the four strokes of a 4-stroke cycle engine? Intake, compression, power and exhaust

7. Ignition occurs during which stroke? power stroke

Multiple Choice b 8. If a damaged flywheel key is found, it should be replaced with which of the following?

a. any flywheel key b. a flywheel key made specifically for the engine c. a hardened steel flywheel key d. there is no need to replace flywheel keys

5

a 9. Which of the following have aluminum flywheels? a. vertical shaft engines b. horizontal shaft engines c. both vertical and horizontal shaft engines d. neither vertical nor horizontal shaft engines

b 10. In order to stabilize the flywheel for removal, which of the following should be used?

a. a large screwdriver b. a flywheel holder c. either a or b are acceptable

1



Small Gas Engine Disassembly - II is the second in a three-part series on the proper techniques and procedures necessary for the disassembly of a 5 horsepower Briggs and Stratton Model 124702 engine. This series incorporates CEV’s VideoActive format, which creates an interactive learning environment by incorporating questions and discussion into each program. Color and numeric coding for each section make selection or review of a topic much easier and faster. Following each section, a short quiz is presented, and a comprehensive quiz ends the program. Included in this teaching guide are corresponding copy-ready student quizzes, a teacher’s key, and an outline for performing the demonstrated disassembly procedures. Skills and Practices Demonstrated: Dr. David Lawver, Associate Professor of Agricultural Education and Communications at Texas Tech University, shows how to check the armature air gap settings and demonstrates the removal of the cylinder head, crankcase breather, valves and springs, flywheel and armature. Dr. Lawver also discusses the strokes of a 4-stroke cycle engine and how to check valve-to-tappet clearance and inspect the flywheel key. Use this production in conjunction with the repair and service manual published by the manufacturer. Because this production focuses on one particular engine model from Briggs and Stratton, a condensed table of specifications is provided in this guide. However, this table should not be used in place of the complete discussion found in the manufacturer’s repair manual. This teaching guide is designed to follow the material as it is presented. The guide is presented in outline form so that it briefly describes the procedures performed. Next to each procedure, remarks concerning the tools that are used to complete the procedure and any special instructions are listed. This format enables the viewer to follow along and it serves as a guide when performing the disassembly procedures after viewing.

2



3


Tools and equipment needed: thickness gauge, 1/4” nutdriver, 1/2” socket, ratchet, speed wrench handle, valve spring compressor, large flat blade screwdriver, flywheel holder, 15/16” socket, break over handle, plastic mallet, flywheel puller.

_________________________________ Procedure Remarks _________________________________ Check armature air gap Use thickness gauge; flywheel magnet should be aligned with the armature. Move armature away from flywheel Rotate flywheel until magnets are away from the armature; loosen bolts, lift armature and retighten bolts. Remove cylinder head and gasket Note any difference in length of bolts and their location when removing; use 1/2” socket on ratchet, then speed wrench handle; remove head gasket. Remove crankcase breather Use speed wrench handle with socket Check valve-to-tappet clearance Use thickness gauge; measure both intake and exhaust tappet clearance; piston should be 1/4” down on the power stroke. Remove valves and springs Use valve spring compressor or large flat blade screwdriver; keep valve springs and keepers with corresponding valve. Remove clutch assembly and flywheel Use flywheel holder, 15/16” socket and break over handle to loosen flywheel nut; apply pressure to flywheel and tap crankshaft with plastic mallet or use appropriate flywheel puller. Inspect flywheel key for damage Key may be partially sheared.

4

Remove armature Disconnect kill wire attached to flywheel brake; use 1/4” nutdriver; flywheel magnets should be rotated away from armature.

Small Gas Engine: Disassembly - III Supplement for CEV #882

i

Small Gas Engine: Disassembly - III


Goal: To introduce the correct steps needed to disassemble a small engine. Objectives: 1. to learn the proper methods of removing the sump, camshaft, piston, and crankshaft 2. to learn how to properly remove the rings and wrist pin from the piston

1

Small Gas Engine: Disassembly – III

Quiz I True or False ____1. Crankshaft end play should be checked with a dial indicator before removing the sump. Short Answer 2. Before removing the sump, it is advised to do what to the crankshaft in order to avoid damaging the oil seal? Multiple Choice ____3. Rust may be removed from the crankshaft using which of the following?

a. sandpaper b. solvent c. emery cloth d. it is not necessary to remove the rust

____4. After removing the bolts from the sump, the sump should be tapped off using which of the following?

a. ball-peen hammer b. hammer and chisel c. any hammer d. plastic mallet

2

Small Gas Engine: Disassembly - III Quiz II

True or False ____1. The orange oil slinger is very important in keeping the crankcase lubricated. ____2. The crank gear is two times larger than the cam gear. ____3. The mechanical governor is activated by small flyweights which move a small piston which then slows the engine down. Short Answer 4. What part of the camshaft moves the tappets up and down? 5. Today, many parts are durable and lightweight because they are made of what?

3

Small Gas Engine: Disassembly - III Quiz III

True or False ____1. A piston ring may be removed by expanding it with the fingers and pulling it off. ____2. The top ring on the piston is known as the oil ring. Short Answer 3. What is unique about the bolts which connect the rod cap to the piston rod in this engine? 4. What are the three journals on the crankshaft? 5. What must first be removed in order to remove the wrist pin from the connecting rod? Multiple Choice ____6. How can the crankshaft be checked for straightness?

a. roll it over a level surface as demonstrated b. place in a drill press c. attach it to a lathe d. all of the above

____7. How many rings are on the piston?

a. 1 b. 2 c. 3 d. 4

4

Small Gas Engine: Disassembly - III Final Quiz

True or False ____1. Emery cloth is used to remove rust from the crankshaft. ____2. The cam gear is two times larger than the crank gear. ____3. Plastic parts are very durable and lightweight. ____4. The oil slinger is not important to the engine and can be left out. Short Answer 5. If the crankshaft is not cleaned before removing the sump, what might happen to the oil seal? 6. What part of the camshaft moves the tappets up and down? 7. Name the three journals on the crankshaft. 8. How does the mechanical governor work? Multiple Choice ____9. Where is the oil ring located on the piston?

a. top b. middle c. bottom d. there is no such thing as an oil ring

____10. A dial indicator is used to measure which of the following?

a. crankshaft end play

5

b. valve-to-tappet clearance c. journals on the crankshaft d. journals on the camshaft

1


Answer Key for CEV #882

True or False T 1. Crankshaft end play should be checked with a dial indicator before removing the sump. Short Answer 2. Before removing the sump, it is advised to do what to the crankshaft in order to avoid damaging the oil seal? Clean the crankshaft with emery cloth to remove the rust. Multiple Choice c 3. Rust may be removed from the crankshaft using which of the following?

a. sandpaper b. solvent c. emery cloth d. it is not necessary to remove the rust

d 4. After removing the bolts from the sump, the sump should be tapped off using which of the following?

a. ball-peen hammer b. hammer and chisel c. any hammer d. plastic mallet

2



True pr False T 1. The orange oil slinger is very important in keeping the crankcase lubricated. F 2. The crank gear is two times larger than the cam gear.

The cam gear is two times larger (has twice as many teeth) than the crank gear; that means the crank gear will turn twice for every single revolution of the cam gear.

T 3. The mechanical governor is activated by small flyweights which move a small piston which then slows the engine down. Short Answer 4. What part of the camshaft moves the tappets up and down? the lobes 5. Today, many parts are durable and lightweight because they are made of what? plastic

3



True or False T 1. A piston ring may be removed by expanding it with the fingers and pulling it off. F 2. The top ring on the piston is known as the oil ring. compression ring Short Answer 3. What is unique about the bolts which connect the rod cap to the piston rod in this engine? They are double hex-headed. 4. What are the three journals on the crankshaft? magneto, crankpin, and power take-off (PTO) journals 5. What must first be removed in order to remove the wrist pin from the connecting rod? the keeper ring Multiple Choice d 6. How can the crankshaft be checked for straightness?

a. roll it over a level surface as demonstrated b. place in a drill press c. attach it to a lathe d. all of the above

c 7. How many rings are on the piston?

a. 1 b. 2 c. 3 d. 4

4

Small Gas Engine: Disassembly – III Answer Key for CEV #882

True or False T 1. Emery cloth is used to remove rust from the crankshaft. T 2. The cam gear is two times larger than the crank gear. T 3. Plastic parts are very durable and lightweight. F 4. The oil slinger is not important to the engine and can be left out. The oil slinger makes sure all the internal engine parts are lubricated. Short/Answer 5. If the crankshaft is not cleaned before removing the sump, what might happen to the oil seal? may be damaged or torn 6. What part of the camshaft moves the tappets up and down? lobes 7. Name the three journals on the crankshaft. magneto, crankpin, and power take-off (PTO) journals 8. How does the mechanical governor work?

Small flyweights move a small piston which causes the engine to slow down.

Multiple Choice c 9. Where is the oil ring located on the piston? a. top b. middle c. bottom d. there is no such thing as an oil ring a 10. A dial indicator is used to measure which of the following? a. crankshaft end play b. valve-to-tappet clearance c. journals on the crankshaft d. journals on the camshaft

1


Supplement for CEV #882 Small Gas Engine Disassembly - III is the third in a three-part series on the proper techniques and procedures necessary for the disassembly of a 5 horsepower Briggs and Stratton Model 124702 engine. This series incorporates CEV’s VideoActive format, which creates an interactive learning environment by incorporating questions and discussion into each program. Color and numeric coding for each section make selection or review of specific information easier and faster. Following each section, a short quiz is presented, and a comprehensive final quiz is presented at the end. The teaching guide contains copy-ready student quizzes, a teacher’s key, and an outline for performing the demonstrated disassembly procedures. Skills and Practices Demonstrated: Dr. David Lawver, Associate Professor of Agricultural Education and Communications at Texas Tech University, demonstrates checking crankshaft end play and removal of the sump, oil slinger, camshaft, tappets, piston and crankshaft. Dr. Lawver also discusses operation of the mechanical governor, then completes the disassembly procedure with the removal of the rings and connecting rod from the piston. Because this production focuses on one particular engine model from Briggs and Stratton, a condensed table of specifications is provided in this guide. However, no part of this multimedia should be used in place of the complete discussion found in the manufacturer’s repair manual. This teaching guide follows the material presented. An outline form briefly describes the procedures performed, along with tools that are used to complete the procedure and any special instructions. This format enables the viewer to follow along and it serves as a guide when performing the disassembly procedures after viewing.

2



3

Small Gas Engine Disassembly - III

Tools and equipment needed: dial indicator, 3/8” socket, speed wrench handle, plastic mallet, ratchet, long nose pliers, punch Procedure Remarks Check crankshaft end play Use dial indicator. Remove rust or burrs from crankshaft Use emery cloth. Remove sump Use 3/8” socket and speed wrench handle; use plastic mallet to remove sump. Remove oil slinger Lift from camshaft. Remove camshaft Tappets should remain in proper position before removing camshaft. Remove tappets Mark exhaust tappet with an “X”. Remove rod cap Use socket and ratchet; note position or alignment grooves when removing. Remove piston Remove any ridge on the inside of the cylinder with emery cloth; turn crankshaft until piston is at top of travel, continue rotating crankshaft until free of connecting rod, then push up on the connecting rod and lift piston out. Note notch on top of piston The notch should always face up on a vertically shafted engine. Remove crankshaft Pull crankshaft straight out. Check crankshaft for straightness Rotate on level stand, chuck magneto end in drill press or place in a lathe. Remove rings Use fingers and stretch slightly; do not break rings. Remove wrist pin Metal tab on connecting rod should align with notch on top of piston; use long nose pliers and

4

remove keeper ring; use punch and plastic mallet to tap out wrist pin.

Small Gas Engine: Disassembly Supplement for DVD CEV80880

Small Gas Engine Disassembly: Web Links CEV is not responsible for linked websites. Opinions therein are not necessarily those of CEV. Sites are offered

in good faith as potentially useful sources of current information, based upon the best data known to CEV at publishing time, and should be used under teacher supervision.

Disassembly of Lawn Mower Engine http://www.lawn-mower-shop.com/titlesli.htm Small Engines http://www.small-engines.com Briggs and Stratton Engines http://www.briggsandstratton.com Tecumseh Engines http://www.tecumseh.com Kohler Engines http://www.kohlerengines.com Kawasaki http://www.kawasaki.com/ Do It Yourself Network: Engine Projects http://www.diynet.com/DIY/projectIndexDetail/0,2041,AUTO_1387,FF.html Tractor Manuals http://www.tractor-manuals.com Small Tractor FAQ http://www.andrew.cmu.edu/user/kb13/maint_sb.htm Tractor Maintenance Record Keeping http://www.farmideas.co.uk/guide/yoursforfree.HTM Do It Yourself Guide http://www.jackssmallengines.com/do_it_home.html

http://www.lawn-mower-shop.com/titlesli.htm

http://www.small-engines.com/

http://www.briggsandstratton.com/

http://www.tecumseh.com/

http://www.kohlerengines.com/

http://www.kawasaki.com/

http://www.diynet.com/DIY/projectIndexDetail/0,2041,AUTO_1387,FF.html

http://www.tractor-manuals.com/

http://www.andrew.cmu.edu/user/kb13/maint_sb.htm

http://www.farmideas.co.uk/guide/yoursforfree.HTM

http://www.jackssmallengines.com/do_it_home.html

small gas engine: disassembly - i

Documents