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Wrenshall

School District

Small Engines
Small Engines Syllabus

 

Wrenshall Schools 
Mr. Gustafson 

Small Engines Syllabus 

Overview- 
This class is geared to teach students about the systems that make up small Engines. Students will learn about the cooling, ignition, compression system, and basics of operation. Students will participate in weekly lectures and demonstrations as well as lab work. 

Grading and attendance- 
Students will have 6 tests throughout the semester as well as a final test. Other graded projects will be student’s lab manuals which will be graded throughout the semester. Students will also be graded on participation and attendance. 

Classroom rules- 

Students will be expected to follow all safety rules at all times. Failure to do so can lead to removal from class. 

Respect is the number one rule in my classes- 
Respect for yourself in making positive choices in the classroom setting. 
Respect for your classmates 
Respect for your instructor 
Respect for the learning environment. 


 

sample Lab activity

 

Name __________________________ Engine # __________ 
Disassembly sheet for small engines. 
Engine Make _____________________ 
Model # _________________ 
HP _________ 
Serial # _____________________ 
As you take engine apart be sure and keep track of al parts including bolts, nuts, washers, wires and springs!!! 

1. Remove all gasoline from engine _________ 

2. Remove spark plug and check gap, what is the recorded gap?? ________ What is it supposed to be? ________ 

3. Check engine for compression PSI reading ________ 

4. Check for Spark Yes _______ No _______ 

5. Drain oil from crankcase. _Book #________________ 

6. Clean off exterior of engine.. 
7. Remove rewind and any heat shrouds on engine , Sketch how shroud goes on. 
8. Draw and sketch any carburetor linkage on back of paper #2, remove carburetor from engine. Book # _______ 
9. Remove governor air van linkage, or mechanical linkage from engine. Book #_____ Sketch a picture of what the linkage looks like on back of sheet #2 
10. Remove muffler, if you can Book #____________ 
11. Remove valve cover Book #___________ 
12. Remove spark plug and check gap. Book # ___________ 
13. Remove cylinder head and gasket. _________ 
14. Measure and record bore and stroke.Measured Bore _____ Measured stroke ________ Book Bore ______ book Stroke ____ 
15. Calculate engine Displacement ______ 
16. Check and record valve clearance. Intake clearance________ Exhaust clearance ____Book Clearance for Intake ______ Book clearance for exhaust ______. 


List the steps for checking valve clearance below. 







17. Record armature air gap. Page # _______ Measured gap_____ Book Gap _______ 

18. Remove starter clutch or flywheel nut. Page # _____ 

19. Remove flywheel, what is the flywheel puller #? Page Number _____ Part # ______ 

20. Remove breaker point ignition cover if equipped, Check condenser gap _______ 

21. Remove condenser cam and plunger if equipped. 

22. Remove magneto assemble CAREFUL these wires are gentle. Page # ________ 

23. Remove all rust and burrs from end of crankshaft with some sand paper. 

24. Remove crankcase cover. Page #_________ 

25. Check timing marks. Page #_________ 

26. Remove camshaft oil slinger and tappets. 

27. Measure camshaft lobes and seats. 
Cam lobe measurements ________ _________ Book says ______ 
Seat measurements _______ ________ book says ______ 

28. Remove rod end cap, MARK WITH A PIECE OF TAPE HOW IT GOES ON!! Page #_______ 

29. Remove piston from cylinder check the following. 
Ring land wear. Oil ____ Wiper ____ compression ____ Book says ______ Page # ___ 

30. Remove rings from piston and measure the following. 
Ring end gaps- Oil ____ Wiper _____ Compression ____ Book says. __ Page # 
Cylinder Taper ________ Book says ________ 
Cylinder out of round __________ Book says ________ Page # _________ 

31. Remove crankshaft and measure the following. 
PTO Journal _______ Crank pin Journal_______ Magneto Journal ______ 
Book says __________ __________ _______ 

32. Remove valves and springs. __________ 
Exhaust stem Diameter. ______ Intake stem Diameter _____ 
Valve margin Exhaust _______ Intake _________ valve face-Exhaust___ Intake ___ 

33. Remove Piston pin and measure Diameter. ____ Book Says____ Page # ____ 

35. Clean all parts with parts washer. 

Reassembly steps.. 

1. Check valves and seats, clean off excess carbon. 

2. Install valves, oil valve stems lightly. 

3. Test with water, Leak _____ No Leak _______ Dry engine completely when finished. 

4. Install crankshaft oil all three journals. 

5. Reinstall rings and piston pin. Page #________ 

6. Oil cylinder walls and install piston and rod assembly facing the correct direction. Page # ______ 

7. Torque connecting rod down to correct torque, bend down any retainer flips.. Torque spec.._______ 

8. Install tappets and camshaft and oil slinger aligning timing marks. 

9. Line up mechanical governor correctly. Page #_______ 

10. Install crankcase gasket, if none is present put a thin layer of silicone down. Only install 2 bolts and check crankshaft endplay adjust with cardboard spacers if needed. If acceptable install remaining bolts. 
Torque specs ________ end play measured _______ Bookend play ______ Page # ___ 

11. Install valve cover with gasket, if you have no gasket a light bead of silicone will do. 
12. Install head and gasket, torque down to correct specs. Torque specs ______ 

13. Reinstall ignition system, (breaker point if equipped. ) set to correct gap. 

14. Install flywheel key and flywheel, torque to correct specs. Torque specs ______ 

15. Reinstall armature, and set to correct gap. What is correct gap?____ 

16. Reconnect carburetor and any governor linkages Install muffler and any air baffles, install blower housing. 

17. Install fuel lines, fill with oil, How much oil is acceptable _____ Page # ___ 

18. Check compression and spark, Compression ____ spark ______ 

19. Start engine mount down to engine mount. Run date ______________ 



 

Sample Lecture

 

Cooling System Lecture- Auto 

Question- What is the Primary job of the cooling system? 

-Answer- Keep combustion chamber at optimum temp 

Fun Facts- Engine Temps can reach up to 4500degrees Fahrenheit- Average is around 2000, Melting Temp of Aluminum is around 1225 degrees. 

Liquid Vs. Air cooled Engines- Most vehicles are cooled by liquid and most small engines are cooled by air, why?? 


What are some parts of the cooling system, can you name them? 






The cooling system performs 4 functions when it comes to handling engine heat what are they? 

1. 
2. 
3. 
4. 

Absorption- the coolant absorbs the heat from the engine block. (conduction) 
Circulation- it circulates the heat to the radiator 
Radiation- It gets rid of its heat through radiating heat from the cooling fins. (convection) 
Control- The cooling system controls the temperature of the engine by controlling the amount of heat that is circulating in engine. 

Parts of the cooling System---- 
Water Pump- Usually mounted in the front of engine and run off of a belt. Responsible for circulating coolant throughout the system. 

Thermostat- 
Responsible for regulating the amount of fluid flowing in the engine block, regulating engine temperature- very important. 
The thermostat has a wax pellet that melts at a certain temperature, when it melts a spring forces the system open to allow coolant to circulate. Thermostats are set to open at certain temperatures depending on the engine. 

If engine is too hot- 
-Oil becomes thinner and does not protect as well/ can also break down. 
-Excessive temps can cause engine parts to expand 
-Detonation or pre-ignition can occur when engine is too hot-(when fuel air mixture ignites early) 


If engine too cold- 
-Poor fuel economy 
-Increased blowzy when engine is cold because piston rings do not conform to cylinder walls. 
-Cars computer feedback might not work 
-Greater pollution due to poor fuel consumption 

Water Jackets- 
Passages around cylinders that allow coolant too circulate freely and absorb heat from engine. 

Radiator- 
Radiators are where the hot coolant goes to cool off through the process of convection; coolant circulates through small passages in order to increase surface area. Two types of radiators- down flow and cross flow 
Down flow the coolant circulates down, cross flow the coolant circulates across. Why are these two types??? 

Fans- 
Fans increase air flow – only run at certain times depending on when they are needed. Either runs by a belt or an electric motor, question- what is the deciding factor of which way a fan can be run?? 
Answer- Engine orientation 

Radiator cap- 
Pressurizes cooling system- Pressurizing the system does two things it makes the coolant flow better, and it raises the boiling temperature of the coolant, 
Every pound of pressure raises boiling temperature 3 degrees. 

Also radiator cap allows a place for coolant to go when it is too hot, when coolant heats up it expands, causing pressure to grow in system. There is a spring in radiator cap that opens at a certain psi allowing coolant to go to a holding tank. When cooling system cools it creates a vacuum that lets coolant back into the radiator. 

Coolant- 
Coolant has many characteristics that make it unique. 
It has agents that lower the freezing temperature- clean out cooling system- prevent corrosion. Raises the boiling temperature also. 

Generally good to mix coolant 50 percent water to coolant. 
Straight coolant does not absorb heat as well as water and coolant. 

Heater core- 
Smaller version of radiator- allows coolant to pass through it, a fan blows on it to extract the heat. It also helps engine to cool because it gives more area for coolant to circulate. 

 

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