Engines analysis

Small Engine Analysis

 

This analysis is to help you learn a systematic diagnostic process for evaluating performance of small gasoline engines. In the analysis sheet, you will find two terms, “Found” and “Should be” and/or “Reject size.” The “Found” term, is what you find when measuring the small engine parts. The “Should be” and/or “Reject Size term, is what the specification should be to run properly. From the repair manual, you will find the manufacturer’s recommendations, which you will report on this form in the “should be” and/or “reject size” term. Along with that, you will answer all the questions concerning the general condition of the small engine and parts.

 

Make of Engine: _____________________________    Model/Family: ____________________

Type: _________________________          Serial Number/Code: _________________________

 

Pre-Diagnostic Check

1. Does the engine have spark? __________.
2. Complete a compression test.         Found: ___________     Should be: __________
3. Remove the engine shroud.
4. Do a compression test by giving the flywheel a quick spin. Does the flywheel rebound sharply? ___________
5. Drain the oil and remove the spark plug.
6. Draw a complete sketch in respect to the carburetor and governor system (governor linkage, springs, etc...). Disconnect and remove air cleaner, carburetor, gas tank, and governor linkage from the engine.

1. If there is no spark, refer to Ignition System.
2. If there is no compression, refer to Compression System.
3. All must complete the Carburetion System.

Carburetion System

1. Describe the general condition of the carburetor.

1. Type of carburetor: _________________________
2. Draw a sketch of the carburetor.

 

 

1. Take apart and clean the carburetor. (Be Careful! There are many small parts).
2. General condition of the float: ________________
3. General condition of the venturi, seat, and gaskets: _________________________________
4. If the answer to questions 14 & 15 are in poor condition, replace with a carburetor repair kit.
5. Put carburetor back together. (Note the location of parts).
6. General condition of air cleaner device: ___________________________
7. If the answer to question 18 is in poor condition, remove filter and clean with appropriate solvent.
8. Replace fuel line and fuel filter, with a new parts, if it is in poor condition.

 

Ignition System

1. Remove the spark plug
2. Measure spark plug gap                 Found: _________       Should be: __________
3. General condition of spark plug: ______________________
1. Spark plug: Make: ________________, Number: _____________
4. If the answer to question 23 is poor, replace with new spark plug.
5. Measure flywheel magnet to armature air gap         Found: ___________      Should be: ________
6. If air gap is not accurate, loosen armature and reset to specified air gap.
7. General condition of the flywheel: __________________________
8. If flywheel condition is poor, clean the flywheel and magnet with emery cloth.
9. Does the engine have ignition breaker points and condenser? ___________
10. If the answer to question 29 is YES, answer questions 31 through 36. If the answer to question 29 is NO, move on to compression system.
11. Remove crankshaft screen, flywheel nut, and starter mechanism.
12. Remove flywheel
13. Condition of flywheel key: ___________________
14. Measure ignition breaker-point gap            Found: __________       Should be: _________
15. If the breaker-point gap is too small or too big, loosen beaker and reset to specified gap.
16. General condition of condenser and wiring system: _________________________________

Compression System

1. Remove the cylinder head and report the condition of the cylinder head and head gasket.

 

1. Move the piston to top dead center and measure the piston to cylinder wall clearance.

Found: __________                        Should be: __________

1. Move the piston to bottom dead center and report the condition of the cylinder wall.

1. Cylinder Wall (Measure with Telescoping Gauge & Micrometer)
1. Dimensions

-Top                      Found: ___________     Should be: __________
-Bottom                 Found: ___________     Should be: __________
-Out of round        Found: ___________     Should be: __________

1. Remove the valve cover plate.
2. Valve tappet clearance:
1. Intake:                   Found: ___________     Should be: __________
2. Exhaust:                Found: ___________     Should be: __________
3. Remove valve springs and valves. Report the general condition of each valve (stem, face, & margin). Report also the condition of the valve seat, valve springs, and valve guides. Mark each valve, so to remember which valve is the intake and exhaust valve.

 

1. Remove the crankcase cover plate.
2. Before removing parts, note the position of the timing marks on the crankshaft and camshaft gears. If the marks are not visible, use a center punch and properly mark each gear.

1. Remove the camshaft gear and valve tappets. Mark the valve tappets, so when assembling they go back in their respective bores. Explain why this is important.

 

1. Unbolt the connecting rod from the crankshaft.

1. Remove the piston from the engine block by pushing it out of the top of the cylinder.

 

1. Remove the crankshaft

1. Measure the gap between the crankpin journal and connecting rod bearing with plastigage.
1. Connecting rod torque (pound inches):       Should be: __________
2. Report the general condition of the piston skirt
3. Measure the piston ring-gap (end clearance)
1. Compression (top):            Found: __________       Should be: __________
2. Compression (center):        Found: __________       Should be: __________
3. Oil (bottom):                     Found: __________       Should be: __________

 

1. If the answer to question 52 is not within specifications, replace with new piston rings.

1. Report the general condition of the crankshaft (scoring, bent, etc…)

 

1. Measure the crankshaft journal
1. Magneto:               Found: __________       Should be: __________
2. Crank pin:             Found: __________       Should be: __________
3. PTO:                     Found: __________       Should be: __________

1. Measure the connecting rod pin bore

 

1. Piston pin:             Found: __________       Should be: __________
2. Crank pin:             Found: __________       Should be: __________

1. Measure the main bearing and seal

 

1. PTO:                     Found: __________       Should be: __________
2. Magneto:               Found: __________       Should be: __________

1. If the answer the questions 55, 56 and 57 are not within specifications, replace with new connecting rod, bearings, and seals.

 

1. List new part and their costs to repair small engine.

Quantity          Part Name                                                       Cost
______              ________________________________               __________________________
______              ________________________________               __________________________
______              ________________________________               __________________________
______              ________________________________               __________________________
______              ________________________________               __________________________
______              ________________________________               __________________________
______              ________________________________               __________________________
______              ________________________________               __________________________
______              ________________________________               __________________________
______              ________________________________               __________________________
______              ________________________________               __________________________
______              ________________________________               __________________________

Re-assembly Specifications

1. Fill out the torque table chart below:

	Should be	Should be
	Pound inches	Pound feet
Head bolts
Connecting rod bolts
Flywheel
Others:

1. Draw a sketch of the cylinder head torque sequence.

 

 

1. Repair small engine