SMALL ENGINE DISASSEMBLY &
REASSEMBLY
Xavier J. Leslie
Professor Aaron Adams, Engineering Technology
Building, Alabama A&M
NOVEMBER 30, 2016
GROUP TWO
CRN: 72054
Table of Contents
Title Page…………………………………………….………………………………………...0
Abstract……………………………………………….…………………………………….….1
Table of contents……………………………………….……………………………………....1
List of figures………………………………………….……………………………………….2
Objectives……………………………………………….……………………………………...3
Introduction…………………………………………….……………………………………....3
Description of equipment and materials used………….………………………………………3
Experimental procedure……………………………….……………………………………......4-7
Results………………………………………………….………………………………………6
Discussion……………………………………………………………………………………...7
Conclusions…………………………………………………………………………………….7
References……………………………………………………………………………………...7
1
Abstract
The purpose of the lab on November 9, 2016 was to follow step by step instructions to
disassemble and reassemble a Briggs & Stratton model # 9T602 small lawn mower engine. The
instructions were provided form the M.E. 101 Laboratory book designated for the class.
Participants were tasked with removing the air filter, blade engagement cover, top cover, spark
drive, cylinder head, fuel tank, carburetor, blade, crank case, piston, flywheel, and crankshaft.
Tools to remove the various parts were provided and a board was custom made to facilitate the
parts of the small engine when it was fully disassembled. In addition to familiarizing oneself
with the equipment, students also were able to learn to work as a team to solve problems and
what problems arise when people work as a group. The experiment took the group a total of
about two hours to complete, one hour and fifteen minutes to disassemble and forty-five to
reassemble the lawn mower engine.
List of Figures
Figure 1. Serial Number
Figure 2. Empty Engine case
Figure 3. Disassembled Engine
Figure 4. Top Cover
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Figure 5. Model Number
Figure 6. Reassembled Lawn Mower
Figure 7. Organization Board
Figure 9. Organization Board(Empty)
Objectives
1. Completely disassemble/reassemble small engine
2. Record time, place, temperature, and pressure of work environment.
3. Use correct tools to disassemble/reassemble engine
4. List the steps detailing what they did and where the disassemble parts were placed.
Introduction
The lab was performed to familiarize students with basic mechanical systems as well as
introducing students to supplies needed to build and maintain engines. Participants followed
directions and learn to disassemble a simple small engine. The goal is to learn to disassemble a
simple engine to understand the intricacies of how a basic engine functions. Learning how an
engine functions at the basic level is essential to understanding how more complicated engine
functions in addition to how it can be improved.
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Description of Equipment and Materials Used
1. Flathead Screwdriver
2. 3/8 in. Socket
3. ¼ in. Socket
4. 5/16 in. Socket
5. Needle Nose Pliers
6. ½ in. Socket
7. 5/8 in. Socket
8. Ply Bar
9. 15/16 in. Socket
10. Organizing board for storing engine parts
Experimental Procedure
1. Enter Engineering technological building which has a room temperature of 23 degrees
Celsius, with a pressure of 14.7 Psi.
2. Participants began inspecting a Briggs & Stratton Model 450 series Lawn mower.
Disassembly
3. Started Disassembly at 6:20pm
4. Air filter removal
a. Using flat head screw driver remove screw on top of the air filter
b. Remove assembly.
5. Blade Engagement Cover removal
a. Remove bolt with ¼ in. Socket.
b. Remove cover.
6. Top Cover Removal
a. Remove two bolts with 3/8 in. Socket, third bolt missing.
b. Remove Cover.
7. Spark Drive Removal
a. Remove two bolts with ¼ in. Socket
b. Remove connection spring
c. Remove spark inhibitor wire connector form spark drive
d. Remove spark drive.
8. Blade and Flywheel Engagement cable removal
a. Remove the two bolts with 5/16 in. socket.
b. Remove spark inhibitor with needle nose pliers, depress the clip and pull the wire
through
c. Pull the wire through the clip, which will remove it from the engine.
d. Remove the assembly
9. Cylinder Head Removal
a. Follow the pattern to remove the bolts with a ½ in. socket
b. Successful removal of four bolts, two bolts missing.
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c. Remove the cylinder head
10. Feil Tank/Carburetor Removal
a. Two bolts holding the fuel tank were already removed, the third bolt with a ½ in.
socket. Remove spacer as you slide fuel tank assembly off of vacuum line and
intake pipe.
b. Remove governor linkage form governor arm by rotating it.
11. Blade Removal
a. Turn the engine on its side exposing the lawnmower blade. Place blade against
block, hold block in place while loosening bolt with 5/8 in socket
b. Remove the bolt, washer, blade and mandrel.
12. Removing the engine from the Mover Deck
a. Remove bolts with ½ in. socket, then rotate blade until all three bolts are
removed.
b. Remove deck of engine
c. Place the engine with the piston and valves facing upwards.
13. Crankcase Cover Removal
a. Remove 6 bolts in a certain pattern using 3/8 in. socket, last bolt missing
b. Remove cover to expose camshaft and crankshaft, use rubber mallet to bump
crankcase cover off.
14. Camshaft removal
a. Remove oil pickup wheel
b. Pull out camshaft, Valve pushrods will fall out
15. Piston Removal
a. Loosen 2 bolts holding the pistons cap to the connection rod with 5/16 in. socket.
Remove piston cap along with the bolts
b. Push free piston from the camshaft, completely remove the piston and connection
rod assembly from the cylinder.
16. Flywheel and Crankshaft Removal
a. Hold the flywheel in place with t pry bar.
b. Loosen and remove the nut on the crankshaft with a 15/16 in socket
c. Remove the flywheel guard
d. Tap the flywheel with the rubber mallet, while rotating the crankshaft, to loosen it
from the crankshaft
e. Remove the flywheel, taking notice to the flywheel key
f. Remove key from crankshaft keyway
g. Remove the crankshaft by tapping it through and remove it through the crankcase.
17. Engine disassembled at 7:16pm
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Assembly
Completed in reverse order of disassembly.
1. Crankshaft and Flywheel
a. Insert crankshaft with crankshaft key then tighten with 15/15 in socket
2. Piston
a. Coat piston cylinder and piston skirts with lubricant
b. Place piston in cylinder as far as it will go
c. Rotate the crankshaft until place where the piston connects to it is as low as
possible.
d. Tap piston back into the cylinder
e. Place the connecting rod cap around the crankshaft
f. Use the cap screws to secure the piston back to the crankshaft
3. Camshaft
a. Install valve pushrods
b. Align triangle mark on crankshaft with circle mark on camshaft
4. Oil pickup
a. Place oil pickup on camshaft
5. Crankcase Cover
a. Place cover on camshaft and crankshaft
b. Use 3/8 in socket to tighten 7 bolts to crankcase
6. Mount the engine back on the mower deck
a. Use ½ in socket to attach three bolts
7. Blade installation
a. Install mandrel, blade, oblong washer and bolt onto crankshaft.
b. Tighten blade with 5/8 in socket
8. Fuel Tank and Cylinder Head installation
a. Attach fuel tank and tighten using ½ in socket,
b. Use ½ in socket to reattach the cylinder head following the pattern in reverse
9. Blade Engagement Cable Assembly
a. Use needle nose pliers to reattach spark inhibitor wire.
b. Insert two bolts with 5/16 in socket
10. Spark Driver
a. Insert spark drive
b. Insert spark inhibitor wire
c. Insert connection spring
d. Use ¼ in socket to reattach two bolts
11. Top Cover
a. Attach Top cover
b. Use 3/8 in socket to insert three bolts
12. Blade Engagement Cover
a. Attach blade engagement cover
b. Use 1/4 in socket to insert bolt
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13. Air filter Assembly
a. Attach Air filter assembly and use flathead screwdriver to secure it
Results
The engine was disassembled in one hour-fourteen minutes. It was reassembled in nearly
half the time only taking thirty-two minutes. The small engine did not work when participant
began, while disassembling participants found a large number of screws missing and the plastic
intake tube was broken. So, in turn it would not function after it was reassembled, however after
reassembly participants found extra pieces. There were two slim plastic pieces that were not a
part of the engine assembly, they were found during the disassembly process when we turned the
mower on its side. There was also an extra screw that did not belong to the participant’s mower.
Discussion
When participants started they were curious why the mower did not function properly,
they assumed that it was disengaged for safety reasons, however, it was later explained that it
was able to function properly. However, when disassembling participants found that many parts
were missing or broken. Also lubricant was not provided however, the pieces that needed it were
slightly lubricated. Another astonishing find was that the intake tube was completely torn from
the engine and placed under the assembly with the blade.
Conclusions
Small Engines are the introduction of how an engine functions, knowing how a basic
engine function is essential to understanding and improving more complicated engines. Engines
are complicated even at their most basic level so it is important to understand each part and how
it functions in relation to the whole engine. The most important finding was that the intake tube
was torn from the assembly completely in addition to a large amount of screws and bolts
missing.
References
a. Mechanical Engineering Lab Manual by Aaron Adams & Alan Terrill
Appendences
The room temperature was 23o C, along with the room pressure being 14.7psi with an EBT of
152.
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