Group 28 gate 4

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The purpose of this gate is to reassemble the engine to allow the pressure washer to be assembled completely. The process of reassembling the engine is listed below along with useful pictures and a short video of the throttle component, which was the most difficult to reassmble.

Link to main page:

Product Reassembly

Below is a step by step process on how to reassemble the pressure washer engine that was taken apart in the sections above. By maintaining the organization as suggested in the disassembly section, all major parts below should have the proper bolts, nuts, and other small parts associated with its reassembly already together. By doing this a bolt from the throttle would not be used as a fastener for the engine block and only the size tool needed is listed, not the qualities of the bolt, nut, etc.

The reassembly is broken up into 12 main sections consisting of several sub-steps. This is to provide greater organization in working with only one section of the engine at a given time, this reduces the chance of mixing up parts. Next to the section name is a number. This number represents the complexity for the overall step. This scale is similiar to that of the disassembly in that a 1 or 2 can be performed with little working knowledge of the product or the tools associated with it. For example, a 1 was given to the connecting of the starter wires at the end of the reassembly because it only requires the user to connect matching colored wires and no use of tools. A 3 or 4 may require extra steps and tools to complete the overall section and a knowledge of how to use the proper tools listed is desired. The complexity rating of 5 is left to those sections that are either very intricate or require the use of a substantial amount of tools or force. The throttle was given a 5 because it is extremely difficult to reassemble without already knowing how to do so. That is also why an image of this step is located next to it. Most of the steps do not have pictures next to them because they can be found in the disassembly step above and are still appropriate for this section as well.

Reassmbly Procedure

1) Piston Assembly(4)

a) Connect the piston to the connecting rod by inserting the piston pin
b) The connecting is rod connected to the crank shaft by two 10 mm bolts and its bottom half
i) Point: make sure the fin on the bottom part of the connecting rod faces downward

2) Cylinder head with valve assembly(3)

a) Place valves back into cylinder head
b) Place springs on top of valves
c) Put spring retainer on spring
d) Caps on top of valves
e) Rocker arm-round side down on imbedded bolts
f) Spacer nut on bolt pushed into rocker arm nut end up
g) Small hex nut placed last to hold spacer nut in place
h) Place pushrods in the two slots at the bottom of the machined surface of the engine block so that they can be actuated later by the cams
i) Align head gasket so that it will not cover any holes when placed between cylinder head and engine block
j) Slide cylinder head with valves over pushrods to be secured to the engine block
k) Four 12 mm bolts secure the head to the engine block.
l) Taking the cylinder cover place on top of the cylinder head and secure with its four 5/16” bolts.

3) Engine block(3)

a) Slide camshaft such that its main cam gear aligns with the internal gear of the crankshaft.
b) Bolt case cover to engine block using six 10 mm bolts

4) Flywheel-ignition(3)

a) The flywheel was not removed so it should be easy to locate.
b) While holding the plastic cooling fins place the roll pin cage such that the central hole is not :covered.
c) Slide these parts onto the bolt that sticks out of the flywheel
d) Using a 21mm wrench attaches the accompanying nut to the flywheel bolt over the roll pin cage and cooling fins.
e) Facing the flywheel such that the cylinder head is on the left, replace the spark plug by hand in the cylinder head.
f) Attach the ignition wiring on the outside of the engine block to the left of the flywheel and right of two visible extruding bolts. This is done with two bolts using 5/16' wrench
g) The other end of the ignition wiring gets capped onto the spark plug
h) There is a metal plate that is bolted under the cylinder head with three 5/16' bolts. Secure the plate to :a hole below the exhaust outlet and one right below the cylinder head cap. The last one is used with the pull start assembly.
i) Attach pull start assembly using four 5/16” bolts such that it aligns over the roll pin cage. One goes through the metal plate in the previous step.

5) Carburetor and Choke base(2)

a) Slide carburetor onto two extruding bolts to the right of the flywheel.
b) Slide choke base on next
c) Secure with two acorn nuts by hand

6) Throttle Assembly(5)

a) Point this requires looking at the adjacent picture for clarification
b) There are two larger metal pieces. The one on the left in the image is to be attached first.
c) The cotter pin is pushed into a groove on a small black rod that comes out of the engine block :top.
d) Above this pin rests the more slender portion of the throttle.
e) A t-bolt is slid horizontally through that part of the throttle and is held in place by a flange hex nut.
f) The larger portion is bolted to the block and to the cylinder head (next to the spark plug) with two 5/16’’ bolts.
g) A metal rod attaches from the piece on the right to a small black piece on the carburetor
h) The smaller spring attaches in the same manner and can be seen more clearly in the pictures.

A useful video clip of the throttle can be found here:

7) Gas tank(2)

a) The carburetor has a tube which can be thread into the bottom of the gas tank
b) After threading the tube in, the engine can be placed on top of the engine as seen in the picture.
c) The tank has two bolt threads already on it that are secured to the tank with two 10 mm nuts. A bolt (8 mm) on the opposite side next to the throttle completes this step.

8) Exhaust(3)

a) With the exhaust is a gasket that slides over the two bolt threads extruding from the exhaust.
b) The actual exhaust assembly is slid over these bolt threads and secured with two hex nuts (1/2”)

9) Air Intake(2)

a) Secure base of air intake above carburetor using the button and flat head screws
b) Next place air filter over base. Secure with wing nut.
c) Place cover over the filter and secure with another wing nut.

10) Engine to frame(3)

a) Align engine such that the four holes on the base line of with the holes on the frame.
b) Secure by putting four 1/2” bolts through the engine into the frame with four 10 mm bolts securing the :bolts in place

11) Fuel pump(2)

a) Attach the fuel pump to the base of the pressure washer two 8 mm bolts
b) Attach single end hose line to open port in gas tank
c) Attach double end hose line to hole in carburetor and the other hole it lines up with.

12) Finish connecting loose wires by the on/off switch, matching colored wire together.(1)


The piston must be oriented correctly to be reassembled within the cylinder. The problem with the piston is that it has four ways that it can be put into the cylinder, only one of which is the correct way. The correct way is to place the piston and connecting rod base in the cylinder, such that the base’s fin and overall piston is angled downward, toward the bottom of the engine block. The group assessed the positioning of the crankshaft and gears within the block and decided this was the only possible method that would insure proper function of the engine.

The throttle provided much difficulty when reassembling. This was because of the various small components such as the springs and connecting rods that held it together had several possible arrangements. The group closely analyzed the design of the throttle and with the aid from a picture from disassembly, was able to properly reassemble the throttle.

A few comments about the engine after disassembly are made below.

Due to rules and regulations on campus group 28 was not able to see if the pressure washer ran prior to being taken apart or afterward. Based on evidence found inside the engine it was clear that it had been taken apart before and most likely was not reassembled correctly in order for it to run correctly. The evidence included several incorrect fasteners (wood screws where bolts should be) and a misalignment of an internal gear that the group managed to straighten. The timing of the camshaft and valves would have needed to been noted before taking everything apart so it could go back together the same way as before. Since group 28 had no way of knowing if the timing was right when they took it apart they could not know if the timing was put back to manufacture standards. Group 28 was able to successfully reassemble the engine in slightly better condition than it was found to complete the project.

The reassembly process followed the same steps as the disassembly process in reverse order. The same tools were used to perform both assembly and disassembly which included mostly the use of a socket wrench and a socket set (both SAE and metric). Group 28 was able to get the engine fully assembled back to how it was given to them with minor corrections made.

Based upon the dissection of this gasoline engine, group 28 determined that it uses a proven design which has been used in many similar products. Thus there are no additional recommendations to improve the design or function of this product other than what can be found in the design revision section of this wiki page.