Group 36 Disassembly Process

Friday May 24 2013 14:44

Introduction

This is the preliminary design review for Group 36. This gate includes causes for corrective action as well as the dissection process. The causes for corrective action discusses any changes that needed to be made to the management and work proposals. The dissection process is a step-by-step instruction of how the group disassembled the dirt bike engine and transmission.

Directory

Home: Group 36 Home Page

Gate 1: Request for Proposal

Gate 3: Coordination Review

Gate 4: Critical Design Review

Group 37: Project

Product Dis-Assembly

Causes for Corrective Action

Group 36’s preliminary Project review is to dissect the transmission and engine of a dirt bike. So far the execution is going as planned. All four of the active group members met at the laboratory on the 19th of October and the product was disassembled. As planned, Dan Cocciardi, the group leader, took a visual (both pictures and video) documentation of the whole process as John Flight, the Technical expert, with the aid of Nnamaka Nwufoh took the systems apart. He went step by step, in a chronological order. Eric Dane, the Data Acquisitions coordinator, took a proper written documentation of the process, recording all tools used, every step taken. Nnamaka then bagged and tagged all parts and hardware accordingly. The dissection process was considerably easy, but, it required proper written and visual documentation which took up the most time. The labeling and organization of the parts will greatly expedite the Critical project review stage. The general coordination of the whole process was admirable. Everybody already had their area of concentration, but did not hesitate to help out wherever it was required. All the teammates of group #36 are at different levels of their academic pursuits, and therefore, different schedules. So, sometimes, getting an all-round schedule that suits everybody might not be feasible. But, due to the commitment the teammates have to outstanding workmanship, they always resolve the situation. The next time the group will meet will be the 1st of November, 2009 to discuss the next step, Coordination Review of the project.

Management Proposal Overview

This seemed to work out very well. We got the dis-assembly done during the planned times. Individuals did their jobs with competence and in a timely manner. The work load seems to have been distributed fairly.

Review of initial dissection assessment

Basic

• a metric socket set will be needed, starting from a 6mm and going up to a 21 mm.
  • This was correct. All socket wrenches that were needed fell within this range.
• a 3/8 ratchet and various sizes of extensions will be needed, starting with a #1 and going up to a #4 just in case some prying becomes necessary.
  • This proved to be correct. However, it did not go far enough. We needed several other ratchet sizes. We also initially assumed that bolts on the motor would be in Customary Units because bolts attaching the motor assembly to the bike were as such. It turned out that all bolts on the motor were metric. This was easily remedied as all the necessary tools were available. Had they not been, it would have been a considerable set back. We should have prepared for this in advanced.
• a box end wrench set will also be needed in the same sizes of the socket set.
  • This was correct and we had these tools available to us.

Engine and transmission systems

• a piston-spring compressor
  • We used a screw driver in the place of this, it proved to be easy enough and sufficient.
• a leather-skin mallet and a bearing press to remove and reinstall the pressed-in bearing.
  • This step was never undertaken because it was deemed unnecessary.
  • We stopped disassembling the motor/transmission housing once we got into the transmission and could see it inner workings. This also proved to be true about the clutch and carburetor. We got the motor taken apart to a point where we could tell what was going. In regards to the centrifugal clutch and carburetor, it was decided to use reference material to explain their inner workings because we were unsure if we could get these parts back together should we take them apart.

Misc

• a drain pan for the oil inside the motor
  • Proved to be a major problem. We assumed there would be one available in the lab; there was not. We ended up using a paper cup and a plastic bottle and a entire roll of paper towels. The lack of this basic equipment proved to be a major annoyance throughout the project. If this project did anything in reinforced the basic premise of assume nothing. The simplest things can be the biggest problems.
• a chain breaker, in order to remove the engine and transmission from the chassis of the dirt bike.
  • Proved unnecessary. There was a master link that was removed with a Phillip's head screw driver.

The complete dis-assembly of the dirt bike should take between 2 to 3 hours, in a non-crowded area with full tool availability.

• This proved to be spot on. It took us almost exactly three hours to get the bike taken apart.

Unforeseen issues

• There was far more oil in the motor than we suspected. We did not plan to let it drain and, as a result, did not let it drain long enough. This made the entire process more complicated then necessary. The main issue was with our own grip - motor oil found its way onto our hands and made gripping objects a hassle. We had to constantly clean our hands off.
• Keeping the motor still. There was no vice of any kind we could use to clamp the motor down. This led to precarious situations like someone climbing up onto the table and putting there full body weight on the motor so it would not move when considerable torque needed to be applied.
• Not knowing the layout of the motor. Without access to any sort of schematic of the system, taking the motor apart involved more consideration than thought. Several times we reached a point in the dis-assembly where we did not know how to continue. Specifically:
  • Getting the magneto off. We could not get enough torque on the center bolt holding it in because it (the magneto) spun freely. Several attempts at stopping its rotation by wedging screw drivers into various locations proved ineffective. The best method eventually involved locking pliers, a screw driver and a ratchet. Had a large vice been available, to hold the motor still, many things, including this, would have been easier.
  • Under the magneto there was a round metal plate that allowed access to the transmission and the sprocket that delivered power to the cam shaft. Getting this off required a #3 screw driver. We had planned to need one. We did not have one in the lab. As such we tried to get it off with a #2 and this proved to be foolish. We eventually found a single #3 screw bit in the lab tools and the TA had the 1/4 drive ratchet in his car we needed to use it. Without that ratchet and that bit the project would have ground to a halt (it took an extra 30 minute fr this anyway.)
  • Getting the cam shaft and piston housing off required the removal of the chain attached to the sprocket described immediately above. We did not know how to get to this so we considered taking the clutch off. This proved to be very difficult, ran the danger of destroying important gears, and worried us about our ability to reassemble the clutch; we did not want to remove the clutch or take it apart.
• Our inability to get the magneto off (as described above) led us on a trial and error journey of deciding how to get one side off (clutch or magneto) so we could access the transmission housing and get the cam shaft chain detached. This proved to be the biggest problem of the dis-assembly. The combination of our ignorance, the lack of a few basic tools we knew we would probably need, the presence of oil on many parts, the lack of a vice to keep the motor from jostling around, and a lack of patience made the process take longer than it needed to.
• We arrived at the end of our dis-assembly with a single mystery bolt. As of right now, we are not sure where it went. A momentary lapse in our cataloging procedure caused this and may prove to be of considerable irritation during re-assembly.
• Final note - We never foresaw the issue of space and the problem of sharing tools. When we went in to do our dis-assembly, so did five or six other groups. This led to a rationing of tools and space to work. This simply cost more time and effort, as you sometimes had to scour the room for the ratchet or rubber mallet you had a minute ago but now was in the hands of someone else across the room. Further, some people who had already done there dis-assembly were simply inconsiderate. They left there broken down system strewn across one of the four desks in the entire room. When 37 groups are sharing the space, taking up 1/4 of the work space is simply wrong; some people did not even think of this. As such, time was needed to move other group projects, sometime piece by piece, to some place where it could be stored with some degree of order. In our immediate experience, a group left bags of parts, free parts, plastic bags, and tape across a table with no sense of order or concern for the space. This was unforeseen and took up our time.
• All issues with the dis-assembly were overcome. The process is described below in the Dissection Procedure

Dissection Procedure

Overview

Figure: Magneto and Output Sprocket Cover

Figure: Head

Figure: Clutch Side Cover

Each step will have a difficulty rating from 1 to 5. A rating of 1 corresponds to a simple task requiring minimal effort, while a rating of 5 corresponds to a task that will require a large amount of effort, several attempts, or assistance from another person.

• For the required tools section:
  • A wrench refers to a ratcheting socket wrench. Socket wrenches are recommended for most of the bolts on the engine and transmission.
  • A standard open ended wrench may be used on some bolts if preferred, but they will not be useful for most of the bolts. The instructions will explicitly state when an open ended wrench is recommended.
• All bolts used on this product are hexagonal.
• All bolts should be put into bags and labeled by what part they came from so to not cause confusion during reassembly. Labeling parts with tags or masking tape is also recommended.

Step 1: Drain Oil

Tool(s): 17 mm wrench, drain pan

• Difficulty: 1
• Dis-assembly Process

a. There are several 17mm bolts on the underside of the engine. Remove the bolt on the side closest to the clutch and allow the oil to drain into a container. Allow the oil to drain for 15-20 minutes. There will still be oil on the internal components so paper towels or rags will be beneficial later on for drying off some of the components.

Step 2: Remove Clutch Cover

Figure: Clutch Cover Removed

See: Figure: Clutch Cover Removed

Tool(s): 8 mm wrench

• Difficulty: 1
• Dis-assembly Process

a. There is a metal cover over the clutch mechanism on the engine. Unscrew the two bolts holding it in place, then pull off the cover.

Step 3: Remove Cam Shaft Cover

Figure: Cam Shaft

See: Figure: Cam Shaft

Tool(s): 8 mm, 9 mm, 10 mm, and a 17mm wrench, vise, (rubber mallet and open ended wrench are optional)

• Difficulty: 4
• Dis-assembly Process

a. The cam shaft case is the long black ribbed section between the head and the transmission block. On top of the head there is a plate with four bolts and washers at each corner. Remove the bolts and washers and slide off the cover section. Then remove the gasket.

b. On the side opposite the clutch there is another square metal cover panel. There is a round metallic cover directly opposite this panel. There are three bolts fastening the square panel to the cam shaft case, two 8 mm bolts and one 10 mm bolt. Remove the two 8 mm bolts first than the 10 mm bolt. The 10 mm bolt is long and extends all the way through the cam shaft case. Once all these are removed pull off the circular cover mentioned earlier.

c. There are two more circular covers, one on top and bottom of the cam shaft case. These however have a 17 mm bolt head in their center. These two covers require more force to loosen than the previous bolts so a vise or additional person will be needed to hold the engine steady. A rubber mallet can be used to strike an open ended wrench attached to the bolt as another method to loosen.

d. Underneath the metallic disk is a nut on a screw. Use a 9 mm wrench to remove the nut. This must be done for the top and bottom openings

Step 4: Remove Spark Plug

Figure: Spark Plug

See: Figure: Spark Plug

Tool(s): 16 mm wrench

• Difficulty: 1
• Dis-assembly Process

a. The spark plug is long so a deep socket will be required. The socket must be long enough to fit the spark plug and reach the bolt at the bottom, (at least 2.5 inches.)

Step 5: Remove Magneto Side Transmission Housing

Figure: Magneto Cover

See: Figure: Magneto Cover

Tool(s): 8 mm wrench, Flathead screwdriver

• Difficulty: 3
• Dis-assembly Process

a. On the opposite side of the clutch there is another cover protecting the magneto and transmission output sprocket. There are 10, 8 mm bolts surrounding the perimeter of the casing. Loosen and remove each of these screws.

b. Once the screws are removed the section of casing must be pried off. A Flathead screwdriver is recommended or some other tool that can be used to get into the space between case sections to obtain some leverage. There is a gasket that must also be taken off after the casing is removed.

Step 6: Remove Kick Start and Selection Lever

Figure: Selection Lever

See: Figure: Selection Lever

Tool(s): 10 mm wrench, Flathead screwdriver

• Difficulty: 3
• Dis-assembly Process

a. The selection lever is on the clutch side of the engine (the lever that changes gears). There is one 10 mm blot that must be removed then the lever slides off.

b. Once the selection lever has been removed the selection linkage will slide off.

c. A 10 mm bolt must be removed on the kick start (located on the opposite side as the selection lever). There is a tighter fit with the kick start so the Flathead screw driver will be needed to help pry the kick start loose so that it can be removed.

Step 7: Remove Sprocket

Figure: Sprocket and Magneto

See: Figure: Sprocket and Magneto

Tool(s): 10 mm wrench

• Difficulty: 1
• Dis-assembly Process

a. There are two bolts holding the sprocket (output shaft of transmission) to the transmission. Remove the bolts, slide off the sproket, and remove the gasket.

Step 8: Remove Magneto

Figure: Magneto & Sprocket Removed

See: Figure: Magneto & Sprocket Removed

Tool(s): 10 mm and 14 mm wrench, Phillip head screwdriver, Flathead screwdriver, rubber mallet, locking pliers, ¼ in drive ratchet, #3 screw head

• Difficulty: 5
• Dis-assembly Process

a. There are two phillip’s screws and a 14 mm bolt holding the magneto in place (the magneto is the circular component that is on the side opposite the clutch). Remove the two screws first.

b. To remove the 14 mm bolt the round clutch mechanism on the other side must held to prevent it from rotating. Have another person clamp down on the mechanism with the locking pliers to hold it in place. Once this is done try loosening the bolt. It may also be useful to clamp down the entire motor to stop any addition rotation. Remove the bolt once it is unscrewed.

c. Pry the magneto off once all the screws and bolts are removed. A flathead screwdriver can give some additional leverage and a rubber mallet can be used to apply additional force.

d. Underneath the magneto is a wire coil held in place by two additional phillip’s head screws. Unscrew these two screws.

e. There is also wiring under the magneto. There are two clips around the wiring, which are spot welded to the transmission case. Use the flathead screwdriver and rubber mallet as a hammer and chisel to break the welds.

f. There is a metal plate with two more phillip’s head screws on this side of the motor. Use the #3 screw head and ¼ in drive ratchet to remove these screws. Make sure to use these specific tools because they create a tight fit and allow for enough force to remove the screws without stripping them.

g. In the middle of these two screws is a bolt. Remove it with a 10 mm wrench. Once this is done the metal plate they were holding in place can be removed.

Step 9: Remove 17 mm bolt

Tool(s): 17 mm wrench

• Difficulty: 3
• Dis-assembly Process

a. In the first step a bolt was removed to drain the oil. Go back to this region of the motor and there should still be another bolt on the opposite side of the motor from Step 1. Under this bolt is a spring. The bolt must be loosened and pressure must be applied to it as it slides out so that the spring does not shoot out of the hole. Once the spring is no longer compressed the bold and spring can be taken out.

Step 10: Remove Tensioner

Figure: Tensioner

Tool(s): 17 mm wrench, rag

• Difficulty: 2
• Dis-assembly Process

a. There is a single black bolt on the inside of the transmission. Use a 17 mm wrench to remove it.

b. If you follow the bolt hole from Step 10 to the inside of the transmission you should find a metal rod. This is the tensioner. Slide the tensioner up through the Step 10 bolt hole. There will most likely be oil in the bolt hole that will come out as the tensioner is slid up. Use the rag to wipe up the oil as it spills out.

Step 11: Remove Valve Assembly

Figure: Camshaft Sprocket

Tool(s): 8 mm wrench, screwdriver

• Difficulty: 4
• Dis-assembly Process

a. During Step 3 there was a circular metallic cover that was removed and underneath there was a chain attached to a gear. Go back to this area and remove the three bolts around the center of the gear with an 8 mm wrench.

b. Once the bolts are removed the chain around the gear must be taken off to remove the gear. This part can be difficult since there is little room to move the gear and chain around. Use a screwdriver for assistance and keep shifting the gear and chain around until they separate then remove the gear.

c. The chain connects to another gear inside the transmission body. Take the chain off this gear and pull it the cam shaft casing and out the transmission.

d. Now that the chain has been removed the head can be removed.

e. The black sleeve below the head can now be removed, along with the piston head contained inside. This exposes the cam shaft.

Step 12: Remove Piston Head

Figure: Crankshaft

Tool(s): x2 Flathead screwdriver (or pliers)

• Difficulty: 2
• Dis-assembly Process

a. There is a pin connecting the piston head to the rod. Remove it by prying it apart with the two screwdriver (or with small pliers, pry them apart.)

b. Remove pin by hand. (Will slide out easily)

c. Remove piston head.

Step 13: Split Inner Transmission Case

Tool(s): 8 mm wrench, rag

• Difficulty: 1
• Dis-assembly Process

a. There are seven more bolts around the perimeter of the transmission case. Loosen and remove all of these with the 8 mm wrench.

b. Pry open the transmission case using the Flathead screwdriver in the same manner as mentioned in Step 6.

c. Slide off the central section of the transmission case.

Figure: Inside Transmission

Figure: Split Transmission Case

Final Assessment

This product appears to be made to be taken apart relatively easily. There were some challenging parts to loosen some nuts, but the overall process was very manageable. All the bolts where either hexagonal or Phillips head, which are the more common bolts that people would have tools to work with. We were also able to completely disassemble the engine and transmission in 3 hours. It took half that the get to the parts of the engine that would most like require maintenance (i.e. magneto stator plate, drive sprocket).

The only fasteners used were bolts and these were only Phillips head and hexagonal head bolts. These were probably used because Phillips screwdrivers and hexagonal socket wrenches are common in most households. However the hex head bolts were in metric dimensions, which is probably a sign that the product is sold and/or produced in other countries.

Special tools were not required during the disassembly process. This also goes along with the idea that the product was meant to be taken apart easily.