1989 Blaster Engine Rebuild - Part 3, Two-Stroke Software Review

1989 Blaster Engine Rebuild - Part 3

Part 1 - Part 2 - Part 3 - Part 4 - Part 5 - Part 6 - Part 7 - Part 8 - Part 9 - Part 10 - Part 11 - Part 12 - Part 13 - Part 14

Damage & Discrepancies

Two-Stroke Software Review

Part 1

Damage & Discrepancies
When the crankshaft stopped turning it did so because it hit against the inside of the engine case. There is plenty of material in this area for normal use and circumstances, but the case protested when it was faced with having a rod end scrape against it at high rpm.

This half of the engine case shows where the rod spent its last revolution - with that rod anyway.

When I looked closer I found small bits of hard metal embedded into the aluminum. It must have come from the bearing cage.

One case half is attached to the barrel here to check the fit. I noticed the amount of alignment correction that's needed - in this case that amount is about 1 mm. I scribed a line using a sharp carbide tipped scribe and I used the case half as the template to draw against. When it's disassembled the line is easy to see and to cut to. I assembled the other half and found a similar amount of discrepancy. There is also some mismatch at the edges of the cylinder liner where it aligns with the aluminum case.

The piston is installed on the rod in order to discover and record the port timing. I found it of particular interest that when the piston is located at BCD, it is still covering a little over a millimeter of the transfer port windows. Additionally the exhaust port was covered by the piston about 1/2 of that amount. I think it would be wise to raise this barrel if I was going to raise all of the ports for increased power. It seems as if it was designed that way in order to later be taken advantage of... Hmmm.

To Lap

I looked up this word in my electronic dictionary to help me better explain its meaning. It turns out there are a bunch of uses for the word. I found everything from it being the abbreviation for leukocyte alkaline phosphatase to it being one circuit of a racetrack. I also found one reference to it being used to describe a rotating disk for polishing a gem or metal - that's in the ball park. I'm sure I could investigate it further to make it more clear but I'm not going to. I am talking about taking a known flat surface, such as a granite slab or a flat piece of glass and use its surface to attach some sort of abrasive media to. When the other part (the one that is not flat) comes in contact with the flat one and its abrasive, little by little its high spots will be worn down and it will gradually become more flat. There are varying degrees of flat but for the purpose of this rebuild I am using a 2" thick granite plate that is 14 inches square. It is defined as being tool room grade. Speaking plainly, that means it's really flat, not the flattest thing on the planet, but it will do just fine for the purpose of making small parts for two stroke engines flat. I have been using this plate for quite a number of years and I often take it with my tools when I take a long off road riding vacation. Generally I attach either wet-dry sand paper to it or I'll cover it with a piece of 1/4" to 3/8" thick glass and use an abrasive medium such as valve lapping compound to supply the cutting ability. Usually glass is used for finishing the surface after it has been lapped with varying degrees of sand paper, or for parts that are very flat to begin with. I would never lap anything directly against it (without something between it and the part). Sometimes I use the surface plate to check the flatness of parts. It's easy to spot a rocking or wobbling part - sometimes it's easy to see daylight between the plate and the part. In cases where that happens the part is not flat. When surfaces are flat, they show no light between them. Sometimes when two very flat surfaces come into contact with each other they react to the column of air that's stuck between them. This can be observed when putting a piece of glass on the top of the granite slab. The air in between the 2 parts cannot squeeze out directly so it forces the parts to shift laterally, either to the left or to the right. Eventually the two parts will come very close to each other. Also, when separating two flat surfaces it is sometimes difficult to pull them straight away. Often it is necessary to slide them apart, off to the side. Suction can develop between the two surfaces enough that it is virtually impossible to pull them directly away. It is this phenomenon that keeps things like contact lenses attached to eyes. It is referred to as fluid attraction. It is a powerful natural occurrence that follows the laws of science. In some cases we depend on it to continue doing what it seems to want to do the best - either stay together or stay apart, but not hurry between extremes of either condition. Even while lapping engine cases the attraction between the flat surfaces is very strong. With just a thin rib of metal defining the engines crankcase and transmission, as it starts to become as flat as the surface plate or the glass it grabs the surface real hard and does not seem to want to let go. With the engine cases it is necessary to lightly pull off one side before the other because it'll not likely come apart when pulled straight up.
Short Story
Some time ago I went on a riding trip without the slab and though it's almost never needed I needed it real bad. The little LT50 wouldn't start. After fiddling with it for a couple of minutes I found out that when I pulled the starter cord I was getting blasted by a small gust of air. The head gasket had been replaced before the trip but the flatness of the head had not been checked - the head was warped. At Glamis there are no machine shops around. I knew that if I had my slab I could attach some sand paper to it and rub the small aluminum head against it until it was flat, but I didn't have it. Sitting in my motor home I was surrounded by all kinds of flat glass windows so I was trying to determine if I could remove one to use as a flat surface. When I glanced at the oven I immediately noticed the hinged door with a thick glass window in it. I removed the door and placed it on the table. I cleaned it real well and attached a piece of emery cloth to it using masking tape. I rotated the little head in a figure eight pattern while pressing it very lightly against the glass door lapping plate. I used WD-40 to lubricate it and to help clear the metal particles. After a few minutes the surface started to become flat. I could witness this by removing the head from the plate, cleaning it off and taking notice of where the material was being removed from. When doing this type of operation it is easy to tell a freshly cut, polished-smooth new surface from an old pitted and dark warped one. After a few minutes I had achieved success - the head was flat. When I removed the emery cloth from the door and cleaned both the head and the glass I placed the parts against each other. I was trying to see or tell if I could rock the head either front to back or side to side. I couldn't. It was flat. I put the head back on the little LT and off it went with small kids grinning from ear to ear. It still has the top assembled from that day.

This small slab works well for lapping small parts. Either glass or sand paper will work with it. If using glass it needs an abrasive. The plate has to be very clean before attaching anything to it or it may not work well enough. Any surface that has machine marks on it can be made clear of imperfections with some time and effort.

A piece of 600 grit wet-dry paper is attached to it with 2" wide masking tape. WD-40 supplies the lubrication. It can take a great deal of time to make a surface flat. Usually 90% of the surface will get flat within the first 10% of the time spent. Ninety percent of the time will be spent on getting the last few percent of the surface as flat as the rest.

I attached two pieces of 1500 grit paper to the slab to "rough in" the cases. I finished them by lapping them against a 1/4" thick piece of plate glass attached to it. I used 'Clover Fine' lapping compound as the abrasive.

This is the way the stock Blaster head looks. I know this design will run the engine, but when looking for more power we will need to improve upon it. This will be one area that 2 stroke software will come in very handy.

1989 Blaster Engine Rebuild - Part 3

Part 1 - Part 2 - Part 3 - Part 4 - Part 5 - Part 6 - Part 7 - Part 8 - Part 9 - Part 10 - Part 11 - Part 12 - Part 13 - Part 14

Damage & Discrepancies

Two-Stroke Software Review

Part 1

Damage & Discrepancies When the crankshaft stopped turning it did so because it hit against the inside of the engine case. There is plenty of material in this area for normal use and circumstances, but the case protested when it was faced with having a rod end scrape against it at high rpm.
This half of the engine case shows where the rod spent its last revolution - with that rod anyway.	When I looked closer I found small bits of hard metal embedded into the aluminum. It must have come from the bearing cage.
One case half is attached to the barrel here to check the fit. I noticed the amount of alignment correction that's needed - in this case that amount is about 1 mm. I scribed a line using a sharp carbide tipped scribe and I used the case half as the template to draw against. When it's disassembled the line is easy to see and to cut to. I assembled the other half and found a similar amount of discrepancy. There is also some mismatch at the edges of the cylinder liner where it aligns with the aluminum case.	The piston is installed on the rod in order to discover and record the port timing. I found it of particular interest that when the piston is located at BCD, it is still covering a little over a millimeter of the transfer port windows. Additionally the exhaust port was covered by the piston about 1/2 of that amount. I think it would be wise to raise this barrel if I was going to raise all of the ports for increased power. It seems as if it was designed that way in order to later be taken advantage of... Hmmm.
To Lap I looked up this word in my electronic dictionary to help me better explain its meaning. It turns out there are a bunch of uses for the word. I found everything from it being the abbreviation for leukocyte alkaline phosphatase to it being one circuit of a racetrack. I also found one reference to it being used to describe a rotating disk for polishing a gem or metal - that's in the ball park. I'm sure I could investigate it further to make it more clear but I'm not going to. I am talking about taking a known flat surface, such as a granite slab or a flat piece of glass and use its surface to attach some sort of abrasive media to. When the other part (the one that is not flat) comes in contact with the flat one and its abrasive, little by little its high spots will be worn down and it will gradually become more flat. There are varying degrees of flat but for the purpose of this rebuild I am using a 2" thick granite plate that is 14 inches square. It is defined as being tool room grade. Speaking plainly, that means it's really flat, not the flattest thing on the planet, but it will do just fine for the purpose of making small parts for two stroke engines flat. I have been using this plate for quite a number of years and I often take it with my tools when I take a long off road riding vacation. Generally I attach either wet-dry sand paper to it or I'll cover it with a piece of 1/4" to 3/8" thick glass and use an abrasive medium such as valve lapping compound to supply the cutting ability. Usually glass is used for finishing the surface after it has been lapped with varying degrees of sand paper, or for parts that are very flat to begin with. I would never lap anything directly against it (without something between it and the part). Sometimes I use the surface plate to check the flatness of parts. It's easy to spot a rocking or wobbling part - sometimes it's easy to see daylight between the plate and the part. In cases where that happens the part is not flat. When surfaces are flat, they show no light between them. Sometimes when two very flat surfaces come into contact with each other they react to the column of air that's stuck between them. This can be observed when putting a piece of glass on the top of the granite slab. The air in between the 2 parts cannot squeeze out directly so it forces the parts to shift laterally, either to the left or to the right. Eventually the two parts will come very close to each other. Also, when separating two flat surfaces it is sometimes difficult to pull them straight away. Often it is necessary to slide them apart, off to the side. Suction can develop between the two surfaces enough that it is virtually impossible to pull them directly away. It is this phenomenon that keeps things like contact lenses attached to eyes. It is referred to as fluid attraction. It is a powerful natural occurrence that follows the laws of science. In some cases we depend on it to continue doing what it seems to want to do the best - either stay together or stay apart, but not hurry between extremes of either condition. Even while lapping engine cases the attraction between the flat surfaces is very strong. With just a thin rib of metal defining the engines crankcase and transmission, as it starts to become as flat as the surface plate or the glass it grabs the surface real hard and does not seem to want to let go. With the engine cases it is necessary to lightly pull off one side before the other because it'll not likely come apart when pulled straight up. Short Story Some time ago I went on a riding trip without the slab and though it's almost never needed I needed it real bad. The little LT50 wouldn't start. After fiddling with it for a couple of minutes I found out that when I pulled the starter cord I was getting blasted by a small gust of air. The head gasket had been replaced before the trip but the flatness of the head had not been checked - the head was warped. At Glamis there are no machine shops around. I knew that if I had my slab I could attach some sand paper to it and rub the small aluminum head against it until it was flat, but I didn't have it. Sitting in my motor home I was surrounded by all kinds of flat glass windows so I was trying to determine if I could remove one to use as a flat surface. When I glanced at the oven I immediately noticed the hinged door with a thick glass window in it. I removed the door and placed it on the table. I cleaned it real well and attached a piece of emery cloth to it using masking tape. I rotated the little head in a figure eight pattern while pressing it very lightly against the glass door lapping plate. I used WD-40 to lubricate it and to help clear the metal particles. After a few minutes the surface started to become flat. I could witness this by removing the head from the plate, cleaning it off and taking notice of where the material was being removed from. When doing this type of operation it is easy to tell a freshly cut, polished-smooth new surface from an old pitted and dark warped one. After a few minutes I had achieved success - the head was flat. When I removed the emery cloth from the door and cleaned both the head and the glass I placed the parts against each other. I was trying to see or tell if I could rock the head either front to back or side to side. I couldn't. It was flat. I put the head back on the little LT and off it went with small kids grinning from ear to ear. It still has the top assembled from that day.
This small slab works well for lapping small parts. Either glass or sand paper will work with it. If using glass it needs an abrasive. The plate has to be very clean before attaching anything to it or it may not work well enough. Any surface that has machine marks on it can be made clear of imperfections with some time and effort.	A piece of 600 grit wet-dry paper is attached to it with 2" wide masking tape. WD-40 supplies the lubrication. It can take a great deal of time to make a surface flat. Usually 90% of the surface will get flat within the first 10% of the time spent. Ninety percent of the time will be spent on getting the last few percent of the surface as flat as the rest.
I attached two pieces of 1500 grit paper to the slab to "rough in" the cases. I finished them by lapping them against a 1/4" thick piece of plate glass attached to it. I used 'Clover Fine' lapping compound as the abrasive.	This is the way the stock Blaster head looks. I know this design will run the engine, but when looking for more power we will need to improve upon it. This will be one area that 2 stroke software will come in very handy.