Job-specific blog Post

Assignment

Part 1:

The first thing that I did to the Yamaha SX 650 was remove the engine from the bike frame. This was done by removing the drive chain which attached the drive gear inside the engine to the rear wheel. Next we removed bolts securing the engine to the frame alone with removing the electrical components. Because the bike is a kick start there wasn’t as many electrical components it was mainly the ignition advance. Once the engine was removed from the frame I removed the carburetors from the engine. Because the bike sat for so long outside the carburetors will have to be cleaned. I then began to remove the top end oil tube, valve cover and cylinder head. We did this because when we used the kick starter to try to start the bike it wouldn’t move leading us to the assumption that one or both of the cylinders were seized. The cylinder head was removed by taking the bolts off, the ignition advance and removed the cam shaft and chain. We did not have a chain breaker to remove the chain but we used the cam chain tensioner to release as much slack as we could so we would be able to slide the camshaft out of the engine. Once we got the piston free we sent the cylinder and cylinder head to a machine shop where they performed a process called Deglazing. This process was basically a big oven that burnt all the years of rust and grime off the components. I then spent time cleaning the grooves where the piston rings had been because the seized piston had resulted in seized piston rings and lots of built up grime. I then took the side covers off to inspect the rest of the engine. It was apparent that the previous owner had taken very good care of the bike because the inside of the engine was very clean as a result of regular oil changes. Upon further inspection of the oil filters we noticed that there was an abundance of black flakes of plastic and metal. This was a result of the cam chain guide needing to be replaced.  

Here you can see the removal of the seized piston and cylinder.

Part 2:

1: The seized piston was a major concern. It took a lot of sanding and cleaning to get it back to the way it should be. Wellst trying to remove the stuck piston rings we made some imperfection is the cylinder making us wonder if this would affect the performance during the compression, luckily the machinist said that the new piston rings should make up for those small imperfections.        

Here you can see the piston ring gaps being chiseled out.

2: The cylinder block was another major concern. The carefully machined walls of the cylinder were coated with grime and rust begging the question of how to clean and repair them without damaging them. After some research we found that the local machine shop can perform a process called “Deglazing”. The Deglazing process is basically a big oven that bakes the grime and rust at such a high temperature that it falls off leaving the perfectly machined surface.

3: Since the bike has sat for so many years exposed to the elements it is safe to assume that the carburetors are filthy. We will have to look into whether or not the disassembly is something we can do at school or something we will have to pay someone to do. Either way the two carburetors are a crucial part of the engine and will need to be cleaned and rebuilt.