SA#2 Gets New Rings

 Aaron had been complaining that one of our Super As was smoking badly this past summer. It got to the point that it was becoming difficult to start and consistently showed signs of oil in the front cylinder of  the engine. We often had to pull the spark plug and clean it and warm it up a bit to get this tractor to start. So since we are not busy in winter, Aaron pulled it apart the other day.

 We sent the head out to a machine shop for new valves and guides and removed the pistons. Overall everything looked pretty good when we got inside the motor. However, when I talked to the machinist, he said the heads where in really good condition. Normally you would consider that good news, but it meant that we had not yet discovered the cause of the problem. So...

Aaron pulled the pistons and we removed the rings. In a nut shell; the pistons are that part of the motor which create the suction that draws air and fuel into the cylinder, they then compress the air and fuel mixture, and after ignition, they are thrust downward and that energy is translated to the crank shaft and from there transferred to the transmission, then the wheels. The pistons have to create a tight seal inside the cylinder walls to function correctly. To do this, each piston has a series of rings set into grooves. These rings are placed so the gap is staggered, and it is actually the tolerance of these rings relative to the cylinder wall that dictates how well this element of the system works. To test whether this relationship is within tolerance, we remove the rings from the pistons, and use the piston to place the ring in the cylinder from which it came.

 With the ring inside its cylinder, we then measure the gap between the two ends of the ring; you can see  the gap here at 9 o'clock. Tolerance? .018" Ours? .042-.048"

That's not good. We are hopeful that is wear on the rings and  that we can simply hone  the cylinder walls and replace  the rings. Once we measure the difference between the cylinder walls and the pistons themselves we can ascertain whether or not the cylinder walls are worn. If they are we will have to replace the sleeves and pistons. One nice  thing about these old tractors is that the cylinders are sleeved; which is to say that there is an iron sleeve fitted inside the cast block of the motor. If the sleeves are worn they can be removed and replaced along with a new set of pistons and rings. We will know more later.