I guess I don't understand why one would stay away from full throttle. Is there something behind this, or is it just an OWT (Old Wife's Tale)?
Yeah, I know the Kubota manual says so too, but it seems quite ambiguous to me. They say the parts aren't used to each other, like surface inches per second will make some big difference. They don't say anything about percent load on the tractor. Now that will get some parts used to each other quick. Keeping the RPMs down will limit the power output, but under load you will still get a pretty big torque rise from the governor.
I guess what I would like to achieve in my break-in would be good ring seating. I don't know how to do this with confidence on a tractor.
On typical engines the cylinders are cross hatch honed so that in the first few hours the additional friction mates the two surfaces in a highly polished manner. If you get glazing (hardening of the high points) on the cylinder walls, you will not achieve optimum compression and will have additional oil blow by. The only way to fix this is to replace the rings and rehone the cylinders. This is not a catastrophic event for a tractor. Fairly subtle I would think. The factory says the engine has been tested. Does anyone know if the factory does any break in of the engine? Maybe they take care of this in a controlled environment. That would be nice.
The only reason I can think of for keeping the RPMs down would be to cause a high manifold pressure (relative 0 for automotive folks) under load. This causes the rings to apply additional pressure on the cylinder walls and helps the initial surface mating process. However, you would need a continuous load.
If I had my choice, I would like to break-in my tractor in by dropping a plow for about 10 hrs or so with engine power between 65-75 percent and make sure my engine temperature behaved properly.
I assume varying RPMs is get a good distribution on the top ring groove wear. This would imply that there is a lot of vertical movement in the bearings. I am just not sure this is the case or buys very much. As the governor adjusts under varying loads, the associated inertia would do the same thing (if it is an issue at all).
I thought I would throw this out. Looks like a great opportunity to learn something from a bunch of smart folks... /forums/images/graemlins/cool.gif
