The 282 in the 656 Hydrostatic drive uses a speed advance system. The very early gear drive 656 also used that speed advance. We only sold one 656 gear drive that had speed advance. I believe there may be a few mixed in with speed advance before all gear drive 656 were load advance. The difference is that a speed advance pump has no automatic advance at low speeds and gradually starts to advance the injection timing as the engine speed increases. It maintains that advance at all loads unless speed of engine decreases sufficiently to reduce advance. The load advance works differently and to me gives a smoother running engine under load but may rattle more under no load. The load advance gives full advance as soon as the engine is running. It maintains that full advance at low and high speeds under no load. As you come under a load it retards injection. Now, the reason they used the load advance, which by the way is what all 4 & 560's had, is that in a Roosa master pump, the end of injection is constant except for the advance. The beginning of injection takes place earlier as you come under load due to the governor opening the metering valve, giving engine more fuel. The more fuel it gets the farther out the pumping plungers are forced. That causes them to contact the cam ring earlier so it starts injecting fuel earlier in the cycle. Why IH chose to tell us this was not good, and turn around and use the speed advance is for the engineers to answer. Apparently, due to the increased rpm's the hydro runs they felt the load advance did not meet their requirements. The speed advance is normally not nearly as touchy and need as frequent adjustments as the load advance but it can cause the same symptoms if it does not advance enough. That is usually a miss at higher speeds and works fine under load. Both advances are operated by fuel pressure so if you have low fuel pressure it will not adjust up correctly. You have to put a window on pump to watch advance or have a pointer device which I guess is easier to read, never had one. Of course static timing is just as important and if automatic advance is working correctly you can play with that a little, not much though. Also, a timing light for a diesel does not work on a Roosa master system due to the constant end of injection. I live out here in western Minn and don't do much tractor work any more. . Too old.
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Today's Featured Article - Talk of the Town: How to Remove a Broken Bolt - by Staff. Another neat discussion from the Tractor Talk Discussion Forum. The discussion started out with the following post: "I have an aluminum steering gear housing with a bolt broken off in it. The bolt is about a 3/8" x 1 1/2" bolt. I've already drilled the center of the bolt out with about 7/64" drill bit the entire length of the bolt. Only one end of the bolt is visible. I tried to use an easy out but it wasn't budging and I didn't want t
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