OK....This one will be winded.. This machine is a '79, 51U machine with dual variable pumps plus a gear pump for swing and pilot. Got the boom cylinder rebuilt and back in the machine. Also welded the bucket cyl hard line, replaced all the oil with what came cheap (15w-40 engine oil), replaced all filters, signal line fore rear pump still plugged, Oring on hydro tank replaced, relief valve reworked and tested in my shop, etc. I purged cylinders by just cycling them in and out slow at idle. All functions sound very good, speed of functions appears to be close to spec from the book test speeds. With signal line plugged on pump, it will pull engine down but nothing close to a stall but I don't stay in it against a stop. Pulls down more than other pump with servo hooked up. I am inclined to leave the servo right now until we get a few more bugs out and I can get it in some dirt to see what we have. here are the issues. 1. Seems boom load check might have problems. On several occasions when boom was near the ground, I pulled back on the stick and the boom dropped before going up. If this indeed indication of the load check, I would like to know how much oil will be lost rebuilding it? From the books, it looks like that one "might" be one of the easier ones? 2. ALL functions to me seem very rough and difficult to control. For instance, if I want to lower the boom slow, it will start very nice and slow if I sweet talk the control carefully. Adding more control, it will quickly accelerate and be too fast. I would consider all these functions to be similar to an "all or nothing" kind of response. They will all inch if talked to correctly but VERY difficult to operate smoothly.. I attempted to scoot a RR tie on the ground and could not do it. Trying to sweet talk the stick and boom together was more than challenging. However, Digging fast enough on air and once moving, it seems better. The same applies for stopping. They don't want to slow down, just stop. Jerky to say the least and that is going to wear stuff out. 3. Swing acts similar to cylinders. It will inch real nice but don't seem to have that nice acceleration/deceleration. Stopping smooth is near impossible and certain to punish the swing drive. It is already a little sloppy but I don't want it any worse. 4. Cannot operate the bucket and boom together. I am not sure if this is just how they were but this will certainly throw me for a loop in operating the machine. You know the bucket and boom use the front pump. It really seems like a valve shuts off or something because if that bucket is moving at all, the boom says hell no. The second you stop the bucket, boom takes right off. Boom is 2 cyl and moves pretty fast so fail to see how it could not move at all. Only thing I can think of it oil is going to path of least resistance and boom is heavy, bucket is not. However, this still seems problematic for proper function. I cannot help but think all these glitchy control functions have something in common from pilot pressure, air somewhere, pilot valves all hammered, main valve issues, etc. I have not got a chance to test pressures yet but I am headed that direction. Any direction or advice in testing these issues above would be appreciated!
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