I have a 1997 -751 bobcat that stalls out after awhile with the front aux hyd. on. If the throttle is kept high, when using the tree spade, the shovels are straining and dragging the engine down. I figure it's some relieve valve that is sticking. I have been told on line that there's a couple of coils that have a stem that drops down and needs to be cleaned or replaced. The guy that advised me has no idea what kind of dummy he's talking too. I read all through the service manual and can't figure what he is talking about. I had a Peugot diesel in it before and replaced with a new Kubota engine and did everything myself. But looking at that control valve is like my wife looking down a 4 barrel carb....Help.......Dean
751 bobcat hyd control valve
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SSdoxie
Elite Member
If you could understand the instructions (which leave a lot to be desired) and but the Kubota change over engine in there by yourself, you are no Dummy.
The 2 valve stems your guy mentioned are easy to locate, although I don't think this is the problem. Flip the cab up and you will see the control valve on Right Hand side of the machine (your left when standing in front of it), on the valve are 3 magnetic coils with wires connecting to them. 1 of these is low down, towards bottom of the valve, the other 2 are towards the top and these are the 2 that work the front Auxiliary.
If you push the front trigger to run the tree spade then control the blades with another valve, unscrew the thumb nut on each of these solenoid valves, lift the magnetic coil of the stem, then unscrew the stems and swap them. Put front 1 in rear and rear to the front. If the 1 stem was dragging it will now be on the side of valve not being used and problem should go away. To find out which stem is active with right handle trigger in detent mode. turn the key on activate auxiliary hydraulic switch the pull the trigger. Then try to slide each magnetic coil off the stem, the one that drags on the stem is the one that is active with trigger in detent.
The 2 valve stems your guy mentioned are easy to locate, although I don't think this is the problem. Flip the cab up and you will see the control valve on Right Hand side of the machine (your left when standing in front of it), on the valve are 3 magnetic coils with wires connecting to them. 1 of these is low down, towards bottom of the valve, the other 2 are towards the top and these are the 2 that work the front Auxiliary.
If you push the front trigger to run the tree spade then control the blades with another valve, unscrew the thumb nut on each of these solenoid valves, lift the magnetic coil of the stem, then unscrew the stems and swap them. Put front 1 in rear and rear to the front. If the 1 stem was dragging it will now be on the side of valve not being used and problem should go away. To find out which stem is active with right handle trigger in detent mode. turn the key on activate auxiliary hydraulic switch the pull the trigger. Then try to slide each magnetic coil off the stem, the one that drags on the stem is the one that is active with trigger in detent.
Hey Dennis, I have been studying this situation to death before I make a move. Just thought I would mention that the spade works with the aux hyd, it just strains. I felt it was a relieve valve because when the engine starts to drag down, it still wants to stall even when I turn off the Aux. hyd. With the bar up and no call for hydraulics, the engine stalls when I throttle down. Now if I turn on the aux hyd and hit the tree spade, the engine strains like it can barely handle one shovel at a time...I have been hooking up a 40" spade on my 963 and it works great. If I could make the 751 work properly, I would be cruising. Like I said, it works for a short while, then starts to load up..Heat issue making a valve stick. I think it's so cool that you take the time to help out some dumb Hill billy tree planter.....Dean
SSdoxie
Elite Member
Could be a number of things, but sounds like one of the Auxiliary stems is sticking or the return spring in the Auxiliary spool is broken/not bringing spool back to neutral.
