JD 650, a knob, a mysterious, alluring knob.

[dapeake]

Hi folks,

I'm newly joined, but want to thank you all for the past year of saving me time, grief, money and injury, but mainly money.

There is a 2" diameter knob below the seat of my 650 tractor. It is a valve that when closed traps the fluid inside the hydraulic actuator for the 3pt, thus locking it in place. This seems useful. But the problem is if I let go of the 3pt drop lever, it springs back to the up position and you hear a loud squeal, the engine loads wants to stall.

What is the utility value of this mysterious knob? If I must hold the drop lever to the exact fixed position it was in when I closed this valve it seems like a bike kickstand that only works if you hold the bike up at the angle it was at when you deployed the kickstand, or cruise control that stalls the engine if you do not maintain a precisely held depression of the gas pedal.

I thought it might be safety (preventing a drop when the engine is not running) but when you try to start the engine with the drop lever, strongly spring loaded int the lifted/up position, you can't start the engine the starter motor is over-loaded as the hydraulic pump is over pressuring the the main system over-pressure bypass. So you must either open the mystery valve, or actuate the down lever when starting.

I am prepared to be called dumb. I can take it.

Dan
Campbell
JD 650, JD 67 Loader

 

[AllByteNoBark]

On my 950 you use that t oadjust how quickly an implement lowers to the ground. Prevents it slamming down if it is heavy, if the implement is lighter you might open it more to allow it to lower quicker.

 

[ovrszd]

Welcome to TBN to both of you.

Yep, it's to control lowering speed of the 3pt.

I don't understand the pressure overload you describe?? The squealing is the pressure relief valve in relief.

 

[k0ua]

I am not totally familiar with your JD650, BUT this is what I think: You would only close off the flow rate valve if you wanted to "road" the tractor and you didn't want the implement to bounce around while on the road. You NORMALLY don't close, them you adjust them so that as you put light implements on you will have to loosen the valve so they will fall, and heavy implements on you tighten the valve (but NOT all the way) so that they don't fall too fast. NOW that all said. You apparently don't have position control on that little JD, but have some form of what Kubota would call "quarter inching", Long story short, it is manual control of the fluid flow to the cylinder, BUT with the cylinder all closed off (don't do that) the fluid had no where to go and the relief valve has to open up to prevent your pump from becoming a hand grenade. That is the squall you hear, the fluid flowing over the restriction of the relief valve. The 3pt control you have probably has an up and a down direction and a "spring" center or neutral. You tell me if this is wrong. So you would NEVER try to raise the 3pt with the drop valve all closed off. Don't do that. The only time it is OK to close the valve is when "roading" with an implement attached, BUT then you would not touch the 3pt control valve until you had loosened up the drop rate flow valve. Hope this makes some sense.

 

[ovrszd]

Good stuff James. I didn't catch the fact that he's closed the speed valve and then trying to use his 3pt. Good catch!!!

 

[k0ua]

Good stuff James. I didn't catch the fact that he's closed the speed valve and then trying to use his 3pt. Good catch!!!

That and you are used to tractor's with position control. I had a little Kubota about the size of his 650 that had that manual spring center neutral control setup. There is no position control function, Just up or down directions from the spring center. You could bump it quickly and that is what Kubot calls "1/4 inching" because it would raise or lower the 3pt in about 1/4 inch increments. Approximately. Of course it won't hold that position because there is no feedback mechanism to automatically hold position. You as the operator are the "position control" when you notice the implement is sagging down due to gravity you "bump" it back up a little. Then 15 minutes later you bump it again. As you know tractors are made to a price point. You don't get all the good stuff for a real low price.

 

[ovrszd]

That and you are used to tractor's with position control. I had a little Kubota about the size of his 650 that had that manual spring center neutral control setup. There is no position control function, Just up or down directions from the spring center. You could bump it quickly and that is what Kubot calls "1/4 inching" because it would raise or lower the 3pt in about 1/4 inch increments. Approximately. Of course it won't hold that position because there is no feedback mechanism to automatically hold position. You as the operator are the "position control" when you notice the implement is sagging down due to gravity you "bump" it back up a little. Then 15 minutes later you bump it again. As you know tractors are made to a price point. You don't get all the good stuff for a real low price.

Say it isn't so James!!! I here members on here all the time talking about how cheap they buy tractors that are equipped as well as the high price models!!!

 

[k0ua]

Say it isn't so James!!! I here members on here all the time talking about how cheap they buy tractors that are equipped as well as the high price models!!!

I know!. It is amazing isn't it. :confused3:

 

[dapeake]

Thanks for the input everyone.

"Transporting with a heavy implement" is probably it. However, the innards of the 3pt actuator cylinder includes a secondary relief valve specifically for the 3pt actuator which is designed to release fluid back into the sump upon abrupt vertical events during 3 pt operation or during a lockout via the mystery valve. In other words it is not fully locked.

I have a theory: Implement attachment. I often find myself in dangerous poses trying to manipulate or hold the up/down lever while kicking or pulling the arms onto the pins of my gannon box or drilling attachment. It could be that for safer implement attachment you would set the desired 3pt arm height, lock that in position with the mystery valve then shut off the engine, go back and kick things into position, open valve, restart engine. (Isn't turning a diesel on and off a bunch a generally bad idea?)

James - I am going to check out the Technical manual and study what is called feedback linkage on this tractor. I saw it, but I lack any natural resistance to ADD so I did not stop to understand it. I believe this JD650 is possibly equipped with a feedback mechanism to self regulate the position. Fascinating.

Drop speed theory: Good guess Richard and AllBytenoBark, but, on my 650 there is a small un-mysterious lever called "drop speed" that is located on the port side of the 3 pt housing. It is a valve that sits in the sump return path of the 3pt cyl.


Thanks,

Dan