Jinma 284 3 point question

[tigers2007]

I too was having the same issue. I just cleaned out the little valve and replaced it.

When I adjust the valve to allow it to raise, it won't lower unless I loosen the valve. Even if I fine tune it to the point where it will barely raise, I can watch it slowly drop. If I tighten the valve a little bit more, it holds its place BUT it is too tight for it to be raised.

Does that indicate that I should replace the seals on the 3-point cylinder with the kit I bought from Affordable?

 

[Diamondpilot]

I too was having the same issue. I just cleaned out the little valve and replaced it.

When I adjust the valve to allow it to raise, it won't lower unless I loosen the valve. Even if I fine tune it to the point where it will barely raise, I can watch it slowly drop. If I tighten the valve a little bit more, it holds its place BUT it is too tight for it to be raised.

Does that indicate that I should replace the seals on the 3-point cylinder with the kit I bought from Affordable?

Do you have a implement on the 3 point? It will not usually drop without a item on the 3 point.

Chris

 

[greg_g]

When I adjust the valve to allow it to raise....

That's not what it's for. The lift raises hydraulically, but is a gravity drop. The valve only controls the rate of fall, not lift

//greg//

 

[tigers2007]

Yes I have a heavy back blade on it now. So Greg, if I adjust the valve to have a reasonable gravity drop time, the whole issue of it dropping on its own is a whole separate problem?

I noticed that if I turn the valve half a turn counter-clockwise (therefore tightening the valve), it prevents the 3 point from slowly dropping down.

 

[greg_g]

the whole issue of it dropping on its own is a whole separate problem?

Yes, and a very common one on the 200 Series Jinma at that. It's typically caused by raising the rear lift too high; either with the lift lever (Jinma claims that's what the thumbscrews are for) or by bouncing down the road with an implement held too high. The higher the lift, the farther the piston travels in an open-ended cylinder. The cylinder isn't long enough to accommodate full piston travel, and - at the extreme - the piston O-ring and wiper(s) extend past the end of the cylinder. The act of lowering the lift retracts the piiston, at which time the O-ring and wiper(s) are damaged. From that point on, leakdown occurs.

On some Jinmas, there's an internal stop bolt that's also supposed to prevent over-extension. The operative word is "some", so there's a chance you don't have one. And it's also been found on some that do, that the stop bolt was adjusted wrong (in that it still didn't stop the over-extension in time).

Knowing how common the problem is, I doubt there's a Jinma dealer in the world that doesn't carry a shelf full of the lift cylinder repair kits. Not an expensive or complicated job, just time-consuming and messy.

//greg//

 

[tigers2007]

Thank you for your insight Greg. I'm glad I purchased the kit from Affordable and I'll fix this up as soon as it gets above freezing.

 

[greg_g]

Since you're dealing with Tommy already, he might be able to shed some more light on the internal stop bolt feature. With luck you'll learn whether or not your tractor has one in the first place. And if it does, whether there's enough adjustment in it to prevent this from happening again.

//greg//

 

[bluechip]

If closing the valve that controls lowering speed prevents it from dropping, it is not the piston seal/rings. The knob will not affect that. It is in the valve that controls lifting and lowering, it is not sealing in the centered position or not centering completely. Closing the knob holds the oil in the cylinder, regardless of the control's position. leaky piston seal will allow the 3 point to drop regardless.

 

[Affordable]

Chip is correct,I would bet on the lift valve bypassing too. There is a stop pin on the rear cover,it's not adjustable that prevents the lift piston from extending out too far and damaging the O-rings and wipers,this would allow your lift to drift down even with the valve closed,

Tommy
Affordable Tractor Sales
"Your Jinma Parts Superstore"
Home of compact Jinma, Foton, and Koyker Tractors and Parts, Wood Chippers, Backhoes - Affordable Tractor Sales Company

 

[tigers2007]

Okay so it appears that it might be the hydraulic lift valve then. Is there a rebuild kit for this? I can't find anything on Tommy's web site except for a new valve assembly.