Jinma LW-7 backhoe control valves

[pelicanme]

I know a lot of guys out there replaced their original Jinma backhoe controls. I've done the pto pump conversion, but have determined I have a problem with the control valve for the swing cylinders (since new). I've cleaned it, replaced the o-rings, and believe there's a manufacturing defect. Does anyone out there still have their old valves lying around, and if so , would they sell that valve block to me.

Thanks, Mike

 

[Affordable]

I have a few of the New Replacement backhoe valve assemblies that I got in a auction of a Jinma dealer that went out of business, I will make you a deal on one for $ 350.00 plus shipping,they are brand new never installed,however they are sold as is.If interested e-mail me at

tommy@affordabletractorsalesco.com



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

 

[RonMar]

What kind of problem are you having?

 

[Bob Rooks]

Remember, those are only single acting cylinders, and provide power in the retracting direction only.
Is the operation of the swing very jerky?

 

[pelicanme]

Hey Bob,

Just an update - I switched the hoses today, and with that done, I have super fast swing and poor left stabilizer. I guess that proves the bad valve theory. It's been that way since new, so I suspect it's just poor tolerances and quality control, the bain of Chinese tractors.

Mike

 

[RonMar]

What do you mean by "poor left stabilizer"? IS it slow, or lacks power? Was this the original problem when the boom swing was attached to that circuit?

If so, These valves use adapters between the straight metric threaded ports on the valve body and the o-ring face seal hose ends. The 2 adapters where the swing circuit hoses attach are machined differently than the rest of the adapters. They have very small 1/16" holes machined in them to restrict flow on the swing circuit to keep the swinging boom from accelerating too fast and jumping all over the place. The rest of the adapters are all drilled straight thru with large center passages. thats why the boom swung real fast when you powered it with the un-restricted stabelizer circuit.

I would unscrew the two adapters on the swing circuit from the valve body and make absolutely sure those small holes are not plugged, or that there is not some trash trapped behind them. This could be causing the problem with the cylinders when attached to that circuit.

 

[pelicanme]

Hey Ron,

Yes, I found the smaller restricter holes for that valve, and though I knew it probably wouldn't help, I drilled them out to a larger size. Everything was cleaned, and I replaced the o-rings. There was no change in performance. Basically, the swing cylinders both worked, but with very little power, and I could hear the the squealing of the high pressure fluid as it leaked through the valve. While all the other blocks registered full relief pressure, this one only built to about 30 percent. By changing the swing hoses to the left stabilizer block (leaving the nearly full opening restricters in place), the swing was powerful, although much too fast. The stabilizer which I connected to the swing block is now almost useless, it's so weak.

If I can find a used swing valve from a discarded Jinma control unit, I think that would take care of it. I'd also need the small restricter adapter to slow things down. Barring that, I'll probably buy the whole assembly from Tommy at Affordable, and have some spare parts.

Thanks for your input. I've learned a lot about hydraulics since owning this tractor, but I suspect there's more to come.

Mike