Backhoe Jinma LW-6

   / Jinma LW-6 #1  

trelli

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May 13, 2010
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Hello all,

Been reading from the website for a while prior to purchasing a Jinma 354 and loader and backhoe. I haven't got my experience with hydraulics but something does not seem right about the backhoe. It doesn't have any grunt. Barely able to pull itself up with no load. I've read about possible valve issues and I'll look into it further. Just wondering what sort of RPM should the tractor be doing to work the backhoe properly?

The backhoe has it's own PTO pump the CBN- E3-25 at 25ml/rev. And what PTO speed are you using?

thanks
Mick
 
   / Jinma LW-6 #2  
1500rpm should make the hoe work fairly well. The chinese hoes are known for bad O rings at the connections. You may also want to check/change the hydraulic fluid and make sure everything is clean.
 
   / Jinma LW-6 #3  
The LW-6 that I used to have had a lot of debris in the hydraulic system - kept getting stuck in the relief valve. After a good flush and fresh oil that problem was solved, then it started going through O-rings and piston seals.
I solved that and any potential issues by getting a LiTW backhoe and never looked back.
 
   / Jinma LW-6 #4  
Just wondering what sort of RPM should the tractor be doing to work the backhoe properly?

The backhoe has it's own PTO pump the CBN- E3-25 at 25ml/rev. And what PTO speed are you using?

The nominal rpm should be 2000 for these pumps. However, you only get 540/1000 rpm at the PTO, at about 85% of the enginens max rpm. I therefore anticipate your pump has a gearbox.

Ref:
 
   / Jinma LW-6
  • Thread Starter
#5  
Thanks for the replies, good information. I'm here in Oz and there doesn't seem to be a market for the Korean BHs. Infact the market for Chinese tractors is very small and if I were to purchase a BH other than the LW6 it would have been impossible price wise at around $7000.

I got this tractor off a manufacturer at Alibaba. They manufacture implements which they add on to various other tractor makes. However on closer inspection the BH is basically a copy of the Jinma, I believe the valves /pto pump etc are the same although the boom seems a little different.

Getting this BH running reliably will have to be my option.


On the point of revs, if the pump says its output is 2000rpm, then at what PTO speed will this be acheived? And more importantly what engine rpm will get the PTO speed?
 
   / Jinma LW-6 #6  
PTO Gearbox

"PTO gearboxes use a gear ratio to increase the speed of drive from a tractor PTO to a higher speed more suited to hydraulic pumps. Typical applications are when the oil flows & pressures required to drive implements or machinery cannot be obtained from the existing tractor hydraulic system."

Units provide a step ratio of 3.5:1 & conform to the SAE standard J178D

3.5x 540 rpm = 1890 rpm, which is 5.5% less than the nominal 2000 rpm for the gear pump.
540 rpm at PTO on our Foton tractor is received when the rev. is 85% of 2400 rpm (=2040 rpm).
There is also a min spec for the pump, which was mentioned in my previous link to be 900 rpm (actually there says 'MAX'?!)

The min rpm specified for the pump is 900 rpm, which corresponds to lowering the tractor engine rev. to 48% of its rated value: 971 rpm (=0.48 x 2040rpm). The idle engine rev. is 750 rpm on our tractor, so it obviously needs some rev. up to start the hydraulics working.

Ref:
 
   / Jinma LW-6
  • Thread Starter
#7  
Thanks for the info, veyr helpful. Where did you get the information from? Was it specifically referring to the JInma 354? Please excuse my hydraulics naivete, I'm trying to remember year 12 physics here. Irrespective of rpm the pressure should be the same right? It's would just move slower. E.g if I operated at 1000rpm, the BH will jsut move slower but with the same force behind it?

2000RPM sounds very high to run the engine without much load.

thanks
 
   / Jinma LW-6 #8  
So your pump attaches to the pto output shaft?

A hydraulic pressure gauge would be handy to help solve this issue. Last I recall, I think the valve on your hoe is similar to the one on my HW-03. I found a pretty simple way to attach a pressure gauge for testing. I was able to adapt an off thr shelf metric adapter to screw into the check valve in place of it's normal plug. On mine the check valve plug is located on the top of the left side of the valve block(where hose from pump connects). The plug on mine screws in flush and has a large slot in it to accept a large standard screwdriver to remove the plug. If your's has this, I can send you the specs to modify a standard adapter to fit this port.
 
   / Jinma LW-6 #9  
On the point of revs, if the pump says its output is 2000rpm, then at what PTO speed will this be acheived? And more importantly what engine rpm will get the PTO speed?


I think your looking in the wrong place for your trouble ?? When I had mine the BH would run fine even at low engine rpm speed {1200}. The problems I ran into were the same as what Bob Rooks suggested. I found garbage in the tank{which in turn ends up EVERYWHERE else} and the seals were a pain in the butt. I also had to clean the relief valve more then once. I'm not saying this stuff can't be fixed it just takes time and patience. I did finally get mine running with no issues, but sold it for something MUCH better{mini ex}. You can do as you please, but I'd start with cleaning and inspection. You can buy the seals fairly cheap{buy a bulk set} and have it on hand when/if needed. You should also drain flush and change hydro oil. Start with the simple low cost stuff 1st then work your way up.

Unless you pump is broke or not properly connected I'd move on. The tractor and bh are designed to work with this setup, even at low engine revs.
 
   / Jinma LW-6
  • Thread Starter
#10  
yes it's a PTO pump. I'll purchase a pressure gauge and do the flush. I really need to get some working knowledge with hydraulics.

Thanks for the help.
 
 
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