Backhoe Jinma LW-6

[trelli]

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

 

[20 20]

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.

 

[Bob Rooks]

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.

 

[traktorz]

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:

• CBN-E3XX Series Gear Pump - Hangzhou Jinding Hydraulic

 

[trelli]

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?

 

[traktorz]

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:

• PTO Gear Box - Hydraulic Equipment Supermarkets Ltd.

 

[trelli]

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

 

[RonMar]

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.

 

[20 20]

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.

 

[trelli]

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.

 

[trelli]

Just another question. how do you know id the relief valve is working for the BH or the loader? When the BH moves to its maximum position there is a bit of noise coming from the PTO pump. Does that noise indicate that the relief valve is working?

However, when I use the loader, in maximum positions whether it be the bucket closing/ opening/ lifting etc the engine bogs down and shudders, like its really straining. That does not sound like a relief valve working??? When I feel the shuddering I release the lever immediately.

 

[Diamondpilot]

A relief valve should give a squeal. If is bogging the motor down its not set properly. On my 254 I set the loader relief at 2400 psi.

Chris

 

[Smalljobs]

I followed the teachings of another member, 3RRL, whose great technical postings you can find. I installed remotes, another relief valve, etc.

The take away is this: I installed a relief valve right next to the pump output and routed the relief port to sump. I also installed a pressure gage and set it to relieve around 2300 or 2400 as per the manual that came with the tractor. After that, I adjusted the relief valves, one at a time, on the loader and logsplitter to relieve at a lower pressure, maybe 100 psi less than the primary relief valve.

By doing this, the system was working to capacity but still protected while each accessory was also working with suitable pressure.

Hope this helps.

 

[California]

Could this BH have been delivered with a 'pto pump' that actually is designed to go on the front of the crankshaft, and turn at that faster speed?

The talk of a 3.5 : 1 step-up gearbox inside a pto pump doesn't sound right. Maybe they shipped you what they had, not what you need.

 

[Bob Rooks]

If the pump has a step-up gear case and fits onto the splined shaft, then the PTO must be operated in the 540 r/m range (giving roughly the equivalent of direct engine speed). If the pump has a tang drive and bolts directly to the differential housing then it drives at engine speed and can only be clutched out (no neutral). If you have a Prince or Prince-type of pump that slips over the splined PTO shaft, it must be operated in the 540 r/m range.

 

[20 20]

Trelli; It might help us to understand better if you have some pictures? Is it possible for you to take some pictures of your tractor the BH and the pump setup?

 

[trelli]

Not sure if it's the step up type but I think there's more to it than inappropriate RPM. I had it going at 2000rpm today and the boom had minimal grunt pulling itself up, infact I gave it a little assistance with my right hand and it moved up faster.....like it's JUST getting it up. At those RPMS everything else operates with a surprising violence, the downward stroke is like some hydraulic punch in the face and the side to side motion is ridiculously quick. I did manage to feather it somewhat and maintained a dubious measure of control over the wild beast.

I'll get some photos up after work. I've just ordered a pressure gauge to see what's going on with the whole system. Regarding the loader, I had a little look today and I think What I was look at was the relief valve, I took a long end nut off and there was an allen key bolt inside, I didn't change any settings as I'm unable to read the pressures just yet, but judging from the bogging engine when hydraulics are at its max, it'd probably not set properly as suggested by a member.

The manual says nothing about operating pressures. It's more of a safety manual.

I'm scouring the forums looking for 3RRl's and other's posts regarding the LW6 and, it seems like a very problematic BH. However I have no choice so I have to make it work.

 

[Smalljobs]

Trelli - The 3RRL posts were not specific to your backhoe but those posts and Rob (3RRL) taught me a lot about hydraulics. I don't have a BH. Good luck.

 

[20 20]

One of my problems on mine was the seal that was on the relief valve up inside. I missed it the 1st time I took it apart. The BH acted odd, power everywhere except to lift the main arm. Once I fixed the relief valve seal everything worked great.

 

[trelli]

Just got a few photos here, it's been raining so I had tarps over them. There are a few items on that I cannot identify or recognise.Any help is greatly appreciated. The manual does not identify these.

thanks