limp wrist control - Kobelco MD200BLC

[Marksan]

Hello
l have a 1988 Kobelco, when i have my boom, stick and bucket out horizontally with the bucket facing the ground the bucket will come down through around 90 degrees to about where it would end up if just suspended with the face towards the cab, this takes around 15/20 seconds with the engine running at normal rpm or shut off.
lf i was to lift the machine up without the bucket curled in/up to the stick the weight of the machine will curl the bucket and then lift the machine.
Apart from that the wrist movement in and out is fine, the rest of the machine is fully functional in all other circuits, no abnormal sounds, movements, smells, digs great.

lts a farm machine so this isn't really the end of the world for what its used for, i would like to get it right though. Any input appreciated

Cheers

 

[willie59]

I'm trying to picture this Marksan. Let's see...you have the arm fully extended, bucket curled out fully and off the ground, in about 15 to 20 seconds, the bucket will curl in to a horizontal bottom digging position, engine running or not. Right?

This one, not sure what your describing...

"lf i was to lift the machine up without the bucket curled in/up to the stick the weight of the machine will curl the bucket and then lift the machine."

 

[Dan83]

ATCO, I think he means that if the bucket cylinder isn't fully retracted, and he lifts the machines weight with the bucket, the bucket cylinder/circuit is leaking down. That's what it sounds like to me... what do you think?

 

[Marksan]

Sorry Guys, try it another way.

lie stick on ground with bucket so that the mouth/opening is flat on the ground.

lift boom up so the stick is parelell to the ground, bucket will come down around 90 degrees in 15/20 seconds and stay there. ln perhaps the positon gravity would leave it, same same engine on or off.

lf i have the bucket curled up to the stick and the stick hanging down 12 thru 6 oclock, the bucket will droop down to the same 'neutral' postion as above in about 15-20 s

 

[TD-5]

Its quite possible the piston seals in the bucket cylinder are worn & by-passing. With the boom,stick,& bucket stretched out as you described, remove the hoses to the bucket cylinder & cap the fittings on the cylinder. Lift the boom up as before & if the bucket still droops down, the piston seals are by passing & the cylinder needs a rebuild. If the bucket holds position, then the problem is further back at the valve bank.

 

[Marksan]

Thanks TD 5,
lm going into to town tomorrow and will pick up some plugs and caps.

So i understand that i have to block the feed and return on the cyl for the test.

What should i be doing with feed and return lines on the machine to the bucket cyl, can they also be plugged for the test or do they need to be connected to form a circut?

Cheers

Its quite possible the piston seals in the bucket cylinder are worn & by-passing. With the boom,stick,& bucket stretched out as you described, remove the hoses to the bucket cylinder & cap the fittings on the cylinder. Lift the boom up as before & if the bucket still droops down, the piston seals are by passing & the cylinder needs a rebuild. If the bucket holds position, then the problem is further back at the valve bank.

 

[TD-5]

I am not familiar with the hydraulic design on your particular machine, but typically there should be no oil flow in the lines untill you actuate that circuit. However I would cap them to prevent the lines from draining while disconnected & loss of oil ( & a big mess) if you mistakenly actuate the circuit during testing.