Jerky hydraulics when lowering boom only.

Yoladamama

New member

Equipment
L4200 GST, LA680
Feb 24, 2019
2
0
0
OCALA, Florida
Greetings. New to this Forum and here's my issue. I have a Kubota L4200 GST with a LA680 loader on it. My steering is smooth, the 3pt with bush hog attached operates smooth, my loader goes up nice and smooth and my bucket rolls nice and smooth but when lowering my boom on the loader it jerks violently. I can lower it VERY slowly and it want jerk but anything past SLOW it jerks like crazy. Has anyone had this issue and if so what was the fix for it. This thing is driving me crazy.
 

G.rid

Member

Equipment
L48 tlb, ssqa forks, manual thumb for hoe
Aug 19, 2016
207
17
18
Oxford, NS, Canada
Mine does it at times with a load. Never narrowed it down to when or why. I suspect mine has to do with the auto level block, it's out of adjustment and just haven't made the time to fix it.

Does your loader have auto level? Might help narrow down where to look.
 

Yoladamama

New member

Equipment
L4200 GST, LA680
Feb 24, 2019
2
0
0
OCALA, Florida
No on having auto level. Mine is jerky all the time. I did find a heavy leak this afternoon at the hydraulic steering cylinder. Thinking that maybe I'm getting air in the system from that ??? Anyway, I ordered the seals and o-rings this evening to rebuild the cylinder.
 

lugbolt

Well-known member

Equipment
ZG127S-54
Oct 15, 2015
4,924
1,652
113
Mid, South, USA
Usually if you have air getting into the oil, it will be jerky in all directions...up, down, curl, and dump--as well as 3ph lift and power steering since it all works off the same pump.
 

North Idaho Wolfman

Moderator
Staff member
Lifetime Member

Equipment
L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
Jun 9, 2013
29,148
5,442
113
Sandpoint, ID
No on having auto level. Mine is jerky all the time. I did find a heavy leak this afternoon at the hydraulic steering cylinder. Thinking that maybe I'm getting air in the system from that ??? Anyway, I ordered the seals and o-rings this evening to rebuild the cylinder.
A steering cylinder leak will not induce air into the hydraulic system, it takes a leak on the suction side of the system to do that. ;)

Try swapping Quick disconnects on the lines, as a bad spring on a disconnect can flutter and cause issues like that.
 
Last edited:

Shanester

Member

Equipment
B7500HST MX5100HST
Sep 21, 2021
77
34
18
Ohio
Greetings. New to this Forum and here's my issue. I have a Kubota L4200 GST with a LA680 loader on it. My steering is smooth, the 3pt with bush hog attached operates smooth, my loader goes up nice and smooth and my bucket rolls nice and smooth but when lowering my boom on the loader it jerks violently. I can lower it VERY slowly and it want jerk but anything past SLOW it jerks like crazy. Has anyone had this issue and if so what was the fix for it. This thing is driving me crazy.

This is exactly what my MX5100 did the other day moving about 20 tons of #2 limestone. Did you ever figure it out? While looking for a thread here with my issue I did see that similar issues were resolved by moving the 3PH down a tiny bit from fully raised. I'll try that today or tomorrow when I use it again. If that is the case then I suppose the feedback rod needs adjusted? I have the 6' rotary cutter on there and was in the fully raised position. My fluid looks nice and clean in the sight glass and according to the previous owner was changed a little over 100 hours ago.
 

Shanester

Member

Equipment
B7500HST MX5100HST
Sep 21, 2021
77
34
18
Ohio
I was using my MX a few weeks ago and the loader started getting jerky and weak. The brush hog was on there and I had it lifted all the way up. After a while I remembered this thread and dropped the 3 point hitch just a tiny bit and sure enough the loader worked great after that! Now I would like to adjust the feedback rod but I have not looked at what it entails yet.