I am about to look into upping the loader relief on an '85
L2550.
I suspect the spring is "tired" or broken. This is the BF400G loader.
I do not know the spec for your loader, but I suspect it is about 2200psi.
You need to check that at the cylinders first. A metric fitting
for your gauge is reqd. Then you can replace the spring or add shims.
IMO, the Kub loaders should be able to handle 2500psi, as my JDs
do. The JD loaders I have are not built as stout. I do not know why
the Kubs are set so low. Check you pressure and report back.