Timberjack 380 grapple

[Solo33]

I just bought a late 80's grapple. I'm having issues with the grapple itself not staying closed when I have a load. I keep having to hit the lever to close it tight. Any ideas on a fix for that? 

[kiko]

One of your grapple cylinders  piston could be leaking.  Wear in valve spool. We use to install a hydraulic lock valve as parts for that Cesna valve were hard to get.

[Solo33]

I'll look into a lock valve 

[C5C Tree Farmer]

If possible it would be best to isolate where the internal leak is located. A lock valve would be of a benefit if the problem is in the valve but there will be nothing gained if the cylinder piston packing is bad or the bore is scored and is allowing pressure to migrate from one side of the piston to the other.