I recently purchased a bobcat 853 with over 5,000 hours on it. I pulled the isuzu motor and rebuilt it completely. It runs smooth & strong, drives strong and the tilt seams to be working fine, maybe a little weak, but it works. The lift cylinder, however, only goes up when at full rpms and then only slowly. If I try to do anything else; tilt, drive, etc. it stops completely. If I have a load on it, it won't go up at all unless I use the tilt to give it a boost. It does go up all the way given enough time. I checked for leaks, but no luck finding anything yet. It's a hydro-static drive, so I think the pump is ok, and the tilt works alright (not weak, but not strong either, way stronger than the lift...), so what could it be? Could the cylinder's be bad? I'm new to anything hydraulic, but I've got plenty of hours wrenching, just need to know where to start. Any help would be appreciated.