Thought this might help somebody, We had an intermitant problem with the bucket hoist on our 623F. It would go up part way and either stop or go up very slow, next load would be OK then the next it would do it again and the 2 rams seemed out of sequence, it would lift the loaded scraper at idle so we assumed pump pressure was good so what's wrong? Dealer mech came out, all pressures checked good including pilot pressure. Main control valve spring is good, we thought there might be a internal leak in one ram and the other is doing most of the work. Long story short there is a check valve on the top of the rams and a small spring had broken into pieces allowing the check ball to seat intermitantly causing all the trouble. Of course the ball seat (casting) was ruined so I had to buy a new check valve but we got her fixed. All in a days work but sometimes you just have to scratch your head. Lots of complicated systems aboard a 623