I've got this old offroad forklift and when I get a heavy load on the front, the cylinders that control the mast tip slowly leak down. Would one assume the cylinders need rebuilding or possibly the hydraulic valve itself? No oil leaks out anywhere. The other thing is that even when empty, trying to tip the mast back dogs the engine terribly, like it's fighting a heavy load, but everything looks factory. Acts like the hoses on one cylinder might be reversed. Does this tell us anything about either the hydraulic spool or the cylinder?
Also took this to show the big ash log I cut today, but now it doesn't look so big. 33" diameter small end (this picture is looking at the small end). Quarter sawed it into 8/4 stock. Have had some luck selling it that way. Found a nice bolt smack dead in the middle. Must have put it into the tree when it was 3" in diameter. Hard to make that cut through the middle when I've only got 28" between the guides. Bunch of fiddling to get it slid over the dogs enough.
(Sawing and Drying Forum)
From contributor A:
It sounds to me that the spool valve might have something stuck in it. I had both the tilt cylinders for my forklift with a stroke of 4.25 lengthened out to 8 inches. If memory serves me correct it was about $450.00 per cylinder. Well worth the money. I now have 30?of travel at the tips of my 60?forks. Works great for digging out logs I wish to cut from a pile. I also had a hydraulic leak and took the spool valve to my favorite shop and it turned out to be a 50 cent O ring. It was $100.00 to check out the spool valve and test it.
I have had all the cylinders rebuilt on my forklift and when I asked about bleed down of the main mast cylinder I was told the spool valve would have to be replaced because after 50 years and dirty fluid it slowly wears out the valve body assembly. So always clean hydraulic filters once a year, and you should replace the fluid at that time. I never do that, but when I rebuilt the hydraulic system 4 years ago, I scrubbed out the inside of the tank and flushed out all the lines and pump. It is almost never left outside to keep the moisture out.