8n lift repair

Reporting back on my 8n lift repair. When I finally got my 51 8n running I hooked up a 5 foot finish mower to it and started to cut grass. After about 10 minutes the 3 point lift could not keep the mower raised with the lift disengaged. Took it back to the shop and removed r/side inspection plate and with the tractor running and the lift raised I could see fluid streaming from the top cover at the hydraulic piston cylinder. I removed the top cover and removed the cylinder and piston and someone had already replaced the piston with the new type single o ring type but the wiper washer was missing. Ordered new o ring and new neoprene backup washer new safety valve and new gaskets. Cleaned out the hydraulic case honed out the hydraulic cylinder installed the new safety valve and put all back together. Also made the required adjustments and installed 134D universal tractor fluid. Now after two hours cutting grass the lift works fine and will stay in the raised position overnight. (JUST TESTING IT) Thank you all for the information and help.
 
Are you in DRAFT CONTROL or POSITION CONTROL? If the lift raises when the PTO is disengaged, you have other issues. How does the touch control lever figure in? I don't think the problem is in a missing backup/wiper ring. I have found several of these without it and they work fine without it. I suspect you have a bad cylinder, scarred from the usage of the old three ring piston and now has grooves in the cylinder wall that allow oil to pass. I would have replaced the cylinder when the top cover was off the first time, but that's me. I don't muck around with trying to 'hone' the old cylinder, just get a new one and replace it while everything is off. Did you put the control rod back into the right hole?
 
A proper hydraulic lift system will sustain a load up for weeks if not months. Don't judge by one night. Set it up with some sort of way to measure any drop.

Tim
 
I am sure that the cylinder after honing it out, it looked like maybe it was replaced when the new style piston was installed. If for a moment I taught it was defective I would have replaced both piston and cylinder. I really don't like doing things twice. I need to move on to the next item on the list of adjusting the valves and replacing the manifold gaskets. It is a late model 1951 so I hope it has adjustable tappets and the adjusters are not frozen. I have the adjustment tools; and if they will not work I will drill 1/8 inch holes to lock the tappets. Lets hope
 

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