8N Lift Problem

Hello. I recently had the top cover off my 8N to fix the typical leaking lift cylinder o-ring problem. Had to replace a worn cam follower pin and weld the cam back up to match its unworn edge while I was in there too. Also replaced the safety valve while I had it open for good measure. Got it all back together and verified that everything was moving OK and the control rod was moving the valve in the pump correctly before filling it up with fluid. Didn’t see any issues. Added fluid, fired it up and ran the arms up and down. All appeared fine.

Hooked it up to the brush hog today and picked it up no problem, but once I set it down it wouldn’t go up again. I pulled the inspection cover off and can’t see see any leaks. Stuck my hand down in the sump and verified that the control rod is in the cup of the rocket where it belongs, and it is, but the end of the rod is not moving when I move the touch control lever. I reached and verified the nut was on the end of the shaft that the control rod mounts to, but it’s as-if the rod is slipping on the shaft or binding somewhere.

I’m baffled here. Is there a common problem of some sort that would explain this? A bushing that wears, the shaft wearing, something with the control rod? Something I missed in reassembly (weren’t any parts left over)?

Any help is appreciated.

Thanks,
Adam

Sounds like it is time to remove the top cover and take a look.

I recently re-did my top cover and pump. Same thing - first couple of times it operated properly, so I attached the Bush Hog (tm) and did some mowing. After mowing a while the implement wouldn't lower. Removed the right side cover and found the control arm was stuck, for unknown reasons. Got a pry bar and pried it forward, and now the lift arms lowered. Could find no real reason for becoming stuck. The only odd occurrence was I had jammed the Bush Hog (tm) on crossing a gulley, mowing, and probably applied added stress to the lift arms. Been a couple of weeks, and hasn't happened since. Check to see if the control arm moves freely by hand, through the side cover. If not, gently pry it forward, and test again. zuhnc

Can't edit any of my posts. Yours won't raise, mine wouldn't lower. I did put a pressure gauge on the test port and got about 1200psi when lifting my mower. 5' Bush Hog (tm). You might check the pressure, if possible. Maybe the relief valve is stuck with debris/sludge, etc. That would prevent it from going up, but it would seem odd if you only removed the top cover and repaired the lift cylinder. Didn't leave out the retaining pin in the dog bone, did you? Good luck in finding the cause. zuhnc

If the control valve is stuck in the pump try and pry it free as zuhnc stated. Sometimes its a one time event then other times the pump will need to come out the bushings the exhaust valve runs in drove out and the oil circuit thoroughly cleaned.

This is a very basic simple job tho a dirty job it just requires work : (...

I’ll try giving it a gentle pry when I can get over there again this weekend, hopefully that’s it. Will also have to see if I can borrow a gauge to check the pressure. I changed the safety valve so it should be good, and I cleaned the sludge out so I’d be surprised if it’s clogged, but stranger things have happened.

Thanks.

I would not worry about pressure get the control valve to moving first...