Bouncing 3point on a 9N

gears

Member
So I have a 9n that I rebuilt the hydraulics on 2 yrs ago (honed cyl, naa piston and rubber ring with backer, lapped chamber valves, checked pump piston & scotch yolk, removed lift arms & quadrant). Anyhow, since then I can't seem to lift as much as I used to be able to. The lift struggles on heavy stuff a 4'x4' crate of firewood (cherry) used to pull the front end off the ground. Now it struggles and bounces when it does get it up.

Near max lift it drops down almost a foot and then lurches back up, only to drop again. Searching the forums (archives too) I can't find a specific staring point. I'm leaning towards a bad relief valve - no, I didn't put a new one in at the rebuild. I compared parts from 3 pumps to use the best pieces on one.

I kept thinking it was my preload adjustment on the top link draft spring.

Opinions, experiences?
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Gears.........sounds like yer LOW on hydro-tranny fluid. (5-gals) Howsomevers, yer lift cylinder could also be leaking too much. Me? I'd remove yer 6"-roundy dipstick plate and look fer squirts. Iff'n ya gotts squirts, guess what? Ya honed out yer cylinder too much and will need a NEW one. While the NAA O-ring with leather backer is the piston of choice, it won't fix over-bore. Byte the bullet. NEW CYLINDER......respectfully, the amazed Dell
 
Gears,Yes it could be a bad relief valve or it could have trash caught in it causing the lift to drift down.You can check it by removing the inspection cover and raise the lift with a load ,hook a say 3' length of tight fitting hose slid over the end of the relief valve and see if it is bypassing or leaking past the valve.
 
I agree.. look for leaks first.. cyl mouth and relief are possible as are gaskets and stand pipe.

You could also pressure test her.
 
Over loading the lift can cause the control valve to tend to stick. Thus when the control valve would normally be pulled out of it bore, instead it
hangs in till it finally is yanked out of it bore and drops back to where is should be.
The oil being either dirty or with water in it can help cause it to perform this way.
Any time you have a load that tends to lift the front wheels is too much load for an N tractor.
Zane
 
I agree Zane, but I'd still like it to lift near capacity... Haven't checked the fluid level yet, I bought a new relief valve last year and haven't put it in. I figure if I'm going to the trouble to open it and put the hose on the old one I'll just swap it then. I can watch for leakage then too.

Dell, the lift will stay up overnight even with a blade on it so I don't think it's the piston leaking - but I haven't verified that the lift cyl isn't leaking under pressure.

Heading out between the rains to go check the fluid level/cond before I lose my light.
 
Oil is full and clean. I'll pull the cover and check for leakage this weekend.

Thanks for the guidance guys.
 

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