9N Lift cylinder question

jklightner · Jan 13, 2018

So my friends' 9N (year unknown) won't hold the load up. Got the lift cylinder and piston out and the oddest thing. The piston is a 3 groove type, but there are O-rings installed, not metal ones. Piston miked out to 2.4995. Cylinder bore at 2.5070 at the opening. Using a in/out caliper, don't have anything to reach down and check middle or end. Any thoughts on this weird setup? Tempted to replace both and be done with it. Should I go with the 3 groove and metal rings or the one groove and O-ring? The cylinder doesn't look to bad, couple of inch long scratches that may hone/polish out.

R Geiger · Jan 13, 2018

If you go to the o ring piston I would replace piston and cylinder. O rings do not like a rough finish. you could just put new metal rings in what you have.

Bruce (VA) · Jan 13, 2018

If you have more money than time (or skill) just buy a new cylinder. It's very easy to hone out that cylinder too far.
75 Tips

TheOldHokie · Jan 13, 2018

(quoted from post at 15:32:39 01/13/18) So my friends' 9N (year unknown) won't hold the load up. Got the lift cylinder and piston out and the oddest thing. The piston is a 3 groove type, but there are O-rings installed, not metal ones. Piston miked out to 2.4995. Cylinder bore at 2.5070 at the opening. Using a in/out caliper, don't have anything to reach down and check middle or end. Any thoughts on this weird setup? Tempted to replace both and be done with it. Should I go with the 3 groove and metal rings or the one groove and O-ring? The cylinder doesn't look to bad, couple of inch long scratches that may hone/polish out.

The piston is spot on and was probabably replaced when the o-rings were added. I'll bet it was leaking down and someone decided he'd do a cheapie :roll:

The cylinder is .007 over. That is a LOT of wear and I am not surprised it still leaks - especially with the ill-fitting rubber o-rings.

I would not reuse either and replace both piston and cylinder using the o-ring piston. Do it right and you won't have to worry for decades to come.

TOH

Tim PloughNman Daley RIP · Jan 13, 2018

It depends on how badly worn the cylinder is from the original steel ring-type piston. I never heard of someone putting rubber O-Rings on an original 3-ring piston before. It could be why it leaks. The steel ring style piston groove diameters(s) and the NAA rubber O-Ring groove diameter are not the same. The NAA style piston that uses the rubber O-Ring also uses a leather backup-washer/wiper. Me? What I would do since I had to pull the top cover off anyway, is to replace bot the cylinder and the piston with new. Evaluate if the pump needs to be pulled too and rebuilt -why not, you've gone this far? That way it'll all be good for many years to come before it needs to be yanked again. I'd stay with the NAA piston, rubber O-Ring, and leather backup washer too, but if you want/need a new 3-Ring piston, I have a new one I'd gladly part with. Email is open...

Tim Daley(MI)

jklightner · Jan 20, 2018

(quoted from post at 11:45:44 01/13/18) It depends on how badly worn the cylinder is from the original steel ring-type piston. I never heard of someone putting rubber O-Rings on an original 3-ring piston before. It could be why it leaks. The steel ring style piston groove diameters(s) and the NAA rubber O-Ring groove diameter are not the same. The NAA style piston that uses the rubber O-Ring also uses a leather backup-washer/wiper. Me? What I would do since I had to pull the top cover off anyway, is to replace bot the cylinder and the piston with new. Evaluate if the pump needs to be pulled too and rebuilt -why not, you've gone this far? That way it'll all be good for many years to come before it needs to be yanked again. I'd stay with the NAA piston, rubber O-Ring, and leather backup washer too, but if you want/need a new 3-Ring piston, I have a new one I'd gladly part with. Email is open...

Tim Daley(MI)

Whoever did it didn't use the NAA o-rings. I think they probably went to NAPA and just found some to fit. They also used RTV instead of a gasket on the cover. Got my parts from YT, didn't realize the gasket set came with the o-ring and washer, and I had ordered them separately. Now I have spares. Also found the draft control plunger bent, the spring plate buggered up, the bushing that goes inside the draft control spring cracked, and no felt washer. Got some parts coming from MO where a guy had a lot of lift cover parts on eBay for $20. The owner and I talked about overhauling the pump, but the "if it's working don't mess with it" won over the "as long as we're in here this far" idea.

jklightner · Feb 2, 2018

Just a note to close this out.
New Lift cylinder and piston. Didn't realize that the o-ring and leather washer came with the gasket set, so I had ordered separately. Now he has a spare set. Washer went on easy thanks to the soak in water tip. After getting it all back together, tested beautifully. Before, it was BANG, full up, or BANG, full down. Now he has control and can raise and lower nice and easy and hold the level he wants. Guess that's because the draft control plunger is no longer as crooked as a dog's hind leg. And a new friction disk for the control lever means he won't have to mow with one hand holding it all the time. I wasn't to thrilled with the scratches on the hydro pump pistons, but he didn't want to open that can of worms at this time.

R Geiger · Feb 2, 2018

The 9n and 2n were not designed to have position control, full up or full down and and chase what ever you want halfway.

Royse · Feb 2, 2018

"The 9n and 2n were not designed to have position control, full up or full down and and chase what ever you want halfway."

Correct. Limiting chains are used to set the height for a mower on a 9N.
Lower the mower and let the chains hold it at the desired height.
Or, buy add-on position control, like the Zane Thang from fellow forum member Zane Sherman.
10 minute bolt on job with no modifications to original equipment.

9N Lift cylinder question

jklightner

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R Geiger

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Bruce (VA)

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TheOldHokie

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Tim PloughNman Daley RIP

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jklightner

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jklightner

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R Geiger

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Royse

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