naa hyd piston / old vs new

souNdguy

Well-known Member
i've heard the original naa hyd piston for the oring was shorter than the one we normally use today.. anyone got the measurements of the 2? i'm helping a guy redo a lift on a naa that he has done 2x now and he says it keeps eating hte oring.

i havn't seen his bore.. so it may be scored and eating it.. but thought about that piston issue as well.. figured I'd measure it when he pops it out and see if he has the short one.
 
Section 128 on page 40 of manual FO-19 describes the o-ring and leather back-up ring installation procedure. I assume you have a copy of that, but if you need it, I could type it in here if that would help.
 
No need to measure. On the old pistons, the O-ring groove is closer to the bottom of the piston, and if the piston slides too far out of the bore, the sharp edge of the cylinder can chew up the ring. On the newer pistons the groove is farther up the piston and that can't happen. If you look at the piston it'll be pretty obvious which you have.
 
you guys are missing hte point.

i'd done plenty of top covers. what i NEEDED was the measurments of the piston to see if this guy has the old piston or needs to BUY a new one.

I don't have a NEW one in my hand to set down to his to compair too..

thus the request for the measurement, so when i pop out the piston, i can MEASURE IT.
 
you guys are missing hte point.

i'd done plenty of top covers. what i NEEDED was the measurments of the piston to see if this guy has the old piston or needs to BUY a new one.

I don't have a NEW one in my hand to set down to his to compair too..

thus the request for the measurement, so when i pop out the piston, i can MEASURE IT.

if you don't know it.. fine.. just say so.
 
Soundguy, you don't need measurements to compare, as the two don't look at all alike. If you have an FO-19 manual there's a picture on P. 40 that shows both. The new one has the groove halfway down the piston and the old one has it two-thirds of the way to the bottom. The new one also has a great big raised flat on the top and the old one has a little tiny bump. If you type "NAA hydraulic piston" into Google Images, all the pistons you see on the first page will be new-style ones, and if what you pull out looks at all like that then you're okay.
 

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