Just fitted a new Joplin post- when it's in the down position, if I lift by the saddle, should it extend? It goes back down with no resistance then when I apply downward pressure to the saddle.
yes - you should avoid lifting the saddle when the post is down.
The suction can pull air past the seal meaning that when you drop the saddle, it will not sit at the stop, but extend up again a little... but without resistance if you push it back down...
If this happens, pull the lever to open the valve and push it all the way down and undo the seal lock ring a little to "burp" the system. Re-tighten the seal lock ring (just finger tight, don't over do it) and you should be good.
don't lift by the saddle without releasing the lever - you are pulling against negative air. it could roll the seals and bugger it up
cheers. Gave me a bit of a surprise. Won't be doing that again.. I'd just changed the shaft outer to the 31.6 from 30.9, and thought I'd buggered up something.