Today’s puncture repair took about 20mins. Every time I use my Lezyne Pressure Drive pump, on unscrewing the presta connector, it ends up removing the valve assembly insert! I didn’t have my Leatherman with me, but managed to unscrew the assembly from the pump. Unfortunately without having something to sufficiently re-tighten the valve the same thing happened again and I was beginning to get cold!
Fortunately I had a second innertube, the valve stayed put and I was on my way.
As said this seems to happen all too frequently when replacing tubes. Anyone else had similar problems with this type of screw thread adaptor? I’ve checked the adapter and the threads are ok; its so annoying!

Yep, I stopped using my lezyne pump for that reason.

Use one of these to tighten the valve core and it’s not a problem. 🙂
http://www.chainreactioncycles.com/stans-no-tubes-valve-core-remover/rp-prod138109?gs=1&gclid=CPKEuJXJqs8CFWYo0wodO5ULCQ&gclsrc=aw.ds

Nope they can still unscrew after using them.

You’re not tightening it enough…
Never causes any problems for me with a few different Lezyne pumps. 🙂

http://www.chainreactioncycles.com/no-flats-presta-valve-key/rp-prod94759?gs=1&gclid=CjwKEAjw652_BRDfkebVrdOGkDISJAD0Q2Ru-i3UODVXmCdyBmPpQq6ieSjpn3Fpg8Q3VESkoOcdLxoC0kbw_wcB&gclsrc=aw.ds

Or one of those, a lot smaller- for what it’s worth my pump hasn’t undone a valve core in maybe five years.

I think Stu has the right answer. In the comfort of my kitchen, tightening the Lezyne adapter all the way in seems to work, as it tightens the value assembly too. Out on the trail, I was frightened of not having a working pump, with a valve adapter stuck in its guts and a long walk home! Many thanks for the replies and a gold star to ss Stu!

I found not screwing the pump tight on avoids the problem, enough to get the air in but no more.

Easy enough when you are used to it.

I don’t think that it’s a problem with the Lezyne particularly, it seems to be more of an issue with certain tubes. I won’t be buying Continental tubes again as I’ve had the cores come out with the dustcap!

Tighten them up and perhaps use some decent threadlock. My Lezyne pump also came with a Speedchuck adapter that just screws onto the normal pump end; you just push the chuck onto the valve whilst you pump.

I’ve found you don’t need to unscrew them as much as it feels. A couple of turns at most, and then it’s the friction from to o-ring you’re feeling. If you keep unscrewing at that point you’re unscrewing the valve core.

Handy little tip which has got me and a few friends out of this situation, if you have a multi tool with a chain tool on it, I have found that you can use the removable part to tighten valve cores.

Works with a Specialized and Crank Bros multi tool anyway.

I don’t think it was just o-ring friction; it didn’t seem to matter how gingerly I undid the pump, the valve assembly just started hissing and then would be stuck good and proper in the pump housing! Good point about the speed chuck, I think I may have one somewhere.