datlas 

I know that the Lezyne CNC Floor pump is all that, and I agree the pump itself is good.

But for reasons unknown, the screw-on head has been giving me problems of late. It seems that with certain valve/tubes, it leaks. The ones on my summer wheels worked fine, but my off season wheels' tubes and this pump are not a match made in heaven and it is driving me nuts!

Anyone else have this problem and found a good fix?

In case you need a picture, this is the type of pump head I have:

beatlebee 

Last year, I had that same problem. I returned it for another. The next one had a leak in the cylinder. I returned it. Fairwheel mentioned that they use a Spec. pump and haven't had problems. I swapped and haven;t had problems. Too bad, I like the Lezyne. I think that maybe there was a bad bunch made. (?)

Mumonkan

try a lil triflow on the oring(s)

also try using the 90º QR head, i hated that thing at first but now it is life. if it pops off, hold it on the valve for half a pump to get a seal and youre golden

theres also a new ABS chuck that just came out that might be worth investigating

Doug28450

Put some Loctite on the valve stem.

datlas 

BTW if I use the little black plastic thingie that goes on the end, it works ok but I really kinda like the thread-on chuck (when it works).

Mumonkan

threads might be a little borked, its made of soft aluminum and i think the brass stems are harder than that

did you check out the innards to see if all the orings are still there? i believe they give you a couple replacements (but if youre anything like me those are long lost to the abyss of the parts bin)

this is the new one, it connects/disconnects like any standard pneumatic tool hose:

3alarmer 

...
...the pumps at the co-op take a lot of abuse, and nothing stands up for more than a few months. Same thing, the pumps still work, but the heads fail, either gradually or instantaneously.

If everything you are inflating uses a presta valve, it's really hard to beat the old Silca brass head for bombproof reliability. If you need something that will also do Schrader valve service, there are a couple of replacement heads from other manufacturers that you can adapt to your pump, sometimes just cut and clamp, sometimes youi need to step up or down with an air hose adapter fitting.


Original Silca 24 0 Brass Pump Head Presta Valve | eBay



https://www.biketiresdirect.com/prod...LUzRoCbB3w_wcB

datlas 

Thanks for the suggestions. Will investigate. The new head looks nice too.

Mumonkan

if you really wanna get fancy you can get this jammer



its the willier of pump heads

joejack951

I can't remember the exact size but I have a pile of spare o-rings that fit the inside of the Lezyne heads having ordered replacements from McMaster Carr and received 100 of them. If you can't find your spares, let me know and I can drop a few in the mail. Hell, the ride out to Malvern to Wilmington is pretty nice. I could drop them off.

goenrdoug

Same problem, same pump. I got one of these for 10 bux:


No problem since.

https://www.amazon.com/gp/product/B002SJZ27M

rpenmanparker 

I admit to not being intimately familiar with the Lezyne head design. Many pumps I have had experience with could be brought back from a leaky head problem by putting a washer behind the o-ring. By taking up some of the slack space with the washer you force the o-ring to compress more when the head locking mechanism is actuated. That will usually improve the seal on the valve stem. You have to be sure that the stem will fit easily through the washer. If Lezyne's don't work that way, that trick won't help.

GuitarBob

Funny, my Lezyne started doing the same thing during the past few weeks. I keep meaning to lube the o-rings but when it's being pissy I am anxious to get on the road, so I manage. I never remember when I get back because I have the attention span of a newt.

And if I wasn't such a lazy ****, I'd go do it right now.

Drew Eckhardt 

The Kuwahara Hirame has great adjustable clamping action. I went through two pump heads before buying one, and regret not making the change sooner.



If some one with a Schrader valve ever visits you can use a Schrader to presta adapter from Canitoe Road

Ball Bearing

My alloy HP Lezyne Floordrive leaked until I put a bit of silicon/rubber friendly grease on the chuck O ring and it is much, much better. Sometimes I'll use a bit of spit.

I used a Silca pump for years and I never liked the brass chuck.

f4rrest

I have the same lezyne and it's leaked for years.

It's not really a problem. Air still gets into the tube just fine.

PotatoBear

I have a 2-year old Lezyne CNC floor pump with this head which I have liked using. It just started leaking so badly that I can't inflate anything. Took it apart and found that both O-rings on the li'l black vent valve were badly cracked. The one that seals around the Presta stem is pretty ratty too. If they ever gave me spare O-rings they are long gone. Bummer. Had I known I think I could have wicked some triflow or anything in around the small button.
I can probably track down O-rings but that's a large hassle so I'm going to shop around for a primo pump head.

GuitarBob

Yep, the O-rings wear out after a couple of years. If you have a good hardware store locally they might have them for 50 cents each. Lezyne also sells a replacement kit:

https://www.lezyne.com/product-fpump...hporingkit.php

Shipping will cost more than the kit.

joejack951

My nearly-three-year-old offer still stands. I have a bunch of o-rings leftover. Anyone interested PM me your address and I'll drop a few of them in the mail.

ppile

I too have started having this problem with a leaky seal on valve stem. Seems the presta tubes I now use are somehow different from the ones I have used in the past. My chuck is an ABS 2 chuck and Lezyne gave me a replacement ABS 2 chuck. The replacement has the same problem. I also have an older inline screwon chuck that has same problem. Seems the basic engineering design of their chucks is flawed. Off to the bike shop to find a non-Lezyne chuck...

datlas 

OP checking in, since my thread somehow got bumped.

I ended up getting the newer head pictured above and it works fine.

San Pedro

I sometimes have to tighten the part on the bottom, that is below the part that screws on to the valve because air will leave from the hose. Usually half a turn does the trick.

JohnJ80

Be careful if you run tubeless. A little sealant in one of those heads and they'll never work right again. I've been through two of them now and finally just gave up on the Lezyne pump because of it. Back to the pumps I have with retrofitted Silca heads. Silca is still the best head in the industry.

J.