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Zefal Hpx head rebuild.

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Zefal Hpx head rebuild.

Old 09-14-20, 02:31 PM
  #1  
rosefarts
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Zefal Hpx head rebuild.

I've got an Hpx from the 80s. For the life of me, I can't get it to stay on a valve more than a couple pumps.

I got this thing a few months ago basically unused since the 80s. A little lube on the innards and it pushes air great. Problem is, I can't keep it on the valve.

$5 rebuild kit, $6 shipping. It's made of a tackier black rubber than the original. Mine is off white and kinda slick. I'm not mixing up presta or schrader.

If it works, no brainier. I just wanted to double check that there isn't some problem inherent in the design and I'd be better to cut my losses.

Yes, I have a CO2, mini pump, and a Silca. This seems like a great candidate for town rides, my wife, back of kid trailer, etc. I'm a recent inductee to the frame pump club and so far, I like it better than the mini stuff except in very limited situations.

​​​​​​Is it worth fixing?


​​​​​
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Old 09-14-20, 02:53 PM
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fietsbob
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Up to you, not me, your time & effort..

the HPX is still being made , you could just get a new one..
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Old 09-14-20, 03:03 PM
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rosefarts
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Originally Posted by fietsbob View Post
Up to you, not me, your time & effort..

the HPX is still being made , you could just get a new one..
Yep. So is it unchanged? Does the new kit work on a 1987 model? I don't think a new one would push more air. It's only the head I'm worried about. $11 vs $42
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Old 09-14-20, 03:09 PM
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I dunno if it will work but it sure as heck looks the same. You could try writing Zefal and the tech people there may or may not reply to you or you could take one for the team and report back your findings. If you find a mail order place with a few more items you like, you should be able to get the shipping down to zero but you will end up spending more money, : )


https://www.modernbike.com/product-2...MaAvDlEALw_wcB
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Old 09-14-20, 03:31 PM
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My equally old HPX has a black rubber reversible (presta/Schrader) insert in the head that still seems pliable enough to work. I expect the kit you are considering is just that insert. Probably worth the cost to salvage the pump but mine just sits on the shelf as it's too heavy and bulky to take along.
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Old 09-14-20, 04:12 PM
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Juan el Boricua
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It will work; the pump hasn't changed in 30 odd years. The kit comes with seal (cylindrical rubber piece with a somewhat "closed end with a hole in it"), valve pin and valve cap. Do remember that you must turn the head's innards manually to fit either presta or schraeder (seal's wide open end+ pointed valve pin tip down=schraeder; semi closed/ hole in bottom end+open end of valve pin= presta). And you're good to go for another 30 years! ( mine's 10 years and counting with just piston lube job every once in a blue moon). Good luck
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Old 09-14-20, 04:56 PM
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Great pump. Worth spending a few bucks to save it IMO. Mine survived 20+ years of many flats and lending out to ham fisted gorillas jamming it against trees when pumping, breaking off their valve stems and returning my pump with the stem still stuck in the pump head, etc. Still works perfectly but I purchased a new mini pump so I could easily carry it with me when the bike is locked up and out of sight as the thieves like to steal the Zefal's. Just take it apart and clean/lube the innards every year or so and will last for a very long time and doesn't take 200+ strokes to pump up a 700c road tire.
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Old 09-14-20, 06:00 PM
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I would definitely fix it with the kit. I have one that I do not remember when I bought it. I now keep it in my bike work area for quick partial tube inflation. Like other posts, I have CO2 and smaller, lighter pumps.
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Old 09-14-20, 06:07 PM
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rosefarts
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Originally Posted by delbiker1 View Post
I would definitely fix it with the kit. I have one that I do not remember when I bought it. I now keep it in my bike work area for quick partial tube inflation. Like other posts, I have CO2 and smaller, lighter pumps.
Funny, I also have a Silca from around the same time, custom painted for the bike it came with. I weighs half what the Zefal does and works better. Due to the friggin Tom Kellogg paint job on it, I won't be dragging it around with the bike trailer and other knockabout rides.

The Zefal is that beater. I'm going to fix it. Now to buy new tires for one of my bikes to get free shipping?
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Old 09-14-20, 06:32 PM
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Silva’s are famous for sometimes exploding. The zefal will not. It can also pump to higher pressure. I like them both but the zefal is IMO the better pump.
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Old 09-14-20, 06:40 PM
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I had a double blowout and I was carrying one spare tube and a patch kit. I figured, I'm golden. I put the spare tube in the front wheel and proceeded to pump it with my Silca. Three strokes later, the Silca split in two. I rode 4 miles on both rims to get home. I've traded all my Silcas for Zefals
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Old 09-28-20, 01:50 PM
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I got the rebuild kit and it doesn't appear compatible.


This is the old pump head, in the order it assembles or disassembles.


This is the rebuild kit in it's entirety.

Using just the rubber pump head hasn't seemed to work. Since it is longer than the off white one I'm replacing, I could shave it down to fit.

The thing with the point doesn't seem to fit inside the part I would guess that it should fit inside.

It really isn't the same. Btw, I did get exactly what was advertised. Shame on me for not disassembling the pump before ordering.

Is the HPX different than the HPX 3?

Is there a way to make it work without another order?

Should I fill it with lead and call it a training aid?

Edit to add, the person who I got this from loved tinkering with stuff. It's possible that it's missing something.

Last edited by rosefarts; 09-28-20 at 01:53 PM.
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Old 09-28-20, 02:15 PM
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HPX3 is the size (length) of the pump. There used to be HPX1, HPX2, HPX3 and HPX4, all the same, just sized for different frames.

Did you buy the kit from Zefal?
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Old 09-28-20, 03:10 PM
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rosefarts
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Originally Posted by branko_76 View Post

Did you buy the kit from Zefal?
Directly? No. It is Zefal branded and is identical to every HPX rebuild kit available anywhere else online.

So if I reassemble with only the black rubber pump head instead of the white, and put teflon tape on the threads, it will work for presta. With leakage depending on the specific valve. Still faster than itty bitty hand pumps.

Looking at a diagram, mine might be missing a piece that's a lot like the pointed one in the rebuild kit but smaller.
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Old 09-28-20, 04:32 PM
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The guts of the HPX head changed, possibly more than once, over the years. I think the earliest heads were identical to the HP that the HPx replaced. These heads used different stacks of parts for presta and schrader usage, and you had to swap parts to convert between one and the other.

See: Zefal HP help

Later heads are reversible, and parts are as you received. I don't think the old parts are still available new. A few years back I was still able to find the part numbers for the older sets and the parts were still available NOS on eBay, but I can't find the part number now, and the parts supply seems to have dried up.

If you have the means to shorten your plastic plunger, you could probably make it work with the newer parts. I have access to an early HPX configured for schrader, so I could measure the gasket length and pin washer thickness - maybe next weekend - but my head might not even be the same as yours. From the diagram, schrader and presta gaskets appear to be the same length for the early heads, but your presta gasket looks shorter than my schrader, which in turn looks similar to the new reversible gasket.

If your head is the same as mine, then the difference between the lengths of my parts and your new replacements would tell you how much to shorten the plunger.
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Old 09-28-20, 05:12 PM
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Can you just substitute the new seal/tightness ring and pin, for the yellow tightness ring, springs and old pin? I thought so because the head casting appears the same between older and newer ones, and just the innards changed.
Since the cap only helps in the tensioning of the tightness ring, I do not see how adding teflon helps with sealing ( i'd guess it would hinder it as it adds friction/resistance as to adjust the cap for further tightening). Anyhow, good luck, as it is an excellent pump!
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Old 09-28-20, 06:00 PM
  #17  
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Originally Posted by Juan el Boricua View Post
Can you just substitute the new seal/tightness ring and pin, for the yellow tightness ring, springs and old pin? I thought so because the head casting appears the same between older and newer ones, and just the innards changed.
Since the cap only helps in the tensioning of the tightness ring, I do not see how adding teflon helps with sealing ( i'd guess it would hinder it as it adds friction/resistance as to adjust the cap for further tightening). Anyhow, good luck, as it is an excellent pump!
Of course I tried this first. Depending on the valve, it kinda worked but I lost a lot of air from the threads.

My 3 year old has guaranteed that I can never quite find what I need. No roll of teflon tape but a little sliver on a hose fitting I'm not using now. I used that and it improved the seal. On one wheel, it was perfect and on the other, it was okay. The air loss is coming from around the valve now, not the threads in the head.

Unfortunately, I have to change how far it's screwed for each valve or I'd silicone it in.

My idea is to have a more functional pump on my way out in the boonies bike, which this fits perfectly in.
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Old 09-28-20, 06:58 PM
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@rosefarts, I have at least three generations of Zefal HP and HPX pumps, I'm curious which one yours is. Can you post a photo of it?
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Old 10-01-20, 02:39 AM
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This is the complete innards of my Zefal HPX, not sure how old it is.

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Old 10-09-20, 04:25 PM
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Originally Posted by luns View Post
Later heads are reversible, and parts are as you received. I don't think the old parts are still available new. A few years back I was still able to find the part numbers for the older sets and the parts were still available NOS on eBay, but I can't find the part number now, and the parts supply seems to have dried up.

If you have the means to shorten your plastic plunger, you could probably make it work with the newer parts. I have access to an early HPX configured for schrader, so I could measure the gasket length and pin washer thickness - maybe next weekend - but my head might not even be the same as yours. From the diagram, schrader and presta gaskets appear to be the same length for the early heads, but your presta gasket looks shorter than my schrader, which in turn looks similar to the new reversible gasket.

If your head is the same as mine, then the difference between the lengths of my parts and your new replacements would tell you how much to shorten the plunger.
I had a closer look at my head, and between that and JaccoW's picture, I think my understanding of the later heads was wrong. Things look to be more alike between early and late than I previously thought. It looks like the plunger at the back may well be the same and what I said about shortening was completely off the mark. The black plastic spacer in the current kit, I previously thought stacks on top a shorter plunger, but after having a closer look at mine, it looks like it would actually nest inside. My plunger, despite being an older chuck, does have a 3.5mm step inside of it that the edge of the new spacer would rest on, with that much depth available for the Schrader pin to hide inside

So, I think a full conversion to the new parts would be to omit both of the springs and the metal washer of your original stack up and put the plastic spacer inside the plunger instead, but then you say it didn't seem to fit for you. The inner bore of my plunger is about 10.5mm in diameter - is the new plastic piece bigger than that? My Schrader rubber is 10.6mm long, and the pin plate (equivalent to your metal washer) is 1mm thick. I think extra length of the new washer is supposed to make up for the space the metal washer used to take.

Originally Posted by rosefarts View Post
Of course I tried this first. Depending on the valve, it kinda worked but I lost a lot of air from the threads.

My 3 year old has guaranteed that I can never quite find what I need. No roll of teflon tape but a little sliver on a hose fitting I'm not using now. I used that and it improved the seal. On one wheel, it was perfect and on the other, it was okay. The air loss is coming from around the valve now, not the threads in the head.

Unfortunately, I have to change how far it's screwed for each valve or I'd silicone it in.
This doesn't sound right to me. The inside of the rubber is supposed to seal against the valve, and the outside of the rubber should be sealed against the inside of the pump head bore. No air should be getting to the threads and there shouldn't be any adjusting necessary from valve to valve. The seal may be a little undersized for easy installation, allowing leakage on the outside, but when you actuate the lever to compress the rubber, that should swell it up enough to seal. Any variation from valve to valve should only affect how much drag you have on the rubber as you put the chuck on, but that difference is taken up in the rubber's compliance when you actuate the clamp lever to get the proper seal, .
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