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Rebuilding carb stix & a question for old timers about same. 20 Mar 2024 19:03 #896686

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We've had a set of ancient Vance & Hines mercury carb stix for decades.




  The four silicone rubber vacuum tubes have been removed in the both pics, and the back cover removed from the housing to show the bottom reservoir & tops of the capillary tubes sans rubber tubes.

The past few years we've been seeing occasional, random air bubbles / voids in the mercury columns.
The voids run anywhere from 2 to 4 mm long.  They can appear in different positions in the column if vacuum is removed & reapplied.  Or not at all.  Occasionally there may be two voids in a column.  It's very random.  The reservoir is full to the top & the vent is unobstructed. We decided to clean & rebuild.

Drained the reservoir & filtered the merc through a tiny hole in a paper filter, a method we found researching how to clean a small quantity of merc.  We did so because a layer of oxidation that looks like slag sat on top of the merc. The paper caught the layer of  oxidation  & held it on the sides of the paper filter while clean, shiny liquid merc dropped into the glass storage vial.  The  glass lab vial, capped & set aside.  It's about 2 fl.oz., or 59ml. In volume.

Removed the cap from the reservoir, and the capillary tubes from the cap.  Cleaned the inside of the reservoir tub and the outside of the capillary tubes.

Capillary passages themselves appeared clean, which is a good thing.  At about 0.025”, or 0.635mm, we'd have no way to clean the minuscule passages, and they're capped at the top with some sort of porous sealant anyway.  More on that later.

Reassembled & resealed the cap to the reservoir tub with a two part adhesive suitable for polyethylene.  Reinsert the tubes evenly into the reservoir cap & seal with blue RTV.  Inserted the tube/reservoir assembly into the housing. Pressed the silicone vacuum tubes onto the top of the capillary tubes after warming them to soften.  Refilled the reservoir with the cleaned merc using a pipette to introduce it into the vertical vent tube a tiny portion at a time.  Tedious.  Test for vacuum leaks with a vacuum pump set to hold vacuum to make sure there were no vacuum leaks.  No voids were seen.  Vacuum held constant on all 4 tubes.

Bag & take everything that touched merc to the local HazMat disposal site.

Done.

All work was done safely & cleanly as possible outdoors wearing nitrile gloves.   There were no spills or gottaway beads.

A curiosity question for the old-timers:
When we removed the silicone rubber vacuum tubes from the tops of the glass capillary tubes we noticed white material of some sort covering the top 10mm or so of each tube.  It's quite hard & very well adhered to the glass itself.  Won't scratch with a fingernail.  Seems ceramic-like. It has to be porous, because it flows air.  Otherwise no mercury could be drawn into the capillaries by vacuum.


Out best guess is, it's there to keep mercury from being drawn out the top of the tubes.  We're not gonna attempt to remove it, but we're curious; anyone know what the white material is?

Good Ridin'
slmjim & Z1BEBE
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1972 Z1 x2
1974 Z1-A x2
1975 Z1-B x2
1993 CB 750 Nighthawk x2
2009 ST1300A

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Rebuilding carb stix & a question for old timers about same. 21 Mar 2024 09:19 #896700

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So, the flexible hoses slide over the top of that white stuff on top of the capillary tubes?  Assuming yes, I think that white stuff serves two purposes:  One, as you reference, it reduces the chance of spilling, and two, it works as a restrictor, to reduce pressure pulses that cause the mercury column to oscillate.  

Back in the day, I made my own mercury manometer for balancing carbs.   A few ounces of mercury, some glass capillary tubes, and a rack to hold it all together.  Great fun.  
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Rebuilding carb stix & a question for old timers about same. 21 Mar 2024 11:03 #896706

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I would like to hear how your column works after this rebuild.

I believe I need to do the same to mine as I have that "streaking" issue when I use it. Its not a V&H unit, some off brand named PCCC bought it at a local motorcycle dealership 40 years ago.



Mine has a simple rubber plug vent.

I suspect those white caps were probably made out of a porous foam that has hardened over time. Lab pipettes have a white filter in them similar to a cigarette filter, maybe the same material was used for those caps and somehow reacted to the mercury vapors.


 
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Rebuilding carb stix & a question for old timers about same. 21 Mar 2024 18:31 #896721

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We have a bright yellow, 4-pipe PCCC set of vacuum stix we got from the same bike shop as the mystery 4 - 2 system we posted about elsewhere on KZR.  They're likely going to the Mid-Ohio swap meet this year.  We don't like the black rubber tubing that came on it, because they're too short for our liking, but that could be easily remedied.  The merc reservoir is full.  Haven't tested them ourselves, but the guy likely used them often when he was healthy.

The V&H set we rebuilt fluttered something fierce when we got it pre-owned decades ago.  There were supposed to be adjustable restrictors on the rubber tubing, but they and all the screw-in adapters were missing.  We replaced the four rubber tubes with fresh silicone tubing some years ago, and solved the fluttering problem by inserting a VM28SS pilot jet in the motor end of each one.  The tiny orifice damps fluttering very effectively.  We just got the final assembly completed today.  We're prepping one of our '74 Z1-A's to Ride this year for it's 50th. birthday & will be using them to adjust sync after we cleaned the carbs over the winter.  We'll update results soon.

Suppose those white caps could have been foam at one time.  They're so hard & firmly adhered to the glass it seems they were fired on with heat.  They may remain a mystery.

Good Ridin'
slmjim & Z1BEBE
A biker looks at your engine and chrome.
A Rider looks at your odometer and tags.

1972 Z1 x2
1974 Z1-A x2
1975 Z1-B x2
1993 CB 750 Nighthawk x2
2009 ST1300A

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An enthusiast's forum focused exclusively
on all things Z1, Z2 and KZ900.

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Rebuilding carb stix & a question for old timers about same. 22 Mar 2024 20:31 #896765

  • Cra-z1
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Just make your own. If you can get a bit more mercury it is an option. Im extremely careful with the mercury as the bottle is open to the atmosphere when in use but has a cover when not. Im the only one who I trust when using them. You could get fancy and have the tubes go through a rubber cap a guess but you still need to have it open to the atmosphere . My tubes are 1/16 ID I believe. I run restricters in the tubes. I use restricters that came with a set of the newer Motion Pro units that ran that blue fluid that doesn't work that well. they are just a small piece of plastic with very tiny holes drilled through them. The tubes lift up and  I insert the bottle and lower the tubes into the mercury. This is the second set I made probably 12 years ago. Haven't spilled any mercury yet. The first set was in the 70's when mercury was readily available. I worked as a commercial HVAC tech and the mercury came from quite a few Honeywell T-stats that were replaced with digital unit.  I have tied all the other sync devices but the mercury units have been the best. I haven't tried Digi Sync and that may be a non mercury option.

<iframe src="player.vimeo.com/video/912358205?h=982faed7d0" width="640" height="1138" frameborder="0" allow="autoplay; fullscreen; picture-in-picture" allowfullscreen>
<p><a href="vimeo.com/912358205">sync 19 from vimeo.com/user209920359">Wayne Passow on vimeo.com">Vimeo.

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