Zenith Carb Question(s)

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Dick Weiss
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Re: Zenith Carb Question(s)

#46 Post by Dick Weiss » Thu Aug 29, 2019 10:36 pm

Two different things about Zenith carbs;

1. The choke cover screws aren't flat headed--they're slightly crowned.
2. I've had several Zenith choke cover screws w/o star washers and they were lightly "staked"
(w/a screwdriver tip) next to a screw-slot/edge to lock it in position. It still can be R & Rd if needed.

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Ken Tuvman
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Re: Zenith Carb Question(s)

#47 Post by Ken Tuvman » Fri Aug 30, 2019 8:38 am

Bruce Smith wrote:
Thu Aug 29, 2019 7:23 pm
The solution is pretty simple, and I've done a lot of them (hundreds). I usually use Walker kit pumps and have only had a couple that were difficult to seal. First make sure the pump cylinder in the carb housing is clean and smooth. If it's pitted, which is rare, you're going to have problems and probably will need a new body. If needed, run a brass small brush or a some Scotch-brite inside the cylinder but don't overdo it. Clean it and dry it good (no oil, WD-40, etc.) Then expand the skirt of the dry leather sheath of the new pump just a little bit, again don't overdo it. When you insert the pump, guide it squarely into the cylinder to ensure that it goes in evenly all around since you've expanded it's skirt. Insert it dry, i.e. no oil, gas, or solvent. Then do the set-up up on a bench with mineral spirits to adjust float level and pump volume. Wait a few minutes after you've filled the bowl so that the pump sheath is sufficiently wetted. Then manually work the pump through its full stroke with the pump rod disconnected until it begins to squirt from both injectors. Problems can arise if you haven't cleared and gauged the pump jets and injectors, ensured their seats are clean and smooth, and installed new pump jet o-ring seals. Once they're squirting, connect the pump rod to measure volume. A good starting length is 70mm. Longer is less volume shorter is more. I use a syringe to fill the bowls - I wrote a Registry article a while back on the set-up.
Regarding "Expanding the skirt just a little bit - what is the proper "technique" to do this?

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Brian R Adams
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Re: Zenith Carb Question(s)

#48 Post by Brian R Adams » Sun Sep 01, 2019 8:44 pm

Ken Tuvman wrote:
Thu Aug 29, 2019 8:22 pm
Thank You Bruce - would love to see a link to your story and read it.
A simple search for "syringe" brought me to Bruce's post. Substitute a large plastic syringe for my outboard motor priming bulb and filter as a pickup dongle:

viewtopic.php?f=1&t=35783&p=278240&hili ... ge#p278240
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"In God we trust. All others bring data." W. Edwards Deming

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Brian R Adams
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Re: Zenith Carb Question(s)

#49 Post by Brian R Adams » Sun Sep 01, 2019 9:16 pm

In the article Ron LaDow published on refreshing Zeniths he wrote:

"Fit the idle mixture screws (with springs) by hand. Gently; no fresh grooves on your new mixture screws. After you try it two or three times, your fingers will tell you when they stop. If you ‘groove' one, you have spares. Back each of them out 1-1/2 turns from the ‘stop'."

I wanted to avoid bottoming out the mixture screws with the springs in place, as it's too hard to feel them bottom out without going a little too far (the compressed springs make you use force to advance them that last bit.) Without the springs, the screws rattle around in the holes, and allow you to be very sensitive to bottoming out. So ... With springs set aside, I took a new mixture screw and noted the position of the screwdriver slot when I barely engaged the threads in the hole. From there I turned it clockwise 1/2 turn at a time by watching the slot. Counting 1/2 turns, it took 14 (or 7 full turns) plus about ~1/8 turn to bottom out gently. This turn count seems consistent (as expected) across all 4 idle mixture screws/holes.

Now I can put the springs on, get the mixture screw threads just engaged, then add 11 half turns (or 5.5 full turns) without ever bottoming out the screws, and know I am ~1-1/2 turns from "closed". Later, when tuning the idle mixtures, I add or subtract 1/4 turns from the starting position, and, by keeping track, avoid coming near bottoming out, and if I do approach bottomed, I know there's an abnormal rich condition in play that needs to be addressed elsewhere (idle jet, float level, ...) In this way, there's a high likelihood of installing and adjusting the new mixture screws without ever bottoming them out and scoring the conical tips.
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"In God we trust. All others bring data." W. Edwards Deming

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Brian R Adams
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Re: Zenith Carb Question(s)

#50 Post by Brian R Adams » Tue Sep 03, 2019 2:17 pm

Ron LaDow wrote:
Thu Aug 29, 2019 3:36 pm
...
Posting here, as this is the active Zenith thread:

Ron, in 2014 you wrote:

The kits typically include .04" and .05" alum shims and .028" fiber shims. And if you are rebuilding your carbs, hang on to all the shims that you find. Finally, these guys ( http://www.pinzgauer.com/parts.php?cat=pinzgauer&id=3 ) have .02" shims.
Since they all need at least two shims, some mix of this and thats will always get you in spec.


In playing with the loose washers in the kit, and the provided float valves, I notice something bothersome. On the new valve (as on the old) there is a shoulder which centers the included fiber washer perfectly. However, the shoulder is only "tall" enough to center the bottom washer. If I stack another washer on top of it, the second washer is above the shoulder and can float laterally. I see this as a possible issue in preventing any leakage of fuel past the washer stack. The ideal scenario is a single aluminum or copper washer with the proper ID/OD that is the desired thickness.

How do you address keeping the washer stack concentric? Is it just a matter of holding them ~concentric while tightening the valve into the carb top? It occurs to me one could apply a scant film of sealant between the washers and clamp them together, concentric, to dry before final assembly.

PS My Walker kit holds aluminum washers .040" and .060" (not .050") plus the red fiber .028" packaged with the float valve.

PPS Here's the link to the .020" (0,5mm) Ron referenced:

https://swissarmyvehicles.com/pinzgauer ... enith-ndix

They also sell a .040" (1mm) washer:

https://swissarmyvehicles.com/pinzgauer ... enith-ndix

Note: The .040" (1mm) aluminum washer in the Walker kit will work as a shim, but it is intended for the accel. pump pressure valve, and it has a slightly larger ID than it should, so it's a looser fit around the shoulder on the float valve. I happen to have some of the .020" (0,5mm) and 0.040" (1mm) aluminum washers from SWA (see above) and these have smaller IDs for a better fit on the float valve.

Brian
"In God we trust. All others bring data." W. Edwards Deming

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Ken Tuvman
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Re: Zenith Carb Question(s)

#51 Post by Ken Tuvman » Tue Sep 10, 2019 8:56 am

Good Morning - want to try to set the floats using suggestions above - don't have a banjo bolt handy to make a pump like Brian did on post #25

Found these (2) on Ebay - would either of these work?

Thank You
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Brian R Adams
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Re: Zenith Carb Question(s)

#52 Post by Brian R Adams » Tue Sep 10, 2019 2:11 pm

Ken,

I believe they will all work, but I would prefer red fiber washers myself, as (ironically) they don't tend to wear out (work harden, scuff) with repeated cycling. The one example has a 1/8-27 pipe threaded hole in the head for attaching a pressure gauge. I'd rather put the gauge inline (w/ 'T') so I wouldn't have to plug that hole if I omit the gauge. I also don't like the idea of the gauge hanging on the bolt anyway.

Brian
"In God we trust. All others bring data." W. Edwards Deming

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