Zenith over flow
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=209938
Printed Date: 21 Mar 2026 at 6:13pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: Zenith over flow
Posted By: 3rd generation
Subject: Zenith over flow
Date Posted: 01 Feb 2026 at 1:39pm
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Allis C. I’ve tried it all. Carb has been cleaned with Berryman cleaner. The body also soaked in evaporust. Added inline fuel filter. Float height is good and floats do not hang up on side wall. New gasket under float needle seat body. I even removed the wire clip between the float and float needle. Tried different needles. Only thing left is buy several needles and seats in hopes I get a good match. I’ve read the aftermarket carbs have poor performance. Is a Marvel carb an option? |
Replies:
Posted By: HudCo
Date Posted: 01 Feb 2026 at 2:24pm
| does the float leak? boil it to see if it bubbles or hisses |
Posted By: 3rd generation
Date Posted: 01 Feb 2026 at 2:34pm
| No I checked that also. If I blow into an empty carb bowl it holds holding upside down. As soon as it overflows I disconnect fuel line from carb and attach a hose and blow it appears to hold but under gravity feed it overflows as soon as the bowl fills up with fuel valve open. I measured the original needle to be a few thousands larger than the new needle thinking it gets kicked to side of dead center into seat hole. Sad because this tractor has been completely taken apart and overhauled from lower drive to engine. |
Posted By: Les Kerf
Date Posted: 01 Feb 2026 at 3:41pm
Methinks the float doesn't float enough
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3rd generation wrote:Posted By: steve(ill)
Date Posted: 01 Feb 2026 at 4:31pm
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if you have tried several needles and they all leak, then i would lower the float like Les said.. ------------- Like them all, but love the "B"s. |
Posted By: Skip, W.Pa
Date Posted: 01 Feb 2026 at 7:59pm
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I have had problems with the main jet discharge tube gasket leaking. Some were not tight enough and leaked at the round gasket under shoulder. Some the gasket dried out from sitting extended period with no fuel in carburetor. Makes you think it is a needle seat / float issue. When it leaks gas will wick it's way up past gasket and drip out the bottom of carburetor when tractor sits for period of time. Something to look at when you take carb apart. |
Posted By: HudCo
Date Posted: 01 Feb 2026 at 9:30pm
| what skip said set just the bowl level with the nozzle in and carfully and slowly fill it with gas and see if their is leaks bottom of those bowls can crack if they have had water in it and froze , but the nozzleis probley leaking at that gasket, 0if the float is good and the seat is polished |
Posted By: DanielW
Date Posted: 02 Feb 2026 at 7:22am
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What needle came with the latest carb kit? If it has a soft/urethane tip, they typically seal well no matter what (as long as the float's not rubbing and set correctly). But if it's a solid brass needle (which I think the original would have had) they are often difficult to get to seal fully. 'Proper' practice for a solid brass needle & seat is to place the needle in the seat and very lightly tap it into the seat with a small hammer, turning it slowly between taps, to get a full face seal. Though admittedly the machining tolerances these days are 'usually' good enough that it's seldom necessary. But if having trouble, that's where I'd start. Also make sure the faces between both halves of the carb bowl are uber-clean and flat, with the proper gasket on there. An air leak around there can cause some funky leaking behavior that doesn't always seem to make sense or be traceable.
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Posted By: Les Kerf
Date Posted: 02 Feb 2026 at 8:18am
Good point
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Posted By: 3rd generation
Date Posted: 02 Feb 2026 at 10:09am
| I watched the gas start to run out the main feed first then shortly it runs out the hole located near top on the air inlet. Regardless the gas should not run out that hole if float is working. Yes I set in vice and filled bowl with gas. I adjusted the float to 1-5/16” vs blood 1/5/32”. Confirmed float working by blowing into fuel inlet while slowly drain gas from bowl. Appears to hold until I install on tractor under normal gravity feed. I waked away to come back and now it’s holding. It acting like the rubber needle needs to swell up. No brads needle. Both needles are rubber tip. |
Posted By: 3rd generation
Date Posted: 02 Feb 2026 at 11:40am
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To be clear. I’m observing the gas overflow with oil bath cleaner off. I’m looking into intake of carb. The gas appears to be coming from upper area of what I believe to be the main jet feed. A cascading effect getting surface wet. In very short time gas runs out hole positioned at about 2 o’clock inside carb intake throat. I’ll admit I have not pulled the long brass tube ( I believe to be main feed) I’ll need a deep well socket for that. I can definitely see that gasket leaking but to have gas rise as high as needed to run out the 2 o’clock hole in intake it must be over filling. Filling bowl with gas does not leak nor does the gasket between two halves. Gas runs out intake throat. |
Posted By: Steve in NJ
Date Posted: 03 Feb 2026 at 8:07am
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Take a piece of super fine steel wool and polish the sides of the needle. I've found over the years of rebuilding customer Carbs that sometimes there may be a rough edge on the needle body and it hangs up the needle in the seat allowing fuel to pass by causing a flooding issue. The Viton tips that are on these needles work great for seating, but the smallest piece of dirt can stick to that tip and allow fuel to pass through. Another thing to do is to use a bore brush and run that brush in and out of the fuel inlet. Carburetors with age on them have a lot of crap accumulate in that inlet cavity. You wouldn't believe the rust and debris that comes out of that cavity even after soaking the Carb and glass beading. Rust and debris get stuck in the inlet threads and at the back of the cavity allowing rust and debris to keep causing havoc with the needle n' seat as fuel rolls through that cavity. I've had a pile of rust on the assembly bench from some Carbs after running the bore brush in them with an electric drill. It's amazing what comes outta there! HTH Steve@B&B ------------- 39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife |
Posted By: 3rd generation
Date Posted: 03 Feb 2026 at 9:18pm
| Thanks to all. As of late the carb is not leaking. Yes and yes to all that mentioned suggestions. I’m not disagreeing it’s just I have cared for this carb almost to a NASA level of cleanliness. I Carefully examined the needle rubber tip under microscope. Used dental pick to clean debris from input threads after a long soak in evaporust. In line filter etc. I come to believe the rubber tip was too hard and dry. It needed some exposure to gas to soften up. I know this doesn’t add up considering old original needles were solid brass. Currently I still have float set to 1-5/16”. Fortunately I have very level ground to use this tractor with belly mower. Doubtful the ol girl will ask for more gas than what’s in the reduced fuel bowl. |