At my wits end with needle valves

I posted before about my needle valves becoming sticky after a few months. Things have become worse, my needle valves become sticky after just one operating session now. It is at the point the valves have to be changed everytime I want to run the tractor which is a 1946 Farmall model A with a Zenith carburetor. There has to be ethanol proof needle valves for old iron out there somewhere? I don't know if they upped the ethanol contant of the local gas sold around me or what, but I just can't keep buying new needle valves every time.

I just don't know what to do? I hate have to stop using my A and get somthing more modern, but I guess big G and big corn or doing there best to force me to that. I don't care about politics, I just want a needle valve that doesn't start sticking right away, even if I have to downgrade to steel tip I will. Help save this A from the scrapyard.

Can you shut off the fuel each time you are going to park it for awhile and let the tractor run until the carburetor is empty? Then the needle valve will not be in the sticking position....

Don't forget to turn off the ignition after it stops!

Good idea by Roger. If ya need to, put a ball valve inline after the bowl if there is one and shut it down so all the fuel is used up by the engine. That varnish leftover is a pain.

Take one of the old sticky needles along with a 3 inch chunk of 3/16" brass rod to a local Technical school and ask them to make you one out of the stock. Interesting real world application for the school. (if it was made with CNC on a mill/turn center, they could make hundreds to sell)! Jim

Sticky leaks after engine is stopped or it wont open. They can be a pain some say when replacing to give it a lite tap to seat it for shut-off it has worked for me If im not going to br uding tractor for a while i let the carb run dry aftr shutting off the fuel at the tank.

GO TO LOCAL MOWER SHOP AND GET A BRIGGS AND STRATTON RUBBER TIP VALVE. THIS WILL SOLVE THE PROBLEM. USED LOTS OF THEM IN RESTORE. WILL NOT STICK IN SEAT.

First I worked on small engines for years (also worked at IH dealer when I was a young guy) and all the small engine manufacturers have shown proof that ethanol is bad news. Causes all kinds of problems. Plus the fact that you loose 20% of power since ethanol burns cooler. I have a farm and a 300 that sets there a lot until I get up there to use it. I will NOT use ethanol in it or my pickup. I only use unleaded or the 87 octane fuel. I have also found that the Briggs and Stratton fuel stabilizer is EXCELLENT stuff!!! It helps to prevent the gumming you are talking about and keeps fuel fresh. Fuel is already about 30 days old by the time you get it. Fuel is only good for 90 days. This stabilizer will help keep it fresh until that time and possible a little longer. I always use a little more than is recommended on the stabilizer bottle. So you might try this method and see if it works for you like it does for me. By the way my truck, a Dodge Dakota, the best it gets is 16 to 17 with ethanol and with regular it will get 18 to 20.

Thanks for the replies. I always close the fuel shut off valve under the tank. But it seems viton tipped needle valves start sticking closed not after much use. Ascsoon as the engine comes under load it hunts and surges and the bumper spring and idle mixture screws don't cure it. Replacing the needle valve stops the hunting and surging for awhile until the new valve starts to stick.

Would a needle for a Marvel carb fit in a Zenith's seat? A few places online sell brass needles for Marvel carbs.

It's not the ethanol causing the problem, thousands of tractors run E10 every day in Iowa. I have 5 engines that sat all winter in the shed, November through April, they all started like they had been run yesterday, I do shut the fuel off and let the carb run dry before I park them for the winter. If I am using them daily I leave the fuel on.

It might be a fuel problem, but not because of the ethanol in the fuel.

Nate

Get rid of the rubber tip, go with a solid needle. You have already heard to run it dry at shut down.
One of the best tricks I have learned is, polish the three sides of the needle with a fine cut file or emery cloth.
The made in Chine parts are just not smooth enough and the seat grabs the needle. (note to newbies,I am talking about the three points not the flat sides of the needle.)
The only way to buy ethanol free gas in this state, is buy Premium gas, and then the only way to know for sure is ask the truck driver who is delivering the gas as it can vary from one station to another, in the same chain.

You must no be using the little wire clip that attaches to the float so when the float drops the needle will open. Where are you getting parts. Ive been using the 10% blend for like 40yrs since its been here in IOWA i have several As and Bs with Zenith carbs and sure dont have the problems you do engines even set all winter in dirt floor shed and they will start in spring but they are in shape with good starting systems still on 6v just dont see why people have trouble then blame the gas. When i had a place in Colo at 10,000 ft near Gunnison tractor would start every spring after setting there all winter.

Correct rest of the system isnt up to snuff so blame the gas. Got to remember the whole system needs to be up to par for good staring and running but its too easy to blame the gas. Just picked up a B that sat all winter started rite up and ran. He wanted it serviced for summer use and cooling system flushed new gen belt and just regular service still on 6v original system with cut-out i did rebuild the gen few yrs ago but he wants to make sure every thing is in shape. Afterall tractor is only60pluss yrs old so why wouldnt you want things in shape so it will do its job when you need it.

With that added symptom, I am going to suggest that a needle valve makes little difference in surging. What will make a difference is mixture. Richer at higher load will cure that. IIRC that carb does not have an adjustable screw for power richness.
A higher float level (1/16") or a larger jet size are in the right direction. Don't ream out your main jet, purchase a new one and experiment on the old with number drills only very small steps at a time. Tiny increments adjust flow big steps dump gas into the system.
Jim

(quoted from post at 15:15:33 05/17/14) I posted before about my needle valves becoming sticky after a few months. Things have become worse, my needle valves become sticky after just one operating session now. It is at the point the valves have to be changed everytime I want to run the tractor which is a 1946 Farmall model A with a Zenith carburetor. There has to be ethanol proof needle valves for old iron out there somewhere? I don't know if they upped the ethanol contant of the local gas sold around me or what, but I just can't keep buying new needle valves every time.

I just don't know what to do? I hate have to stop using my A and get somthing more modern, but I guess big G and big corn or doing there best to force me to that. I don't care about politics, I just want a needle valve that doesn't start sticking right away, even if I have to downgrade to steel tip I will. Help save this A from the scrapyard.

Click to expand...

I have professionally rebuilt many of those carburetors. I can tell you that for certain, if you install the new needle valve just as it comes out of the box, it WILL STICK. The solution is to thoroughly CLEAN the new needle valve and seat with aerosol carb cleaner BEFORE you install it. I never had a come-back after I learned the cleaning trick.

It seems there is a residue of some sort, left over from the manufacturing process, and gasoline does make it sticky. Get rid of the residue first, and no problems.

You must no be using the little wire clip that attaches to the float so when the float drops the needle will open. Where are you getting parts. Ive been using the 10% blend for like 40yrs since its been here in IOWA i have several As and Bs with Zenith carbs and sure dont have the problems you do engines even set all winter in dirt floor shed and they will start in spring but they are in shape with good starting systems still on 6v just dont see why people have trouble then blame the gas. When i had a place in Colo at 10,000 ft near Gunnison tractor would start every spring after setting there all winter.

Click to expand...

Correct rest of the system isnt up to snuff so blame the gas. Got to remember the whole system needs to be up to par for good staring and running but its too easy to blame the gas. Just picked up a B that sat all winter started rite up and ran. He wanted it serviced for summer use and cooling system flushed new gen belt and just regular service still on 6v original system with cut-out i did rebuild the gen few yrs ago but he wants to make sure every thing is in shape. Afterall tractor is only60pluss yrs old so why wouldnt you want things in shape so it will do its job when you need it.

Click to expand...

I have been using the little wire clips, but with the air horn off the needle stick even with the weight of the floats pulling on it, have to shake it hard to unseat the needle. I have had E10 ruin needle valves in other engines from lawn mower motors to even my Chevy's 305. Thankfully Cliff Ruggles sells E10 proof parts for Qjets but not for tractor or lawn mower carbs.

As for my A, the tank is clean, new fuel strainer and fuel line, and brand new Zenith carburetor. Governor is adjusted correctly. Clean 30 weight oil in the air cleaner, made sure there is no gunk in the oil cap, etc. The A will run fine for a few days after changing the needle valve, then it will slowly start running poorer and poorer as the needle tip quickly degrades and becomes sticky. This is a problem I have seen many, many times. In your cases not having sticking problems with E10, sometines old needle vales that have only been exposed to E0 for a while become hardened and less prone to sticking when exposed to E10 than flesh needle valves.

The A has been upgraded to a 12 volt system with alternator and electronic ignition, new coil, rotor, wires, plugs, and cap. Valve adjustment was checked hot. Timing has been checked. Everything but the float system is okay.

I have tried parts from many different soruces and brands and they all stick. I have checked all my T's and dotted all the I's in the A, everything but the needle valves are up to snuff.

I never had any sticking needle valves until they introduced E10 and now just about every carbed engine I have suffers from it except for my Chevy 305 with a high end viton needle valve upgrade. Sadly every station in NJ only sells E10 by state mandate, probably to force us to buy new equipment and the state gets more sales tax.

My A starts up fine, it is at high revs or under load it starts giving me trouble unless it has a flesh needle valve just installed, then it runs under full load without skipping a beat until the valve degrades again, then it starts acting up again. I live in NJ and the gas here may be different than the gas in Iowa, a few stations here have been caught selling E20 labeled as E10, perhaps I should try out of state gas from PA?


Just to be clear, I have checked out everything and everything checks out except the needle valve. The tractor does run fine with a fleah valve installed, but after a few days the valves become sticky and the tractor surges under load. Replace the needle valve and it runs perfectly again. Trust me it is the needle valves degrading quickly because of the current E10 gas. Lots of people have had trouble with E10 from boats, to classic cars, to lawn mowers, to even classic tractors. What I need is a Zenith type needle valve that can stand up to E10 without sticking, pure and simple. I wish this wasn't the case but it is. No one seems to sell all brass or all metal needle valves, everyone only sells viton tipped valves and they all aren't very good viton like they sell for Qjets. I have been fighting this problem for 5 years now ever since the corn juice showed up.

I have professionally rebuilt many of those carburetors. I can tell you that for certain, if you install the new needle valve just as it comes out of the box, it WILL STICK. The solution is to thoroughly CLEAN the new needle valve and seat with aerosol carb cleaner BEFORE you install it. I never had a come-back after I learned the cleaning trick.

It seems there is a residue of some sort, left over from the manufacturing process, and gasoline does make it sticky. Get rid of the residue first, and no problems.

Click to expand...

Can a needle valve still be cleaned of this residue after already being exposed to gas? I guess this residue is some sort of mold release agent for the viton tip. Just spray the tip with carb cleaner and maybe brush it with a tooth brush? thanks. [/quote]

This problem is going to get worse.
Import parts just have to 'look' right.
My guess is they are just using plain old rubber for the tip,
instead of 'viton' or whatever.
Rubber swells with the new gas or additives.
(same with import points with a cheap plastic rubbing block instead of the old time tough as nails material)

I scavenge metal needles out of junk small engine carbs.
Even if the design isn't exactly the same, if they are the right dimensions, I use them. After all, it's just a cone shaped end that gets jammed in the seat.
Like the other poster, I polish the end of used ones before I use them.

......I have been fighting this problem for 5 years now ever since the corn juice showed up.[/quote]

Ethanol or corn juice as you call it has been in gasoline much longer than 5 years. Since your problem is recent (5 years) I would expect another cause/causes rather than simply ethanol.

You've got nothing to lose by trying to clean a needle and re-use it. I bet you can pull the carb and have it torn down in about 10 minutes now, so other than the frustration factor it should be an easy thing to try.

Believe me it's not the ethanol. It's the needles themselves.

Does the needle tip feel sticky at all when you remove it? I bet it doesn't. Wipe it off and it's dry and smooth. The ethanol isn't touching it.

The d*mn things stick fresh out of the package!!! I know all about it.

I don't know whose idea these rubber/viton tipped needles were, but the old all-brass needles worked much much better.

(quoted from post at 21:35:13 05/18/14)

I have professionally rebuilt many of those carburetors. I can tell you that for certain, if you install the new needle valve just as it comes out of the box, it WILL STICK. The solution is to thoroughly CLEAN the new needle valve and seat with aerosol carb cleaner BEFORE you install it. I never had a come-back after I learned the cleaning trick.

It seems there is a residue of some sort, left over from the manufacturing process, and gasoline does make it sticky. Get rid of the residue first, and no problems.

Click to expand...

Can a needle valve still be cleaned of this residue after already being exposed to gas? I guess this residue is some sort of mold release agent for the viton tip. Just spray the tip with carb cleaner and maybe brush it with a tooth brush? thanks.

Click to expand...

/quote]

Yes, you can still clean it, but do NOT use a tooth brush or anything else like that. Just spray it liberally with carb cleaner and either blow it dry with compressed air or just lay it on a clean shop towel and let it dry.

Might also want to make sure you don't still have some old, varnished up gasoline in the tank, and make sure the gasoline you add to the tank is also clean and fresh.

I've been using the ethanol blended gasoline ever since it was introduced in the late '70s, early '80s, and I use it in everything I own. Ethanol is the best thing that ever happened for these old tractors. If it caused problems, I would not use it.

It was introduced into my state 5 years ago to both much fanfare and stink. I know it's been around much longer than that. My late grandfather drove down to VA one time, had to fill up on E10 as that was the only stuff they sold and it caused his car's cat converter to fill up with water and block the exhaust. After he drained the E10 gas and the water out of the car and put E0 back in, it ran fine again and never had the weird water problem again with it.

I don't doubt the newer valves are cheap grade junk either. E10 is not kind to Chinese parts. The rubber tipped needle valves are supposed to last longer than metal tipped ones since any kind of shock or joult wears the all metal ones. However, whatever it is about modern gas it is damaging the rubber tips besides the low quality of the valves themselves, and it seems only high grade viton lasts.

(quoted from post at 07:49:50 05/19/14)
It was introduced into my state 5 years ago to both much fanfare and stink. I know it's been around much longer than that. My late grandfather drove down to VA one time, had to fill up on E10 as that was the only stuff they sold and it caused his car's cat converter to fill up with water and block the exhaust. After he drained the E10 gas and the water out of the car and put E0 back in, it ran fine again and never had the weird water problem again with it.

I don't doubt the newer valves are cheap grade junk either. E10 is not kind to Chinese parts. The rubber tipped needle valves are supposed to last longer than metal tipped ones since any kind of shock or joult wears the all metal ones. However, whatever it is about modern gas it is damaging the rubber tips besides the low quality of the valves themselves, and it seems only high grade viton lasts.

Click to expand...

WHERE oh where did you get all of that false information?

The only thing that would destroy a cat converter back then was leaded gasoline. E10 is UNleaded, so it will never destroy or damage a catalytic convertor. Also, I have personally rebuilt many, many carburetors for the old Farmalls. Most of those carburetors had already been rebuilt at least once and already had the viton tipped needle valve in them. Those tractors had been running for years and years with that rubber tipped valve and the valves were still good. Could have been cleaned up and re-used if had chosen to do so. The original, all steel valves were ALL worn beyond use. I personally own 2 Farmall Hs, and one Farmall M. All 3 tractors see regular use, and I rebuilt all 3 carburetors right after I bought them. ALL 3 have been running on E10 for about 14 to 15 years now, and not a single one has ever given trouble with the fuel system in any shape or fashion.

(quoted from post at 11:22:21 05/19/14)

(quoted from post at 07:49:50 05/19/14)
It was introduced into my state 5 years ago to both much fanfare and stink. I know it's been around much longer than that. My late grandfather drove down to VA one time, had to fill up on E10 as that was the only stuff they sold and it caused his car's cat converter to fill up with water and block the exhaust. After he drained the E10 gas and the water out of the car and put E0 back in, it ran fine again and never had the weird water problem again with it.

I don't doubt the newer valves are cheap grade junk either. E10 is not kind to Chinese parts. The rubber tipped needle valves are supposed to last longer than metal tipped ones since any kind of shock or joult wears the all metal ones. However, whatever it is about modern gas it is damaging the rubber tips besides the low quality of the valves themselves, and it seems only high grade viton lasts.

Click to expand...

WHERE oh where did you get all of that false information?

The only thing that would destroy a cat converter back then was leaded gasoline. E10 is UNleaded, so it will never destroy or damage a catalytic convertor. Also, I have personally rebuilt many, many carburetors for the old Farmalls. Most of those carburetors had already been rebuilt at least once and already had the viton tipped needle valve in them. Those tractors had been running for years and years with that rubber tipped valve and the valves were still good. Could have been cleaned up and re-used if had chosen to do so. The original, all steel valves were ALL worn beyond use. I personally own 2 Farmall Hs, and one Farmall M. All 3 tractors see regular use, and I rebuilt all 3 carburetors right after I bought them. ALL 3 have been running on E10 for about 14 to 15 years now, and not a single one has ever given trouble with the fuel system in any shape or fashion.

Click to expand...

This info came from my late grandfather who was an experienced heavy equipment mechanic who know what he was talking about and wasn't giving out bad info. The cat converter wasn't ruined either, it just filled up with water. He took it off, dumped the water out, let it air dry, bolted it back on after draining the VA E10 gas out of the car's tank, poured in NJ E0 and car ran for years without trouble, never had a repeat of the water forming in the cat agian, just a weird reaction with the VA gas which was E10, had a big corn sticker on the pump. Maybe the gas was water contaminated since E10 absorbs more water than E0.

Back to the Farmall A, I tried cleaning the needle off using carb cleaner. Sprayed it down really well, let it air dry. Put the carb back together, double checked the float height just in case. Bolted the carb back on, opened the fuel valve and the carb flooded immediately. Took the carb back off and took it apart again, the tip turned softer than before and is no longer sealing. I checked the seat and it was clean. Screwed it out and the passage way above it was also clean. New needle valves for old tractors are crap now and E10 comnpounds the problem. Harsher fuel with weaker parts leads to bad times. I need to find better parts and better gas. Looks like I will have to have custom brass needle valves made.

The Viton tipped needle showed up on IH tractors some time after the introduction of the 4 & 560 model gasoline tractors. The new tractors were standing in the show rooms and lots dripping gasoline from carb. Some blamed it onto larger fuel tanks, others on minute particles in the gasoline , at any rate the Viton tip took care of the problem. About the time CASEIH came on the scene, parts started to give trouble and have ever since. I have had better luck with the latest ones again though. Seems they might have finally corrected some of the poor quality. Even the seat is egg shaped in some of them which I coin with a tip of an injection nozzle that is the correct taper. And, cleaning the new needle gets the varnish or what ever it comes with off.

According to the CASE/IH parts website, they don't sell needle valves for As anymore.

All I know is you've got some seriously bad gas.

I have soaked viton-tipped needles in straight Everclear, which is 95% ethanol, and nothing happens to them.

Just yesterday, I got out my Cub Cadet 4-stroke string trimmer for the first time since October.

It still had half a tank of 8 month old gas in it. No Sta-Bil. No 2-stroke oil. Just plain 87 octane pump gas with 10% ethanol.

I took the cap off and stuck my nose in. Smelled like gas. Put the cap back on.

Hit the priming bulb 10 times like it says on the shroud. Pulled the starter twice. VROOOOOOOOM! Ran like a top.

(quoted from post at 04:56:33 05/20/14) All I know is you've got some seriously bad gas.

I have soaked viton-tipped needles in straight Everclear, which is 95% ethanol, and nothing happens to them.

Just yesterday, I got out my Cub Cadet 4-stroke string trimmer for the first time since October.

It still had half a tank of 8 month old gas in it. No Sta-Bil. No 2-stroke oil. Just plain 87 octane pump gas with 10% ethanol.

I took the cap off and stuck my nose in. Smelled like gas. Put the cap back on.

Hit the priming bulb 10 times like it says on the shroud. Pulled the starter twice. VROOOOOOOOM! Ran like a top.

Click to expand...

I think it is both bad gas and bad needle valves that can't take it. Over the winter I have to drain the gas out of my stuff because the ethanol phase separates in the fuel tanks with open venting otherwise. I know this from experience. Doesn't do it in the gas can when sealed up tight. I am using the triple baffle safety gas cap if that makes a diffference? However the new needle valves are pretty lousy since they can't take carb cleaner without failing.

(quoted from post at 05:57:21 05/20/14)

(quoted from post at 04:56:33 05/20/14) All I know is you've got some seriously bad gas.

I have soaked viton-tipped needles in straight Everclear, which is 95% ethanol, and nothing happens to them.

Just yesterday, I got out my Cub Cadet 4-stroke string trimmer for the first time since October.

It still had half a tank of 8 month old gas in it. No Sta-Bil. No 2-stroke oil. Just plain 87 octane pump gas with 10% ethanol.

I took the cap off and stuck my nose in. Smelled like gas. Put the cap back on.

Hit the priming bulb 10 times like it says on the shroud. Pulled the starter twice. VROOOOOOOOM! Ran like a top.

Click to expand...

I think it is both bad gas and bad needle valves that can't take it. Over the winter I have to drain the gas out of my stuff because the ethanol phase separates in the fuel tanks with open venting otherwise. I know this from experience. Doesn't do it in the gas can when sealed up tight. I am using the triple baffle safety gas cap if that makes a diffference? However the new needle valves are pretty lousy since they can't take carb cleaner without failing.

Click to expand...

I am 63 years old. I've been mechanicing on cars, trucks, and tractors since I was 16. Many others on this forum are similarly experienced, and several of them have also offered advice to cure your fuel problems, but still you argue with us. I'll be quiet now.

(quoted from post at 06:38:24 05/20/14)

(quoted from post at 05:57:21 05/20/14)

(quoted from post at 04:56:33 05/20/14) All I know is you've got some seriously bad gas.

I have soaked viton-tipped needles in straight Everclear, which is 95% ethanol, and nothing happens to them.

Just yesterday, I got out my Cub Cadet 4-stroke string trimmer for the first time since October.

It still had half a tank of 8 month old gas in it. No Sta-Bil. No 2-stroke oil. Just plain 87 octane pump gas with 10% ethanol.

I took the cap off and stuck my nose in. Smelled like gas. Put the cap back on.

Hit the priming bulb 10 times like it says on the shroud. Pulled the starter twice. VROOOOOOOOM! Ran like a top.

Click to expand...

I think it is both bad gas and bad needle valves that can't take it. Over the winter I have to drain the gas out of my stuff because the ethanol phase separates in the fuel tanks with open venting otherwise. I know this from experience. Doesn't do it in the gas can when sealed up tight. I am using the triple baffle safety gas cap if that makes a diffference? However the new needle valves are pretty lousy since they can't take carb cleaner without failing.

Click to expand...

I am 63 years old. I've been mechanicing on cars, trucks, and tractors since I was 16. Many others on this forum are similarly experienced, and several of them have also offered advice to cure your fuel problems, but still you argue with us. I'll be quiet now.

Click to expand...

Not trying to argue with you or anyone else. I am just relating my experiences and situation which must be different form yours. I am sorry you must feel that way but sticking your head in the sand won't solve anything. But this is what happened the other times I asked about this problem on this forum, kept getting the run arounds until some people started to get sore headed and denying problems. E10 can and has caused problems for some people, just be glad it has caused trouble for you.

I double checked to see where my needle valve that failed was made, it's package says it is a USA made part. I guess US workmen ship isn't what it used to be. :shock: Now the question is where can I get a decent needle valve that can withstand modern gas. A well made needle valve should handle modern E10 without issue, but it seems no one bothers to make decent needle valves for Farmalls, not even CASE/IH. If you don't like that then blame CASE/IH, not me, you are just trying to blame the victim.

Looking around online, it seems no one is offering brass needle valves or viton needle valves for Zenith carburetors. For Marvel carburetors, several places sell brass needle valves and needle valves labeled viton tipped. I guess if a needle valve isn't labeled viton, then it's probably just rubber tipped. In which case, no one is offering Zenith needle valves labeled viton which probably means they only make rubber tip valves for Zenith. Looks like I may have to swap from a Zenith to a Marvel carburetor since Marvels have ethanol proof parts available for them and Zeniths don't.

Not that anybody cares it seems, sigh.

It's not that nobody cares, so cancel the pity party.

Frankly I cannot say that I have EVER heard of anyone having a problem even remotely similar to yours. I've been around tractors all my life, and on this forum for over 10 years, and I have never come across needle valves literally turning gooey in the presence of carburetor cleaner.

Last year I bought a cheap Tisco kit for the Zenith carb on my Super A. I have the opposite problem as you. Mine doesn't seal 100% and will develop a slow drip if I leave the gas valve on.

Again, I've been using ethanol fuel since it came out here probably close to 15 years ago. Not a single problem. Nothing plastic, rubber, viton, or whatever has melted or even softened. I have chainsaws and mowers and weed wackers and tractors that sit for months with untreated gas in them, and they start right up. Your foot-stomping insistence that it *HAS* to be the ethanol has me scratching my head as much as your problem does.

Something is going on, I have had new lawm mowers and a snow thrower develop flooding problems in a year. With my searching online I have seen other classic tractors owners complain about sticking needle valves that they have to change often, so I am not the only one with this problem.

In the classic car scene they do offer viton carburetor parts to replace rubber carburetor parts. They even warn to avoid older rebuild kits that still have rubber instead of viton. My Chevy with a 4bbl 305 runs on the same gas and thankfully doesn't suffer this sticking or leaking problems but is has good viton replacement parts in the carb. I have seen pictures of brand new accelerator melting in a hour in a glass of E10.

Again looking around online, it seems no one lists needle valves for Zenith carburetors as having viton tips like they do with Marvel carbs. For Marvel carburetors they do list needle valves for them as having viton tips. This has me thinking that new Zenith needle valves are just rubber tipped and not viton, viton usually has a blue tint that I don't see on Zenith needle valves.

I can't believe that carb cleaner ruined a needle valve either, maybe because it was already damaged by the gas? It was regular old Gumout which never did anything like this before. It should not have happened but it did, this indicates that the part must be low quality, US made or not. Maybe it's just a bad batch of Zenith needle valves floating around in the market, who knows. What I do is is that there is one tiny but critical part that is just not holding up and that I am having a hard time finding a quality replacement.

SEEMS YOU STILL HAVE A MAJOR PROBLEM. I WOULD LIKE TO SUGGEST THAT YOU GET YOU A CLEAN METAL GAS CAN,TAKE TO SOMEONE AND HAVE A CONNECTION SOLDERED IN THE BOTTOM OF CAN, CONNECT A RUBBER TEMP HOSE FROM THE CAN DIRECTLY TO THE CARB WHEN YOU INSTALL A NEW VALVE. FILL WITH SAME FUEL YOU CURRENTLY USE, AND LET SET A FEW DAYS. SEE IF YOU HAVE THE SAME PROBLEM WITH THE TEMP GAS TANK CONVERSION. IF EVERYTHING OK, WOULD SUGGEST YOU FIND ANOTHER TANK FOR YOUR TRACTOR. ON LOTS OF RESTORES, IF REGULAR GASOLINE OR TRACTOR FUELS SET FOR ANY LENGTH OF TIME, THEY WILL PRODUCE AN OILY AND TAR FILM IN THE BOTTOM OF TANK.; NOTHING WILL REMOVE THIS FILM FROM THE OLD TANK. I HAVE DONE MANY RESTORES THAT SET FOR YEARS, AND FIND LOTS OF THEM WITH TAR BUILDUPS AS MUCH AS ONE INCH OR MORE THICK. I HAVE EVEN REMOVED THE TANKS FROM THE OLD TRACTORS, TURNED UPSIDE DOWN ON A BRUSH PILE, AND MELTED OUT THE TAR ADDATIVES, THEN PUT A LIQUID LINER IN TO SEAL ALL THE PITS AND RUST THAT OCCOURED FROM THE HEAT.(DO NOT ADVISE THIS),BUT HAVE DID LOTS THIS WAY.

ALSO, WHEN YOU ARE CHANGING THE NEEDLE VALVE, ARE YOU CHANGING THE SEAT ALSO. THE PROBLEM MAY BE SIMPLY WITH YOUR SEAT. GET NEW VALVE AND SEAT AND INSTALL BOTH. I HAVE THIS PROBLEM MANY TIMES SIMILAR TO YOURS, BUT FIND THAT THERE IS NOTHING WRONG WITH THE FUEL. IT IS A SIMPLE PROBLEM THAT YOU ARE MISSING. ALSO, THIS TYPE CARB HAS AN ELBOW THAT SCREWS IN WHERE THE GAS LINE CONNECTS,BEHIND THIS ELBOW,THERE IS A SCREEN MADE ON THE ELL FROM THE FACTORY, THAT MAY BE TOTALLY CLOGGED WITH THE OILY SUBS THAT YOU ARE GETTING, AND AS FUEL PASSES THRU, WILL DEFINETLY STICK THE NEEDLE. MOST EVERYONE NEVER REMOVES THE ELBOW, JUST THE GAS LINE THAT SCREWS TO THE CARB.