What does gas seepage around carburetor gasket mean?

lastcowboy32

Well-known Member
Frequent flyer here lately. My apologies.

Anyway. I rebuilt the carburetor on my 2N. Before the rebuild, I could unscrew my main jet all of the way out, and the engine would still run. I was told that, that particular symptom pointed toward a plugged bowl vent within the carburetor. So, I disassembled the carb, cleaned it all out with carburetor cleaner and installed all new parts from a kit.

The engine does run better, and it now runs too rich and stalls out when I unscrew the main jet all of the way.

BUT...

I've noticed a little bit of dampness on the lower half of my carburetor after I run the tractor for an hour or so. It smells like gas.

I know that it isn't the screws that hold the carburetor together. I specifically remember tightening them down hard with a screwdriver.

Some possibilities in my mind, please let me know if these are plausible or if I'm missing a possible cause:

1. When I cleaned the carburetor out, I noticed that the gasket mating surface (the surface between the two halves) seemed to have some kind of sealer on it. The carburetor cleaner softened it up, and I scraped it off with a plastic putty knife. I reassembled with no sealer. I figured that a cardboard gasket wouldn't need it. Am I wrong here? Or maybe I just need to look at that surface again. Maybe the plastic putty knife didn't clean it well enough. The bowl seems like cast iron. It should be able to take a steel putty knife, shouldn't it?

2. Stuck float? But jeez, the kit came with a new float valve that I specifically remember putting in, and my float was at least 1/4" above the gasket when resting upside down (as my FO-4 manual said that it should be), and I installed a new pivot pin for the float from the kit.

3. This tractor did have a stuck valve that I recently loosened up. Could this valve still be partially sticking or intermittently sticking; which would cause the compression stroke in that cylinder to blow fuel/air back down the intake manifold at the carburetor?

I turn the gas off at the bottom of the tank when I put the tractor up for the night. I could possibly check into the stuck float theory by waiting for the outside of the carb to dry out and just turn the gas back on without running the tractor...if I see seepage then; it seems that my float valve must not be working, right? If that isn't the case; then I could check the other theories?
 

I was just thinking.

Float could be fine, but the fuel could be splashing around in the bowl when the tractor goes over bumps, and the gasket just isn't sealing that very well?

It's some kind of a cardboard/fiber gasket, when it's new, does it need to (like a cork gasket) get wet after some use to really seal up the way that it should?
 
in general, the fiber gasket is perfectly fine. if your mating surfaces are pitted, you COULD use a sealer.. but using sealer means you cant take the carb apart for a looksee without destroying the gasket.

float could still be set too high, or the needle seat may be leaking due to bad fit or under the seat.

not uncommon to get moisture on some parts of a carb.. moisture and a drop of gas is going to smell like gas.

or it could be leaking as mentioned and really be gas.

check inlet too.
 

Thanks,

It doesn't seem to bother anything. It seems that I notice everything now.

I'll just observe for a day or two, especially to see if it wets up if I just turn the gas on without running the engine.

I should also say that, the last thing that I was doing last night before I put it up and looked at it was tuning the high jet on the carb by starting in high gear on the level and going up a short, steep hill and rolling back down then turning the needle by 1/8 turn increments to find a setting where it took the loading the best.

It was in incline, it was bumpy...probably splashing gas around in the bowl a lot.
 
I had the same problem after I installed a kit. Took it back apart and re cleaned it. Especially the needle valve and seat. Cured now. NORM
 
(quoted from post at 08:15:10 11/24/15) I had the same problem after I installed a kit. Took it back apart and re cleaned it. Especially the needle valve and seat. Cured now. NORM

Right. I was also thinking about how cruddy the carb was when I cleaned it. I soaked it in gasoline, sprayed it with carb cleaner, soaked it in gasoline again...shook it around and used some plastic putty knives and pics to loosen stuff up.

When I dumped the gasoline, there were a lot of little black pepper lookin' cruddies floating around and some bigger pieces of brown rusty lookin' things.

I was wondering if, maybe, there could be some residual crud that would loosen up after I put it back together and then screw the carb up.

When I put it back together, I was already thinking that it might be worth it to crack it open just for a re-cleaning and maybe blow it out with air again after a couple of weeks.
 
Soaked it in gas well that does not do much to clean it since when running it has gas in it. You need to soak it in a good carb cleaner soak if you can find one or in something like paint thinner. You also need to use a piece of wire or as I do a torch tip cleaner tool the poke out all the passage ways. As for the main jet can you screw it down and have the engine die?? A good starting point for the main jet is 2 turns out. If it has black smoke at that turn it in til the smoke stops and try it and see how it runs
 
(quoted from post at 09:28:37 11/24/15) Soaked it in gas well that does not do much to clean it since when running it has gas in it. You need to soak it in a good carb cleaner soak if you can find one or in something like paint thinner. You also need to use a piece of wire or as I do a torch tip cleaner tool the poke out all the passage ways. As for the main jet can you screw it down and have the engine die?? A good starting point for the main jet is 2 turns out. If it has black smoke at that turn it in til the smoke stops and try it and see how it runs

Could only find carb cleaner in spray form. I did use that, and I put the little nozzle into all of the holes and sprayed until I saw it come out the other side.

Paint thinner? I suppose I could get a gallon of that. That would be enough to soak the whole darn thing.

It does die out when the needle valve goes all of the way in. Kills it.

When I thread the needle valve out, I don't get skipping or smoking until it's almost all of the way out.

It's better than before, but maybe that bowl vent isn't perfect.

I wonder if welding wire (.035) would be a good "tool" to push through all of those little orifices and wiggle around???

Maybe take it off, rummage some welding wire through the orifices, soak it in paint thinner overnight...then blow out with another can of carb cleaner the next morning???
 
(quoted from post at 12:56:16 11/24/15)
(quoted from post at 09:28:37 11/24/15) Soaked it in gas well that does not do much to clean it since when running it has gas in it. You need to soak it in a good carb cleaner soak if you can find one or in something like paint thinner. You also need to use a piece of wire or as I do a torch tip cleaner tool the poke out all the passage ways. As for the main jet can you screw it down and have the engine die?? A good starting point for the main jet is 2 turns out. If it has black smoke at that turn it in til the smoke stops and try it and see how it runs

Could only find carb cleaner in spray form. I did use that, and I put the little nozzle into all of the holes and sprayed until I saw it come out the other side.

Paint thinner? I suppose I could get a gallon of that. That would be enough to soak the whole darn thing.

It does die out when the needle valve goes all of the way in. Kills it.

When I thread the needle valve out, I don't get skipping or smoking until it's almost all of the way out.

It's better than before, but maybe that bowl vent isn't perfect.

I wonder if welding wire (.035) would be a good "tool" to push through all of those little orifices and wiggle around???

Maybe take it off, rummage some welding wire through the orifices, soak it in paint thinner overnight...then blow out with another can of carb cleaner the next morning???
here are passages smaller than 0.035inch in those carbs. "paint thinner" is terribly generic. Mineral spirits is paint thinner & will do little in carb cleaning. Lacquer thinner will do better, but carb cleaner is the ticket. Do you know which passages are your bowl vents? Sounds like you want to target those specifically.
 

My F0-4 manual pointed out the bowl vent passage as one of a few passages that go from the top of the bowl up to the throat, near the throttle plate.

The manual showed it running near the "economizer" passage; which my carburetor doesn't have.

I concentrated the spray tube of the compressed can of carburetor cleaner into every passage that I could see in that area.

Torch tip cleaners? I don't have a set of them.

Do I need them?

If welding wire (.035) won't fit, one can get some really fine wire by cutting a piece of stranded wire...say...18AWG stranded, stripping it and pulling out individual strands. I also have a little bit of solid bus wire for electronics (24AWG, 30AWG) around....that HAS to be able to squeeze up in there...
 

I looked for carburetor cleaner at Tractor Supply...maybe if I checked out NAPA, or a real auto place, I could find quarts or gallons of parts cleaner or carburetor cleaner or something even better than paint thinner...
 

NAPA does have cold parts cleaner...but....yeeeesh! The MSDS for it sounds more toxic than Chernobyl, as in....face shield, respirator, chemical gloves, chemical apron....one of the components of breakdown is....Phosgene gas...I thought only Calvin from Calvin and Hobbes used Phosgene gas... yikes! No thank you.

http://s7d9.scene7.com/is/content/GenuinePartsCompany/683472pdf?$PDF$
 
LastLostCowboy, Make sure that you have the fiber washer under the needle valve seat and that you have it honkered down 3 grunts tight.Gag will leak around the brass needle valve seat and cause the carb to over fill and flood over as you describe,even though the needle shuts off the gas.(Hint)A set of guitar strings work good to clean out carb passages,all different sizes and just cut them to the length needed.
 
You don't need sealant. Liquid gas should not be that high in the
carb anyway other than splashing. If it is that's a different problem.

If you were still getting floating particles out of it, the carb isn't
clean. Canned carb cleaner and air are not enough to clean one.
Those passages meet and go several different directions inside.
Air and/or carb cleaner will take the path of least resistance
leaving the other portion of the passage basically untouched.
Good examples in JMOR's picture below.

Soak it in carb cleaner. Leave it two or three days if you want.
NAPA sells a gallon of carb cleaner specifically for this.
Comes in a gallon paint can with a dipping basket.
Not the best I've ever used, but it does a good job.
Link below.

If you think the flanges and gasket may be a problem, lay a
piece of 100 grit sandpaper on a sheet of glass or similarly smooth
piece of material, then set the gasket edge of your carb halves
on the sandpaper and gently stroke them across the sandpaper.
That levels them out pretty quickly, so watch the sanding marks.
It is cast, but not cast iron, so it sands quickly.

As Den said, guitar or banjo strings work pretty well.
I'll also second making sure the gasket is under the seat and
making sure that mating surface is good and that the seat is tight.

If you do the turn it on, not moving fuel test, do it with the air
breather hose disconnected so you can see if fuel leaks out
of the throat of the carb instead of the hose hiding it.
If you leave it overnight, put something under it to catch it so
you know for sure it didn't just hit the ground and evaporate.

30388.jpg


NAPA Carb Cleaner
 
Yeah,

I think that I made a couple of rookie mistakes putting the rebuild kit into the carburetor.

The mating surfaces definitely could use some sanding. They were pitted badly.

It sounds as though I may not have "grunted" the needle valve seat in.

I just happen to have a source for guitar strings.

Worst of all, I think that the diagrams in the F0-4 manual had me confused as to the actual location of the main jet. Is it all of the way down in the bore underneath the long nozzle...as in, you take out the nozzle and then stick a thin screwdriver down the bore and turn out the main jet...then replace it?

I have a couple of days off for Thanksgiving. Looks like I'm taking this carb apart again.

Thanks all.

I'll report back after turkeyday.

Hope that all of you have a relaxing holiday.
 
"I think that I made a couple of rookie mistakes putting the rebuild kit into the carburetor."

Don't feel like the lone ranger. That's how we learn! You didn't damage it.

"Worst of all, I think that the diagrams in the F0-4 manual had me confused as to the actual location of the main jet.
Is it all of the way down in the bore underneath the long nozzle...as in, you take out the nozzle and then stick a thin
screwdriver down the bore and turn out the main jet...then replace it?"

Yep, that's exactly how you get to it. [b:665d0eec5e]IF[/b:665d0eec5e] you want to.
And [b:665d0eec5e]IF[/b:665d0eec5e] it will turn out without damaging it.

I always replace them, needed or not, because that's what I'm paid to do.
Sometimes I have to use heat to get them out and sometimes
I have to drill and re-tap the threads depending on what's there.
They may have already been damaged by previous attempts.

You may not need to remove it at all and trying to do so may
cause you more trouble than you need to go through.
The most important part is making sure it is clean and the
passageways are open and clean.

If you do decide to take it out, a hollow ground gunsmithing
screwdriver works better than an every day screwdriver.

"Hope that all of you have a relaxing holiday."

Same to you and yours!
 
cowboy.......NEVER honk down on yer carbie screws, the carbie is SOFT and you will WARP the metal around the screws and it will LEAK. 2nd, yer float valve seat needs a fiber washer under it or it won't seal. 3rd, twirl yer float needle inside yer valve seat so you gitta good seal. Needle should have a ring around it. 4th, check that yer float floats. Many of the BRASS floats have invisible pinhole leaks. TIP: shake yer float, iff'n yer ears are good, you'll hear gas sloshin' BAD float. Me? I haffta float it in glass of water, iff'n it sinks guess what??? BAD float. As the guys recommend, sandpaper onna glass mirror, and sand yer carbie. Will fix yer WARPED screw holes. .....the warped Dell
 
(quoted from post at 12:53:52 11/25/15) cowboy.......NEVER honk down on yer carbie screws, the carbie is SOFT and you will WARP the metal around the screws and it will LEAK. 2nd, yer float valve seat needs a fiber washer under it or it won't seal. 3rd, twirl yer float needle inside yer valve seat so you gitta good seal. Needle should have a ring around it. 4th, check that yer float floats. Many of the BRASS floats have invisible pinhole leaks. TIP: shake yer float, iff'n yer ears are good, you'll hear gas sloshin' BAD float. Me? I haffta float it in glass of water, iff'n it sinks guess what??? BAD float. As the guys recommend, sandpaper onna glass mirror, and sand yer carbie. Will fix yer WARPED screw holes. .....the warped Dell

So,

I stopped at NAPA after I got the turkey today. Found the carburetor cleaning kit suggested by Royse. Going to soak the carb over Thanksgiving and clean it out, re-install Friday. That is, after I sand the surfaces on a glass plate.

I noticed that the float was way, way more than 1/4" off of the gasket (when held upside down) with the new needle valve installed. Note that I do remember putting the fiber washer under it. I'm now thinking that I shouldn't have gone right to bending the float, as recommended in the FO-4 manual. Maybe I should have done Dell's twirl-the-float-valve procedure first to make sure that the float valve was really fully seated when I measured the float distance to gasket.

When I put it back together, I'm going to check that to make sure that the float needle has a little ring on it and is fully seated, to Dell's specifications, :) when I measure the distance.

I'll also check for leaks as suggested.

I'm now wondering if I can get double duty out of that 96 ounces of carb cleaner. Maybe soak/clean the carb; then strain it through a cheesecloth and use some of it to clean up my hydraulic pump; which I plan on dropping to clean up when I change the fluids for the winter.

Wouldn't that do a good job cleaning that pump up?

Thanks
 
Carb is back in the tractor.

I disassembled and removed all of the parts that I had previously put in from the kit.

This time I did actually find where the economizer jet and the main jet were. I removed both without much trouble at all. I just so happen to have some gunsmith screwdrivers in my electronics toolbox.

Luckily, I had held onto those jets from my kit. So, I had new ones on hand.

It had a good soaking in a NAPA carburetor cleaner kit, and I put a B string from a six string acoustic guitar through all of the orifices.

I think that my leak came from not tightening the needle valve seat enough. When I disassembled for cleaning, I noticed that I didn't have the washer under the seat compressed. I stopped tightening too soon, apparently.


Reassembled with all of the new jets this time.

It took a lot of force to get that needle valve seat to compress the washer, but I made sure that it was compressed at least a little this time.

Back on the tractor. No leaks so far.

It's adjusted to run OK for now.

Remember that the tractor has a tank full of ATF-laced gas in it right now to help clean out the valves.

I figure that I won't be able to get a perfect carb adjust until I've run that through and have it running on straight gas. That ATF-laden stuff burns a little weird :)

Hope that all had a good Thanksgiving!
 

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