Ford 641 Carb?

mcg1238

Member
Hey,

Long time reader first time poster. Quick back story I have been wanting an old ford tractor for a long time. Two weekends ago I purchased a 641. It smoked a little black smoke and was back firing. But ran well other than that. I hoped it was just running rich, spark plugs indicated it was also.

Next day I changed all the fluids, cleaned all the oil parts/breathers/air filters ect. When I drained the oil it smelled like gas and was thinning. I took off the air intake line and it was full of gas.I figured the float was stuck or something was wrong with the carb so I purchased a rebuild kit.

Today I attempted to rebuild the carb ***MY CARB IS A MARVEL SCHEBLER TSX692***. Last night I let the carb sit in berrymans chem dip (overnight). I took detailed pictures and videos during disassembly (BUT WHO KNOWS IF IT WAS ASSEMBLED RIGHT PRIOR TO MY DISASSEMBLY). Today i put it back together as it was during disassembly. Hooked it back up to the tractor and it wont start and fuel is pouring of of intake side of carb/in intake hose from air filter when i disconnect it.

I have tried to do a search of my specific carb to see if I am missing something but I cant find a specific diagram just the general TSX ones. The only thing I cant find that wasn't in the rebuild kit or on the carb when I disassembled it was the "Jet-Power" which is "under the "Nozzle Main". Any idea what would be causing this carb to flood so much that fuel is getting in crank case/air intake hoes? Pics of current how carb looks after rebuild
Thanks!
 
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I have a hard time with pictures but in the 3rd one it looks like your needle valve is upside down. The point should have a black tip and it goes in the hole. As the bowl fills with gasoline the float pushes the needle up stopping the fuel flow. As engine runs the fuel level in the bowl goes down. Needle valve opens allowing more fuel in. It repeats as neccesary.
 
Does it flood/leak just setting there?
If so, your needle valve and seat are not seating correctly or
the seat is missing the gasket under it, or not tight enough,
a crack in the casting around it, etc. Most likely not seating.

If the flooding occurs after trying to start it, different story.

The main jet is not your problem, some models don't have one.
I can't remember for sure if the 692 did.
 
I will attempt to see tomorrow if it floods
without starting. If it does not what could
be the cause? What would cause it to flood
when trying to start?
 
The needle I took out was black needle with
a flat brass top on the other end. The new
one in the rebuild kit is red needle with a
lip for spring which hangs on float on the
other end. I did not put spring on as it
didn't have one during disassembly. However
that would only help when opening which
isnt my issue. I did test that it seats by
holding upside down and blowing into the
gas "in" line. I couldnt blow in. Leading
me to believe it is sealing...

***I should also add float only moves very
slightly up and down... like 1/8"****
 
"What would cause it to flood when trying to start?"

Too much choke. All the gas that gets sucked up the manifold
toward the cylinders will gravity feed back down once you stop
turning the engine over, flooding the carb and coming out the
air intake.

If this is what's happening, then I would check spark quality
on all four cylinders. An adjustable gap tester set at 1/4 inch.
They're about $8 at the local auto parts store.

Also, might as well clean the plugs with a propane torch or
lacquer thinner at that point. Or simply replace them.
Keep the old ones and put one in at a time after it is running
to clean/clear them while running the tractor.

These old Fords start a lot differently than other brands.
All they need is a tug of the spring loaded choke after the
engine is turning. Anything more than that may flood them.
That's why the choke is spring loaded to the off position.
 
Someone on here said to get the Ford NewHolland float valve because they are all metal. I bought two different aftermarket kits and they required different float settings because the needle and seat were somehow different. I also had a float needle that would stick up (for no apparent reason) when holding the carb in normal position. One other problem I had was the tractor wouldnt crank until I let off the starter button. I long as I held the button down it wouldnt fire up.
 
(quoted from post at 02:03:44 12/04/17) Someone on here said to get the Ford NewHolland float valve because they are all metal. I bought two different aftermarket kits and they required different float settings because the needle and seat were somehow different. I also had a float needle that would stick up (for no apparent reason) when holding the carb in normal position. One other problem I had was the tractor wouldnt crank until I let off the starter button. I long as I held the button down it wouldnt fire up.
I forgot to add, I believe the 641 tractor uses a TSX 765 carb. Someone here said they had a different carb number on their 641 and it would run good with choke partly on. Someone may have installed what they could get at the time as they are similar. Electronic ignition is very good. Check on here about installing. Are your throttle shafts sloppy or tight? They can suck air in through the sides and that may affect jetting suction flow.
 
Might try doing this to see where your gas levels out
at. This is on a N but should work for yours too. Also
the pic of your float looks like it might be a little
bent,make sure it?s not rubbing side of bowl.
a249303.jpg
 

Reread what Royse said. There is no hidden path from the carb to the crankcase. Your 641 had a non firing cylinder before you got it, that is why the black smoke, and gas in the oil. Get a compression tester and see which and how many cylinders are low compression and post back.
 

Reread what Royse said. There is no hidden path from the carb to the crankcase. Your 641 had a non firing cylinder before you got it, that is why the black smoke, and gas in the oil. Get a compression tester and see which and how many cylinders are low on compression and post back.
 
I didn't see it mentioned in the discussion, but check and make sure that the float doesn't have a hole in it and filling up with gas. Gas in the float will make it sink and open the valve even when the float chamber is full of gas. Take it off and shake it back and forth. Should feel and hear gas in it if it's leaking.
 
mcg, it is a little hard to tell from the pictures, but I think it looks like choke is installed wrong.
 
(quoted from post at 12:51:29 12/04/17) mcg, it is a little hard to tell from the pictures, but I think it looks like choke is installed wrong.


Pretty sure that is correct. It looks wrong. Shouldn't the choke be held open with a spring around the shaft?
 
(quoted from post at 20:41:27 12/04/17)
(quoted from post at 12:51:29 12/04/17) mcg, it is a little hard to tell from the pictures, but I think it looks like choke is installed wrong.


Pretty sure that is correct. It looks wrong. Shouldn't the choke be held open with a spring around the shaft?
es, and when pulled against the spring it closes it. It M/S manual has a drawing in it that is actually installed wrong & has no doubt trapped a lot of people.
 

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