641 carb woes

On my 641, I just got the restoration done, or so I thought. Got everything back together, as it had been sitting for about 5 months. In February I had it running like a watch. Background info:

134 gasser, completely rebuilt
Rebuilt distributor with all new parts
All new Echlin parts in the ignition
12V stealth conversion with generator
Brand new harness, plug wires, every wire on the machine
TSX580 carb, rebuilt

If you aren't familiar with it, this is the machine:
http://forums.yesterdaystractors.com/viewtopic.php?t=1229444

So I crank it up to pull out for pics, and it will only run with the choke. Absolutely seems carb-related and not enough fuel. Starts very easy, runs smooth with choke. Release choke and it shuts right down. Got tons of fuel coming out the line into the sediment bowl. Clean sediment bowl. Good fuel flow into the fuel bowl.

Take the carb off, fully expecting to find the main jet clogged. Thinking this is not rocket science, I've done it a million times before. Find that the fuel had started to varnish after only 5 months.....very smelly. Nice. Clean out good, blow out all passages, put back together, no change. Did this three times now. For the record I found no ports clogged at any time, just that varnish smell of the fuel. Scratching my head at this point. There is no difference hot or cold, it just won't run without the choke on.

Any thoughts as to what I am missing? Must be something stupid in this carb. It had been running like a watch previously. I can't see where spark could be an issue.

Thanks!
Kevin
 
Doesn't matter what "good flow" you have "into" the fuel bowl, but what do you have "out" of the carb bowl drain? Next, dump the old "varnish smelly" gas & use fresh.
 
(quoted from post at 22:50:34 07/27/15) Doesn't matter what "good flow" you have "into" the fuel bowl, but what do you have "out" of the carb bowl drain? Next, dump the old "varnish smelly" gas & use fresh.

There is tons of flow out of the bowl drain.....equal to what is coming in, and that varnish stuff is long gone.

I think I'm likely missing something obvious.
 
vacuum leak maybe , could be between manifold and head or between carb and manifold, drain tank and put in new gas. I have seen some of the carb kits come with the wrong main jet needle too
Boss
 
If you've got good fuel flow through the carb to the drain then
my guess is you've got a piece of dust/sanding grit/etc stuck
in one of the passages somewhere.

I would clean them out with compressed air and run a banjo
string or similar through them to make sure they were open.

You don't have any smart alec neighbors who would have turned
the main needle most of the way in just to mess with you do you?
 
Main jet of the carb has a problem. Does not take much to mess one up. Dirt or rust in the jet area or venture tube will cause that. You can have all the gas in the world into the carb but if you have just one little piece of dirt etc in a passage way yep it will not run like it should.
 
Got it.

Old nailed it. There was some slight debris around the main jet, although it would allow compressed air to go through it. Did as Royse mentioned and ran a thin wire through everything, that's when I found it. Was hard crust junk.

Back to normal now. Thanks again for the help.

Now, after all of the whining about being burned out on a restoration, there's an old Mustang calling my name, ready for some tweaking. I guess the break after the tractor restoration is gonna be short...

Kevin
 
(quoted from post at 00:40:28 07/28/15)
You don't have any smart alec neighbors who would have turned
the main needle most of the way in just to mess with you do you?

...and no, seeing that the tractor was in the garage and locked up, they'd better not be in there!
 
(quoted from post at 19:45:57 07/28/15)
(quoted from post at 00:40:28 07/28/15)
You don't have any smart alec neighbors who would have turned
the main needle most of the way in just to mess with you do you?

...and no, seeing that the tractor was in the garage and locked up, they'd better not be in there!
The kind of smart alecs I was talking about would be your friends.
You let them in to see it and when you're not looking they try to
pull a "harmless" joke on you. It wouldn't hurt a thing other than
the amount of hair you have left trying to find it.

Where did you find the crud? That stuff can build up under the
jet which is why I always take them out. Especially if they have
set for a while.

Taking them out can cause its own set of issues though,
including stripped out threads. No fun when that happens!
 
LOL, nobody I know even wants to touch it. And everyone says "I can't believe you're going to run this thing." So I hope we're safe from shennanigans for a while at least.

It was under the main jet. I blew through it the other times and also shot carb cleaner in there. Was still open, but restricted, and obviously enough to matter. Also, I can't quite prove this because I had only a subtle "feel" of something temporarily, but I think there's a vertical passage in the center that may have had similar issues. Regardless, the wire, more carb cleaner, and compressed air did the trick.

I gotta get some non-ethanol stuff in there.

Thanks again,
Kevin
 

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