overflowing carb problem

Been trying to figure out why this Zenith 9667 carb I'm dealing with, runs over and I'm totally stumped. It's been doing this for a long time and now I'm going to find the problem come he!! or high water.

I've had this thing apart and it's clean. The tractor (SC Case) purrs like a kitten. But if it sits for a period of time, the float bowl seeps over. I put in a new needle and seat and with the carb on the bench I hooked it up to a gas tank. With the bowl off I can turn the carb upside down and the weight of the floats is enough to shut the gas off. I can leave it sit there that way for awhile and it stays dry. Put the bowl on, turn it over so it's sitting the way it would be on the engine, turn the gas on and slowly it will start seeping over the top of the bowl after three minutes of waiting. The floats are level with each other, the hinge pin is new and not binding. The float hinge doesn't seem to be worn noticeably and the floats can't be wiggled side-to-side more than maybe 1/64th of an inch, maybe a bit more but it's close, the floats are straight and seem to be in the middle of their individual chambers in the bowl and not touching anything. The floats aren't leaking and adjusted per instructions. They do sit level with the carb upside down.

It just seems like the floats don't have quite enough push, when floating in the bowl, to completely close the needle. I have a couple more 9667 Zenith carbs so I took the floats out of one of them just to compare and they look to be the same. When the float bowl starts to run over the foats are totally immersed by a shy 1/8" so I assume they are maxed out and can't push up any more than they are, so setting them lower won't do any good.

That's about the best I can describe it. I've been messing with tractor carbs off-and-on for a good 40 years now but I'm no expert by any means so now I'm leaning on you experts for some advice or tricks. What else can I check? The gas tank I have it hooked to is a lawn mower tank so it doesn't have a lot of push. Thanks, Jim

What else is there besides a faulty needle and seat or gas in the float?

Had one with rubber tipped needle. Had to change it to all metal needle. Dave

This is rubber tipped. One of the old carbs still has a metal tipped one and it looks pretty good yet. I could give it a try. Just seems like the gas in the bowl doesn't push the float up quite as hard as it should. Question- and it's way outlandinsh- has the specific gravity of todays gas changed? Jim

I have fixed a mystery flood over with a rubber tipped needle by grabbing the needle by the shank and dragging the rubber tip across a rough cloth like blue jeans, coveralls etc. This removes bits of rust and metal that imbed in the rubber and prevent a gas tight seal to the seat.

Also I have had good success with pushing the rubber tip needle quite hard into the seat so it shapes that area of the needle to the seat.

I have found many seats to be less than perfect. I use a pintle from an injection nozzle and reshape the hole in seat with a few light taps on that pintle with a small hammer. Some times you can even see the that the hole is not round.

#1 you should always shut the gas off at the valve when you park it so gas will not get in the oil which it will do if you keep having that problem. #2 with the rubber tipped needles you have to set them to the seat which you do by opening up the carb and drop that needle into the seat and tap on it with a small screw driver handle or some such thing. Look at the tip of it and if it has been set you will see a ring on the rubber area of it. #3 you may not have the needle seat as tight as you need it and it is leaking past the seal

Check the floats they may have some fuel in them making them to heavy to stop the fuel. Also the fuel pressure may be to high. Don't try to fix the floats replace them the solder will increase their weight.
Walt

Not leaking past the seal but I never thought to look for a ring. Thanks. Jim

Floats are dry inside and the tank I'm using for the testing is a lawn mower tank that holds a gallon at the most so I highly doubt the pressure is too high. Oh, as a side note, this is the one and only tractor I have that has an inline car filter in the fuel line and it has worked great for the past 15 years. I was having trouble with junk plugging the carb even after I had made darn sure the screen in the sediment bulb was good, and after the ol girl stranded me a mile away from home I cut the line and put in the car filter. Haven't had any problems with junk or fuel delivery. Jim

Trick I learned from an old man who is dead now and he told me about the setting of the needle in the seat with the new rubber tipped needles. He was a carb man for a local tractor dealer by the way

Well I tell ya, I tapped on the needle, rotated it a bit, tapped again, put it together, hooked up the hose, and it's been sitting there on the bench for maybe fifteen minutes and it's still dry. I don't have the screws in to hold it together so it should have leaked over the top of the bowl, but it didn't. Thanks again. I get lazy and I don't turn the gas off on this tractor, or any of them, for that fact. Jim

Seen more the one tractor that had over full oil pan that was about half gas and that is not a good thing. I learned a long time ago to shut the gas off and have even gone back out to double check that I did so gas cost to much to have it on the ground and or in the oil pan

This might have something to do with it huh? After I seated the needle it worked once and then overflowed. Tapping on it stopped the overflow. Took the float off and it was then that I noticed the misaligned hinge pin. Put the float back on, took a look and I could see right away it was crooked. Why didn't I see this before? (sigh)

Did some tweaking to get the float a little more centered and so far the results are positive. Can't get it to overflow no matter how many times I drain the bowl and let it re-fill. It's gonna sit in a big pan on the bench with the fuel on all night before it goes back on the tractor. Jim

"the floats are straight and seem to be in the middle of their individual chambers in the bowl and not to..........."

hummmmmmmmmmmmmmm

I tried to get the camera straight up but it's kind of tough. I eyeballed it for a long time and found out the top of the carb isn't built centered but the floats were off to the left. Tweeked the hinge point, had it binding, had to cure that, about left the shop for awhile, but persisted and now it's working OK. Can't knock success. Jim

send it to popin john [email protected] 845-626-5870

YUP ! That would sure cause the problem. One just doesn't expect something like that.
Walt

A quick lesson in fluid mechanics:

The amount of fuel is irrelevant to pressure on the needle. The HEIGHT of the fuel is the only factor that matters.

You can put 1 gallon with its surface 12" above the needle, or 100 gallons with its surface 12" above the needle. The pressure at the needle will be the same.

Put 1 gallon of fuel with its surface 24" above the needle, and it will have twice the pressure as 100 gallons with its surface 12" above the needle.