Posted by Fixerupper on June 26, 2012 at 10:28:49 from (100.42.82.164):
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
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