Carburetor Needle Seat Valves

Dave in GA · Sep 28, 2009

I've got some unrestored 1930s row crop tractors that run well. If I don't fire them up every weekend, some of them don't like to start because the carb needle valves stick up in the little plastic seats and won't let any fuel into the bowl. It's the same problem I've had with Tecumseh lawn mower engines and their similar needle/seat valves. I've tried adding some Marvel Mystery Oil to the gasoline and that helps some, but it gets old having to take a carb apart to get the tractor to start every other time. The carbs are clean inside and out, as they have been disassembled, cleaned with choke and carb cleaner, and reassembled. Are there any tricks to keeping these needle valves from sticking in the seats?

twopop · Sep 28, 2009

when you shut the engines off,why not turn off the gas and run the engine out of gas so the valve will be open,therefore will not stick

Anonymous-0 · Sep 28, 2009

Maybe change your gas supply, if all engines do the same.

Dave in GA · Sep 28, 2009

I forgot to mention that when I shut the tractors off, I cut off the gas and let the engines run until the gas is out of the carbs. This should leave the floats and needle/seat valves in the down/open position. The sticking must be happening when the gas is turned on again and it fills the bowls, raises the floats, and pushes the valves up into the seats.

GeoMo · Sep 28, 2009

PLASTIC SEATS?
ANY CARB. I HAVE BEEN IN HAS BRASS.
I DO NOT KNOW WHAT COME IN THE KITS NOWDAYS BUT 30 YEARS AGO YOU COULD BUY NEEDLE AND SEAT KITS AND SEATS WERE BRASS.

NCWayne · Sep 28, 2009

You don"t say whether the needles are the solid type or the ones with the rubber tips. It seems to me like the sticking occurs more with the rubber tipped ones than the solid ones. I guess because the rubber will deform and stick in the hole to give a tighter seal they have a greater tendency to hold on even when the bowl is dry. That said if they have rubber tips why not look around and see if there are any solid ones available and give that a shot.

Too, while I"m a fan of Marvel Mystery Oil for many uses, I know Sea Foam seems to do alot better job for me on engines that set than anything else I"ve ever run across.

Barring anything else have you tried something simple like, after draining the gas, just give each carb a light tap to, hopefully, cause the float to drop and unseat the needle?

Lamar Fudd · Sep 28, 2009

Dave, I believe what's happening is that your fuel shutoff valve isn't totally shutting off the fuel. It seeps into the empty carb and raises the float which then cuts off the gas but now the needle is stuck. On carbs that I've rebuilt there is a hair spring that "pulls" the needle down as the carb empties. It attaches to the float arm and the end of the needle in a groove.

old · Sep 28, 2009

2 things you should do that if you do it will stop your problem plus a few other problems to boot. #1 shut the gas off and let it run till it dies from running out of gas. #2 pull the carb drain plug and drain what ever gas is left inside so it will not go bad and cause things to get sticky. Doing those 2 thing will cause the float to be down so the needle will be open and can not stick in the seat

Carburetor Needle Seat Valves

Dave in GA

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twopop

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Anonymous-0

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Dave in GA

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GeoMo

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NCWayne

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Lamar Fudd

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old

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