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dads706

Why always updraft..?

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Just curious, why did all the tractor manufacturers stay with updraft carburators? I would have thought that downdrafts would have been a way to boost HP a bit. But I can also see that it may have caused some design/engineering issues.

Please understand that I am somewhat mechanically challenged.

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Having chosen that feature for a user name, I should be an expert on the subject, but I am not. One reason which comes to mind is the use of an updraft carb keeps it mounted low enough to allow gravity feed from the gas tank. I think F-14 and F 12 used a fuel pump, but most didn't. Lowers production cost with one less needed part.

Charlie

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Updraft also made for a good way to keep a stuck float from literally filling the whole engine with fuel if left long enough.

Briggs and Stratton used to have their carburetors on their vertical shaft engines set up so that they has a slight up hill climb to get into the intake port but then decided to change it so that the intake port was below the carburetor so that now whenever the float sticks it dumps the whole fuel tank into the engine creating all sorts of problems.

A little change can make a big difference in how something works or does not work when a simple part doesn't do what it supposed to.

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learned that in an in-direct way when dad and i put a 350 v-8 in my massey harris 44.. electronic fuel pump is necessary to get fuel from tank to carburetor, as the carb bowl sits higher than the bottom of the tank...

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I'm not positive on this but was told, that the down drafts back then iced up easier also .

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Updraft also made for a good way to keep a stuck float from literally filling the whole engine with fuel if left long enough.

JD Two Cylinders use a gravity fed side draft and will indeed fill the crankcase with gas if the needle leaks and you haven't shut the fuel valve off. The later series have an automatic fuel shut-off run by oil pressure. I've had one of those fail as well.

In either case you get to do an unplanned oil change. The up-side is the oil stays clean for a long time afterwards!

The lesson I took is only use rubber tipped needle valves. I had the same problem with an International but, as stated, it didn't fill the crankcase, just leaked all over the shop floor. Lesson learned there was to shut the fuel off if parked inside. Also replaced that needle with rubber tipped. I found my local Deere dealer stocks the seal and diaphragm kit for the auto shut-off for a nearly 60 year old machine!

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