Farmall Cub Runs Great On Chainsaw Carburetor

Farmall Cub Runs Great On Chainsaw Carburetor TRACTORS Modifications Paul Peyton didn’t want to spend the money for a new carburetor for his Farmall Cub tractor so he used one off a Stihl chainsaw The carburetor is bolted to a paper air filter element designed for a 12 hp Tecumseh engine and to the tractor’s air intake manifold “As far as I know I’ve got the first Farmall Cub in the world with a chainsaw carburetor ” says Peyton “I came up with the idea because the carburetors on Cub tractors are famous for being unreliable leaking fuel and starting hard I had to rebuild the carburetor on my Cub 3 times over a 2-year period but it still didn’t run well ” says Peyton of Huntsville Mo “I know people who have junked their Farmalls because they couldn’t make the carburetor work and couldn’t find a good replacement “I priced a newer replacement carburetor but the $249 price tag encouraged me to seek alternatives I’m a retired engineer and mechanic and have a lathe and a Bridgeport vertical milling machine so I figured I could come up with something better I decided to use a chainsaw carburetor because it develops a lot of power for a small engine and because it’s designed in such a way that it can operate in any position The Stihl carburetor’s bore is larger than the Cub’s so I knew it would have adequate airflow ” Peyton says his homemade carburetor has worked even better than he hoped “The tractor now starts instantly is more reliable has more power and doesn’t leak fuel Also it’s more fuel efficient because the Stihl carburetor does a better job of atomizing gas ” The tractor’s original air filter was under the hood and the air intake above the hood They were no longer needed so Peyton removed both of them The chainsaw carburetor originally was equipped with a built-in fuel pump connected to a small fuel line with fuel pumped by pulses in pressure from the chainsaw’s crankcase But on the tractor the carburetor had to work with a gravity flow system which required modifications “The fuel pump side of the carburetor had to be altered sealed and tapped so I could run a standard 1/4-in fuel line and fuel filter to the tractor’s gas tank ” says Peyton He machined a new governor linkage bellcrank and pivot as well as an adaptor plate and air filter mounting plate which were machined from aluminum bar stock The carburetor’s adjustment screws were shortened and re-slotted to allow for the bellcrank and governor link Linkage from the bellcrank to the carburetor was fabricated and the governor linkage was modified where it screws onto the carburetor “I wanted to use a modern paper filter and found one that was designed for a Tecumseh engine But in order to make room for the air filter I had to shorten the tractor’s oil filter tube ” says Peyton “I also had to discard the tractor’s large breather-type oil filler cap I fabricated an O-ring sealed oil filler plug with a folding handle and a dipstick that threads into the center of the plug ” The tractor didn’t have a “breather” cap on the oil pan so Peyton fabricated a positive crankcase type of vent system A rubber hose allows blowby from the engine crankcase to vent into the carburetor’s intake airstream “The Cub’s original carburetor wasn’t adjustable but the Stihl carburetor has 3 screw-type adjustments one for high speed one for low speed and one for idle speed ” Contact: FARM SHOW Followup Paul Peyton 4373 Hwy D Huntsville Mo 65259 ph 660 998-4204; peyton paul@gmail com

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