Tecumseh Carburetor Replacement
Article by Mark Trotta
The original carburetor was missing off this old Tecumseh motor, and I needed to find a suitable replacement. Trouble was, the original part numbers have long been superseded and/or discontinued.
Fortunately, most Tecumseh carbs have only minor differences, so with a little homework you can find one that will work correctly.
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There were several types of carburetors fitted to Tecumseh flathead engines. Some will have chokes, and some will have an idle adjustment screw. Smaller horsepower engines (Tecumseh H25, H30, H35) may have neither of these.
Finding A Replacement Carb
The first replacement carb I bought had a primer bulb, but no choke, and was non-adjustable. It fit correctly but the motor wouldn't start. The primer bulb was working, as gas was getting into the float bowl, but it just wouldn't start the motor.
After looking online for a solution, I found a forum member with the same problem. He remedied his situation by switching to a carburetor with a choke.
Choke Carburetor
The second carb I purchased was a replacement for carburetor numbers 631921, 632284, and 631070A, which are commonly found on Tecumseh H25, H30, and H35 engines.
Shop: Tecumseh Replacement Carburetor
Applications for this carb include many Tecumseh-equipped snow blowers, which operate in cold climates and need a choke to help it start. It is also a popular replacement carburetor for Troy-bilt roto-tillers.
NOTE: If the choke lever on the new carb is too long and is causing fitment issues, you can trim it down with a cut-off wheel or a hacksaw (carefully).
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Along with the new carburetor, a new Champion RJ19LM spark plug was installed.
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Air Cleaner
All gas engines need some type of air filter to keep dirt out of the carburetor, and small engines are no different. With the exception of initial break-in and troubleshooting, you should always run your engine with an air filter.
I was missing the original air filter, so I bought a high-flow air filter from Amazon.
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Should I Remove The Governor?
Most vintage Tecumseh engines have a mechanically-activated governor. It's controlled by a rod that passes through the aluminum case, and an arm connected to the carburetor with a long spring.
The governor on a small engine is designed to do two things. First, it helps maintain a constant engine load, but it also limits maximum engine speed, which protects the engine from possible damage.
Should you remove the governor on your kart motor? If you're not racing your kart, I would recommend leaving it in place.
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Governor Adjustment
Check that the rod is not binding and the governor spring is not overly stretched. A deformed spring will affect governor operation and should be replaced.
To adjust governor for best operation, perform the following:
- Loosen the clamp screw
- Move lever so carb throttle plate is wide open
- Rotate the governor clamp clockwise as far as possible
- Rotate the governor rod CCW as far as possible
- Tighten the clamp screw
- Check for binding
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