Hey Guys, one day I was perusing Facebook Marketplace and came across an ad for a Champion 20" Lawnmower with a 3.5hp Briggs & Stratton flathead engine. Then I messaged about the mower and got it home.
Once I got it home, I fired it up and noticed the engine was running rough. Then I looked for a carb kit and bought a replacement carb/fuel tank kit since it cost the same.
After installing the new carb/fuel tank kit, I fired up the lawnmower, and it ran really well the first time, but when I tried to start it the following week, it wouldn't run.
This led me to believe it was a fuel issue, since newer gasoline has more ethanol and a lower boiling point than older gasoline.
At about the same time, I was watching several YouTube videos on installing a propane conversion kit on a portable generator. Then it clicked: I could install a propane conversion kit designed for a portable generator on my lawnmower, since both a portable generator and a lawnmower run at 3600rpm for extended periods of time. So, I did.
Then, I bought all the required items, such as the propane conversion, 1/2 psi barbecue regulator/ hose come, some blue 1/4" fuel line, 2 1lbs refillable propane cylinders, 1lbs cylinder adaptor fitting, and a brass 1/4" barb to 1/16" male NPT fitting to connect the fuel line to the carburetor.
Then, I drilled a hole into the side of the carb to install the brass fitting to feed propane gas into the venturi portion of the carburetor before the throttle plate.
Next, I plumbed and leak-tested the entire propane setup and mounted one of the two propane cylinders on the left side of the handle.
After I was done, I tested the mower, and it ran like butter, cutting the entire yard without a single stutter.
As of now, I'm happy to report my lawnmower has cut the lawn for 2 seasons straight and continues to run smoothly since I built it in 2023.
The only things I have had to do since then are refill the 1lbs cylinders and change the oil every season.