Yep, I did that. I also have used an unlit (turned on) propane torch
held above a carburetor on older car engines that would not run, and
appeared to be due to a lack of fuel. If the engine ran with the
propane, then I knew for sure that the problem was not ignition, and was
definitely fuel related. This also assisted an engine that kept killing
because of partial or poor gas delivery (usually a partly plugged carb
or fuel filter).
I could keep the engine running, while adjusting the carb, and not have
to keep restarting the engine. If it could not be adjusted, then I had
to check other things, like the filter, fuel pump, etc.
There was a trick to doing that, which was to shield the torch tip, so
the propane was getting sucked into the carb, while still allowing air
to enter the engine. Just a slight move of the torch would make a huge
difference in how it ran, (or quit running).
I still remember, probably 30 years ago, when my car quit running and
was blocking traffic. I had a buddy sitting on the fender, with the
hood open, and he was holding the torch over the carb while I slowly
drove the car over to the shoulder. But since it got the car to the
shoulder, we decided to see if we could drive it to his house, which was
about 1/2 mile away. Of course I could not see the road with the hood
up, so he had to tell me what to do. That was pretty insane, but it
worked, even though I must have had to restart the engine at least 25
times!
(We later found it was nothing but a clogged fuel filter).
I dont know if this would work on modern fuel injected engines????
It might work on a lawn mower, I have never tried it!!! (HINT HINT for
the OP).