Now let's see what options you have:
1 Monkey ghetto conversion
2 Proper right way
I have tried them all.They all have pros and cons.
Lets see the ghetto one first.
There is only one pros - cheapness. The rest are only cons.
Let's see how small engine works. Most small engines run on constant RPM. Engine load constantly changes. Governor(usually centrifugal type) is trying to keep the same RPM by adjusting throttle angle (open and close). When throttle is opened engine gets more air flow in carburetor. This increased air flow will "pull" more gasoline from emulsifier tube. In this case air/ gasoline mixture is mostly balanced most of the time. When throttle is closing the process works the other way.
Now with our ghetto conversion we have some kind of pressure regulator (to reduce pressure of liquid propane to very low pressure) and some kind of adjusting valve. We have no gas flow control. We deliver the same amount of gas all the time. But engine's governor constantly changes throttle angle. We have imbalanced fuel air ratio and engine starts surging and backfiring and running like s...
Also it is usually hard to start engine that is converted to run on propane this way. You have to keep adjusting the valve to make engine run better but it will run OK and suddenly start running like s...
Here is an example of components I used for ghetto lawnmower conversion:
You can see adjustable propane regulator on right side (all small BBQs have them) and valve from propane BBQ. I brazed a small barb tube to the end of valve to connect hose that was going to carburetor.
Easy, free in most cases but don't expect your engine run smooth and efficient.
Here are some examples of this type of conversions
Here even child cold convert his lawn mower to propane
But again you can tell all this engines don't run properly and if you have not perfectly straight lawn you will end up adjusting the valve all the time.
Propane consumption in this types of conversion was 2-3!!!!! times higher compare to a proper conversion.
My 6hp Brigs lawnmower consumes less than 1lb (about 13 oz) of propane in full hour. It runs just perfect (much better than on gasoline). Starts every time from first pull.