Regarding using an un-lit propane torch to check the fuel mixture.
First, when you are doing this you must disable any governor.
On a X Y graph, Draw fuel lean or rich on the bottom X line(so very lean is 0 and very rich is far to the right (a high value on X axis)), and draw RPMs on the vertical Y line so very low RPMs are near 0 and very high RPMs are high on the Y axis. Visualize, or draw a curve shaped like a mountain with the Y peak about half way down the X axis.
You will require some means to measure the RPMs of the engine. Some simply use there ear (hearing protection is a real good idea, you are going to be running the engine for a while, and you will be near it).
You can use the propane method to set idle and high end on the carburetor. Set the throttle to the end of the scale you will be working with (idle for idle, high RPMs for main adjust), and leave it at that setting while you are using the propane to test lean or rich, and if adjusting the carburetor, and then re-testing with propane, until you get it to where you are satisfied with the setting.
There are some sites on the internet that give information on how to do this. One recommends that in order to be consistent, you first light the torch, and adjust the flame to about one inch. Then you leave gas valve set for that level of flame and extinguish the flame (usually by placing the tip against the ground for a brief time).
To find out if your engine is running lean or rich, you simply place the un-lit torch tip with the gas coming out at the rate that would make a one inch flame (if it were lit, but it is not lit) near the air intake for the air filter, so that the gas is sucked in the air cleaner along with the air going in while the engine (fully warmed up) is running.
When you do that you have substituted some gas (fuel) for some of the air the engine would normally be getting, and as a result you have increased the fuel mixture temporarily. What is nice about doing it this way is that you have not had to adjust anything on the carburetor to do this. The RPMs will change, either increase, or decrease. If they increase, then the engine was running lean and your engine is running on the left side of the peak of the mountain curve.
If the RPMs decrease when you add the propane, then the engine was running rich and it is on the right side of the mountain curve.
The RPMs of the engine will follow the curve of the mountain. If you start out on the lean side (if you engine is set lean), and increase the fuel in the mix(by adding propane in place of air), the RPMs will increase with an increase in fuel. If you are on the lean side, the increase in RPMs will continue as you add more propane, until you reach a peak. After the peak, if you increase the fuel, the RPMs will fall off.
Ideally you want the engine to be just a very slight amount on the lean side of the peak. It would be nice if the RPMs would increase about 20 or so RPMs as you begin to add some propane, and if you add more propane (get the un-lit torch tip closer to the air intake), the RPMs would stop increasing (be at the peak in the mountain curve), and with even more propane the RPMs would drop (because the engine is now rich in fuel).
There are other examples of how to use a propane torch to check or set the fuel mixture of a carburetor on some sites on the internet. You could google it and read them if you require more information on how to do this.
