Your engine is not dialed in right. Fuels,props and plugs wont' do much until you do.

You sound like you know the basics of tuning and engine.

So lets see where you are. Run it up for a minute or so to get it warmed up.

1. While the engine is at an idle, disconnect the fuel line fro the nipple on the carb. if the engine rpm increases before the engine quits your low end is to rich-close the needle a tad. It the engine rpm just goes down and quits, your to lean-open it up a bit. Now this maybe 1/16-1/8 turn.

You may want to intentionally put it to lean and to rich to see reactions you get. I like to go for a slight increase.

On the high end needle. Give it a pinch test. Most go for a quick increase n rpm. I go for no change. This stuff is in fine print in all engine manuals but most are not aware of it. It works very well