Simple way to tune a nitro engine, asuming the fuel line and the tank is in good shape-start the engine and let it warm up with the glow igniter still attached, after a couple minutes remove the igniter and run the engine to full andpinch the fuel line before the needle if the engine speeds up lean it a little untill she does not speed up and then back it off a little then pinch again and she should speed up just a little you have the high speed set. Now the Low end-bring the engine about 2 to 3 clicks above idle and pinch the the fuel line again if she speeds up lean the low end untill she no longer speeds up and back it off the width of your screw driver blade and pinch again if she just slightly increases before dying you good to go.