Edgar---you don't need a tach---Use the pinch method--Pinch the fuel line and close the needle until the pinched line won't allow the engine to lean anymore then back it off a click or two--Use a mixture control to adjust from there. The pinch method takes some practice to get perfected---If you hold the pinch too long you will lean out the engine and not get a good needle setting...A quick pinch it what it takes---BV tought me this almost 20 years ago!!!

Kevin