Depends on the engine..Generally 2-strokes dont produce enough heat like the 4-strokes do so you need to pre-heat the oil some way by either using a smoke muffler or wrapping some brass tubing around the header or the engine head itself before injecting into the muffler. On my Saito 1.20 I tapped the header and wrapped the muffler with insulation and aluminium tape. It makes good smoke. Minnflyer gave me his setup...Main thing is you need to get the oil as hot as possible..

Im using a TME pump and I have a Don Harris on my gasser..Slimline makes a good one also.