David22........I don't know what kind of smoke system you have, but the one I had in a U-can-do 60 was a TME system using a 6oz tank and the engine was a ST2300. Great smoke, but it lasted maybe 8-10 seconds. I had to build a brass coil inside the muffler and I may have not put enough restriction at the end. Needless to say........an ST2300 on a 60-sized plane is overkill and the thing would start gaining speed even at the lowest of idles. Just dumping a stream (or heavy mist, even) into the muffler isn't enough.....the muffler has to be hot enough too.......so prewarming the oil before you spray it into the exhaust gas's hottest point (just as it exits the cylinder), becomes essential.
Oh, don't forget to check out TME's site for recipes on different smoke oils. http://www.tmenet.com/brews.htm