Im building a Pica Waco bipe 1/5 scale.The box says the weight will be between 11-13 lbs maybe a little more.I want to use a four stroke engine and the specs. call for a 90 two stroke or 120 four stroke, I want more power then this and am considering the 140 DZ 0r the 140 sport.This engine will be cowled in and will need to use a muffler,A stock 4/s muffler will prob. work?My question which of these two engines will be the best,Power will prob. be at about 1/4 throt. most of the time and i will need a smooth transition from 1/4 -full throt. Idle should be excellent. I have never owned a YS engine,But i want one now, might use the engine for a Pattern plane later. Thanks for any help Randy Wallace

If you want to go on to use the engine for pattern (2m), get the DZ. You may also want to consider the 110 which puts out slightly more than my Saito 150 did on the same fuel/prop combination, but only weighs as much as a 91.