Probably not absolutely necessary but I use them on all my saws that have one, even my 353 Husqvarna. A few years ago I didn't ever use a de-comp but since I've had shoulder problems I notice it helps me a lot. I have a 290 that I made into a 390 and it is rather hard on me to start it but I manage by drop starting it. I will tell you that my de-comp equipped saws are fast becoming my favorites...I don't think a decomp is ever necessary on a little saw like a 361. I'd be looking for something else