I don't remember any of my Saito engines being hard to adjust or run rough. Sometimes it is individual perception of how a engine runs too. One person might think the vibration is bad and another things it is OK. So it is hard to tell actually. But I rebuilt my Enya 1.20 four stroke engine a few years ago, and on its first engine run and it just about destroyed my test stand because of the excessive vibration. It actually inured my thumb and forefinger holding the throttle lever. But after I dialed it in better, it did smooth out a lot more. Of course my test stand was somewhat messed up afterwards. One problem with four stroke engines is that I find it difficult to just about impossible to tell what the engine is doing from just its sound only. I have to use a tachometer to adjust it.