Not exactly - a good 80 single can be very smooth - they are all counterbalanced , tho there is a midrange node due to them being a single - The YS 4 strokes shake mainly due to the "every other " power stroke has to do with lower number of prop power pulses per revolution.
My broken in well tuned ZDZ80's are extremely smooth - I expect the DA 85 will be very much the same .
Th spark ignition can be tailored to reduce much low speed vibration. seen quite an improvement in this in modern ignitions.
The other "vibration" is simply torque reaction- single - twin - all have it . I put spark ignition on a 1.4 ST and the low speed vibes smoothed waaay down
why no one offers a good spark setup for "glow engines , for competition use, is a mystery to me - For some users tho- they would likely just f it up
The so called injection engines are a case in point.