yes and no
hows that for an answer?
in a perfect world:
pistons,connecting rods, ect would weigh exactly the same ( not rotating mass )
the crank/ flywheel can be " balanced" as a unit (rotating mass)
the ratio of reciprocating mass is controled by the counterweights/piston weight,connecting rod weight ( the whipping around parts)
these weights ( reciprocating )are " chosen" to produce frequencys ( engine vibration ) more or less at ( less at useful rpms) , ( more at un useful rpms ( more " shake " at idle ) )
good crank harmonics ( i think) is when the velocity of the reciprocating mass matches the energy of the " countering " energy ( perfect harmony) ( no shaky, shaky)
this will only occur at a specific rpm
so if you balance a crank/piston assmbly to operate with no vibration at low rpms it might shake badly at the high rpm range
and if you balance for high, it might shake at low ( more shake a idel)
in a two cyl
the engine can create " sympathetic " frequencys
where a crank can create vibrations at low and high
i.e 1000 rpms no vibe,4000 bad shake, 7000 rpms no shake,12000 smooth
this would be due to " phase cancelation"
at this point i have to tell you that im not an engineer and all of the above could be wrong.( so somebody correct me if im wrong)
hope i helped
what was the question?
i need a job