So, don't know why I thought this but it's just dawned on me, a 'parallel' twin (to which I referred to as an ordinary twin) is different from an 'in line' twin. I thought all the twins from years ago which I owned were just all the same less the obvious 'v' twin configurations but they are not. That answers the fact that my Chinese touring bike (ER6 based) being an 'inline' twin doesn't have anywhere near the big bollocks of my Bonneville 'parallel' twin torque. So, that brings me onto another matter, Yamaha's R1 these days sound like 'V' fours from changing the firing orders from the traditional 'inline fours' to the new configuration but.......... Has there ever been a 'parallel' four unlike an 'inline' four where all four pistons rise together and fire at the same time i.e. same similarities to the Bonneville? First one to answer that will get a sticky bun at the GMU2017!! Yum yum
Not sure, but wasn't the Ariel Square 4 essentially 2 parallel twin engines bolted together??? Edit, just checked... opposing action.
To build an inline 4 with all pistons rising and falling together is to manufacture imbalance into a system and require a large counter balance fly wheel or similar... the opposing rise and fall naturally counters that imbalance.
Thinking of the cross plane four that is in the R1 I wondered years ago why four cylinder four stroke engines had their cranks designed so that two pistons were at TDC and two at BDC not understanding about the forces involved that need balancing so the engine can run without vibrating itself to bits. I was brought up on two strokes, singles then twins and eventually triples which had even firing spaced at 120degrees of crank rotation like our speed and street triples. If only I'd learned about that kind of stuff I could have invented the cross plane four and been a brazillionaire by now.