Yamaha TRX850 Enthusiasts Forum

http://sense.net//~blaine/270.html

Some light reading on what advantages the 270* twin has over a 180* twin.

Good reading - I'd read about the XS650 conversions.
I presume he states "Therefore, maximum piston/rod mass velocity is achieved at 74.1 degrees B&ATDC" because of the non-sinusoidal motion of a reciprocating piston/crank when the piston travels more during the first 90 deg. of travel than the second 90 deg. to bottom dead centre. That in itself is a producer of secondary vibration.

I've always found it amusing when Yamaha astonished the world with it's revolutionary "crossplane" engine in 2009. The same company had being doing it since 1996 when the TRX was launched and Cadilliac with their V8 in 1923! - As my old man would say, "There's nothing new"