A Yamaha XS 650 with offset crank pins. Yamaha's legendary XS 650 family consists of motorcycles that the British should have built.
However, it is not the case that these parallel win are "inverted BSAs." The basis of the block is rather with Horex and the 2 liter six-cylinder block that Yamaha technicians built for Datsun.
But the 360 degree crankshaft configuration is of course just like the British. And according to many Yamaha XS 650 enthusiasts, that is precisely the weak point in the concept. XSs walk and sound like British twins of yore, but they don't leak oil and stay whole.
Oh yes: at higher speeds they vibrate just like the British twins did. That is why things tear and some things shake loose. You can live with that.
Those XS enthusiasts who had difficulty with that and thought that the engine would run better and perform better if the lever taps could be set to 270 degrees.
The resulting ignition characteristic would make the engine vibrate less, run smoother, rev it, and deliver more mid-range torque.
In terms of splines in the crankshaft, the crankshaft is moved by 277 degrees instead of the technically correct 270 degrees that can also be achieved. But the block doesn't seem to care much for that few degrees difference. The expensive solution to put the matter purely on 270 degrees is of course also an option.
Oh yes: the camshaft must of course also be adjusted. And the ignition.
The most funny side effect is that the changed ignition timing also changes the sound of the Yamaha XS 650. Such a good Japanese person suddenly starts to sound like a Ducati.
All in all, this approach makes an XS650 a better machine.
And just about everyone who drives around with 277 degrees has had the conversion done at the world famous Jerry vd Heiden in Yamaha XS 650 circles.
