One of the reasons I still have my '75 RD350. Dead simple and darn near bulletproof.

The variable valve timing (one or both valves) can have a significant effect on emissions, as well as tractability. Seems like Honda went through quite a number of iterations, originally using electro-hydraulic actuation of more radical cam lobes/followers. I think most of the current methods use variable timing (usually hydraulic) on drive pulleys/sprockets to achieve more continuous variation. As to the question of locking in the timing at the radical setting, there's a pretty good chance the engine would barely idle, and would certainly pollute like crazy. Oh, and the mileage would really suck, something quite a few people are concerned about. I remember the bad old days of carbs and fixed valve timing on car engines. Put in a radical cam to generate big torque/HP numbers at high revs, and the thing would barely idle, be a bear to start, and make very little torque off idle. In those days getting one HP per cubic inch was the sign of a temperamental, tightly wound engine. Nowadays that's a standard engine, with tightly tuned engines (like 600 sport bikes) getting around 3 HP per cubic inch. Probably couldn't do that without all the electronic tweaks. I still like riding my old R80RT (only engine electronics are ignition) But the power output is uninspiring.