[moeller80]

I have noticed many air cooled engines not require valve adjustments in their specifications.

Can anyone shine light why water cooled engines require these intervals outside of the BMW's?

The new Indian and other air cooled engines do not have these have such requirements.

 

[azccj]

It has to do with hydraulic lifters which adjust for the correct valve clearance. Has nothing to do with if the engine is water cooled or not. These type of engines typically have lower top RPMs, like those that are used in HD cruisers.