Once that piston starts moving down after TDC(about 20-25 degrees) - Your breather might as well start opening. At 5/16" after TDC it should be opening for sure. It should stay open all the way to BDC. Get that air out of the crank and create some suction on the way back up to get the oil out of the top end. Oil is friction. The ability to reduce friction and drag in an engine is important when trying to make adequate power, eliminate oil consumption - and calm down internal pressures. I don't have a lot of performance mods on any of my bikes. Everything is kinda stock - or mild performance. But, I try to get the most I can out of what I got - so my shit starts and runs halfway decent. It's fun knowing this stuff, reading manuals, trying to understand how everything works will help you diagnose potential failures, etc . . . and always listen to your elders.