Biggest tricks? --> Don't overlook the mechanics of the engine:
- main bearings aligned?
- main bearings have correct interference?
- con-rod has correct clearance on both ends, and checked for parallel ends and in twist direction as well?
- crank running *dead* true?
- cases dead square?
- bottom of cases perfectly flat? Top of motor mount perfectly flat? (Yamaha cases bend/flex easily)
- correct end play in the crank?
- bottom of cylinder dead square to the bore?
- is the piston you're using square? (wrist pin bore to the sides)
- check taper of piston (more radical tuning requires more taper, milder exhaust and lower gears less taper)
- is the cylinder deformed correctly for honing so it will be perfectly round when engine assembled?
- DON'T over-tighten the exhaust header (deforms bore) - very low torque and double-nut is best (same torque as when honing)
- does the ring *perfectly* fit the bore size? (light checking is best).
- shoot for the correct ring tension, end gap not critical as long as it has enough
- choose an assembly sequence and torque increments on every step, and try to always do it the same way
- give the top of the exhaust a slight bit of an "arc", don't make it straight across (way easier on the ring)
- when it comes to cutting cylinder or head, I'd personally cut the head if I can get to the squish I want
- combustion chamber shape can definitely change the power band:
----- small diameter deeper dome for for short/tight tracks
----- larger diameter shallower dome for tracks where a lot of time is spent at higher revs
PM