Cheap HP

[Booster]

Discussing this on another forum and i thought to bring it here
won't be new to some...
Reduced windage from cyl to cyl.many newer bikes have cutaways between cyls to reduce pumping loss, apparently in some engines it can be worth 3-4 hp.
Something i have been doing for several yrs.
Before
http://img.photobucket.com/albums/v378/maj750/DSC01985.jpg
After
http://img.photobucket.com/albums/v378/maj750/DSC01984.jpg

[EFE 1230]

Does removing that much metal affect strength of cylinder liner?

[Issues]

it should not be a problem, Have you not seen inside a 2 stroke engine that had scavange ports?

The Kawasaki H2 Mach iv had bigger ports in the barrels half way down.

[Booster]

No strength issues, compare the piston skirt to the cyl material the piston is 1/4 the thickness of the cyl, and the only load on the cyl is from the skirt as the piston changes direction
another pic shows the cyl better
http://img.photobucket.com/albums/v378/maj750/cylinders.jpg

[Hagarr]

Besides, it's not on the thrust (skirt)sides so won't affect much.

[Stocky]

Crankcase vacuum also helps.

You can achieve this a few different ways depending on the bike.

There is some suggestion that connecting all different areas of the engine together via a common hose helps too.

Suzuki run 3-4 diffent crank case vents on their MotoGP engine all to a common collector and then use the exhaust to draw a vacuum.

Yamaha have valves built into the cylinder head to pull air from the top cover and the gearbox.