As a professional engine builder (but less and less these days, marc), I've done most everything you can do to a set of gears, and shafts.

• A great (read as 5 to 10 hours of labor) gearbox job generally includes:
   

  • Shimming to minimize lateral play on the gears. (to builder's judgment)

  • Shimming to move each fixed gear closer to it's sliding mate (but not too close) (to builder's judgment)

  • Shimming shafts to move the assembly closer to an optimum position. (to builder's judgment)

  • Using a surface grinder to make your own custom thickness shims.

  • Making sure that you place the "rounded" side of the circlips against any shim or gear

    • That puts the "sharp" edge of the circlip nicely in the circlip retaining groove on the transmission shaft so it doesn't "ramp out" under side loading..

  • Checking and adjusting shift mechanism "fingers" on the shift star "pins". (to builder's judgment)

  • Checking, replacing gears with worn engagement dogs and slots - or undercutting worn engagement dogs.

    • I tend to try to use as little angle on the undercut as possible, as the more undercut the angle is, the more you have to let off the power to get the gears to separate - important when not using a "quickshifter" or "air shifter".

  • Deburring of most gears, most shafts, the shift drum and the shift forks

    • A commercial facility, such as Supertech, owned by the iconic Dennis Zickrick in Colorado, does metal finishing and low friction coatings.

  • I don't recommend cryogenically treating powdered metal gears, like most Japanese type gears are - I don't feel it's a good use of the process. I'm not saying that "cryo" is bad, as I do use it at times for pistons, springs, knives, unfinished gun barrels... just not powdered metal gears or large finished machined castings.
     

• Additionally, separate from the gears and shafts, there's the shift mechanism (shift shaft, selector device, shift fingers, detent arm and spring, detent star)
   

  • Checking straightness of shift shaft (sometimes they get bent on the left, shift linkage / rearset side)

  • Polishing sliding parts in the shift mechanism (to decrease friction of shift drum rotation - and "quicker is better")

  • Reducing friction of the detent arm (arm needs a bearing - which we make as a model requires and "quicker is better")

  • optimizing detent arm spring pressure (if the spring pressure should be changed, we make - and "quicker is better")

  • optimizing detent ramps (if the ramps aren't right, we make replacement "stars" - making it "quicker")
     

• Adding an EVO Shift STAR kit -
   

  • In general, if the gearbox is setup "alright" (I would say that most stock, original, undamaged transmission are "alright"), that just adding the EVO Shift STAR kit is going to be 80% to 90% of what is theoretically possible in improving shifting quickness, reducing missed shifts, decreasing rider effort and protecting the shift forks and gear engagement dogs from damage caused by missed shifts.
     

• How do you know that a transmission is shifting quicker and more reliably?

  • You can feel it when riding.

    • Even when hand shifting on the bench, it's easier to get out of gear and "snicks" into gear, rather than "clunks" into gear (yes, most Kaws won't shift into 2nd unless the output shaft is spinning :-)

  • You notice that you only have time to slightly "twitch" the throttle off a teeny bit between shifts and hardly have time to pull the clutch lever even a little before the bike's already in the next gear.

  • You "try" to miss a shift on bench or riding and almost can't.

  • Your "quickshifter equipped" bike shifts clunkily after an EVO Shift STAR kit install and you have to decrease "shift kill time" by 5 to 15ms to accommodate the EVO STAR's quicker shifting.

    • That 5 to 15ms is now converted to "engine power" time, rather than "engine kill" time.
      That will improve power delivery time on a racetrack and at the drags.
       

    • Funny story - an AMA team called up and said the bike's shifted awfully clunkily after the Shift STAR - I was mystified and in talking, we couldn't figure out why the riders claimed the clunkiness - as in the pits, it was def. quicker - and didn't even think to ask about whether they were using a quickshifter.
      They called up later and said that they figured out that the "quickshifter" was now killing the power too long and it was perfect when they decreased the shift kill time.
       

      • BTW - for roadracing, a perfect QS system will have several factors to program. Should still be pretty easy to sort out - and there's nothing commercially available as or Feb 2009, on the market that's "right" for roadracing, though most all are are fine for drag racing and  "alright" for roadracing and that includes the guy who supposedly built his own Suzuki ecu, (well, he did make the box at least - the ECU seemed to be a repackaged EFI Technologies ECU according to the software)