GP shift
 

I don't understand how they are using stock motorcycles to race. I heard you have to have GP shifting to race. Stock bikes don't come with that. Do they have a rearset alteration to enable them to race?

Anything can be raced...

Not all racers use GP shift. Many do, but it's in no way mandatory.

As for how it's done, there are several ways. On many modern sport bikes it only involves taking the stubby lever off of the shaft that comes out of the transmission and turning it over. On older bikes it can be more of a pain, but it's always possible. On the FZR600s I used to race I eliminate the linkage and use a one-piece lever from a 70's-era Japanese bike (nearly all Japanese shifter shafts are 11mm diameter with 36 splines). With the lever on pointing backward the shift pattern is reversed. I had to bend the lever around with a torch to get the pedal where I wanted it. On a Triumph 675 Daytona I had the stubby transmission lever was easy enough to flip over, but because the linkage went through the frame that wouldn't work. I took a piece of stainless rod and bent it around until it could work as linkage outside the frame, then threaded both ends to 6mmx1.00. One annoyance was that on most linkage one end is left hand thread, meaning the purchase of a left-hand die.


With regard to aftermarket rearsets, it depends on what you buy. Some include extra hardware needed for the shift pattern conversion, but many won't. One of my bikes has Italian rearsets on it which consisted of pegs and levers which weren't even left-and-right-handed, and a few bolts. The expectation was that I'd fabricate the rest.