i would guess you are talikng about a timing advance key. all it is is a woodruff key that is offset a few degrees to advance you timing. it rotates the flywheel to advance the timing, usually about 4-6 degrees. It is supposed to give a crisper throttle and some power gain.
Tyler Jones
2000 426EX, 11:1 wiseco, hot cams stage 3 "stroker" cam, Ported head done by Dr. G, FCR 41, Hot rods crank, running no base gasket, 1 layer of 3 layer head gasket, Klotz 113 race fuel Feather carbon smoothie hood, works tripples w/ressies, Black HMF slip on, AC pro peg nerfs, Azonic fat bars, burgaurd +1 1/4" swinger, Lonestar +1 stem, douglas yellow label front wheels, Pro Armor front bumper, + some others goodies
AIM: Fourtrax426
Holeshot Motorsports Wilder, KY
for all aftermarket parts