When doing a big bore kit, you need gears. Without them you are never going to take advantage of the extra power. Choose whichever set fits your needs. I suggest going for taller gears, if you do a lot of flat top speed riding, and shorter ones if you like acceleration, and stop/go.,Rebuild your final drive while you’re in there, get the full rebuild kit HERE,Replacement gaskets HERE!,16×42-16×36 is best for 72cc builds, 9.2:1,17×41 is best for smaller cc stroker bikes, 8.2:1,18×41 is best for large cc stroker bikes, 7.9:1