Originally Posted by DogBoneR1

You might want to break the countershaft sprocket nut while you still have the wheel and chain on the bike. That way you can step on the rear brake to keep the engine from turning if it's really on there tight. Once that's off then cut the chain and remove the rear wheel. Once the wheel is off install the new sprockets. Snake the new chain around the countershaft and measure what you have to cut off. Press it back together and you'll be on your way. Dont forget to bring your wheel forward before you cut the new chain.

It's easiest to press the new link on if you have it on the back sprocket, holding the two ends together.