Place the bike onto a bike lift and raise it until the back tire has completely cleared the ground.
Push up on the rear shock preload adjuster until you can turn it. Choose a different setting. Generally, higher preload will result in lower seat height, and lower in a higher seat height.
Repeat the process for the opposite side shock.
Lower the bike off of the lift and sit on it to test it.
If it is still too tall, try again. Once you've reached the highest preload setting, and if you still can't place both feet flat on the ground, you will have to modify the suspension.
Replacing the rear shocks
Place the bike on a lift and raise it off the ground so that both wheels no longer touch the ground.
Place a block underneath the rear wheel.
Remove both the top and bottom bolt from each shock and gently pull on both ends of the shock simultaneously. Do not yank it, as this may cause the bike to fall off the stand.
Install the new, shorter shocks. To align them, lift the rear wheel until both the top and bottom mounting holes are aligned at once.
Bolt the new shocks to the frame with the mounting bolts that should have come with the kit. Do not use the old bolts.
Tips & Warnings
Since you will be lifting the bike off the ground, it is a good idea to have a second person around to help keep it steady while you work on it.
Do not over-tighten the bolts. Over-tightening can cause the bolts to weaken and shear under stress, which may cause an accident.
You should also have the front fork modified to maintain the riding geometry, but you should not attempt this work yourself. This is precision work -- and beyond the skills of most home mechanics.
