Making an instructable for this was an afterthought, so I apologize for not having step-by-step photos.
This summer I decided to try and reduce our water usage in our toilets.
We have three 1.6Gpf / 6.0Lpf toilets throughout the house.
My first thought was to use the old 1/2 gallon milk jug in the tank trick. Upon opening the tank, the space was so small, I knew this wasn't going to work.
I shortly considered using a couple of bricks, which might have fit okay, but I really wanted to reduce the water usage more than that volume.
I wanted to reduce water consumption to approx 1 gallon per flush.
After studying the mechanism a bit, I thought I might be able to modify the float valve system to suit my needs.
This proved to be very easy to accomplish.
What you're trying to do is to adjust the angle of the float ball so it closes the tank fill-up valve sooner as the ball floats on the water.
This involves bending the rod and anchoring it with a lock nut.
Step 2: Unscrew the float ball from the metal rod
Be careful with this step, as you don't want to damage the plastic valve assembly.
Most likely the treads will be corroded a bit and it might be a little stubborn, so use a pair of pliers to grab the rod while you unscrew the ball.