I have a 20 horse briggsanstratton rider... when I try to start it all it does is click at the solenoid... I just got a new one an its still doing the same thing... what would I check next

If the soleniod is "clicking" that is a good sign it is working. The starter unit is what you need to look at. Also Im assuming the battery is fully charged. If not start there first.

A new one what? Starter?

Clicking is generally a sign that the battery's internal resistance has increased so it cannot provide the current to turn the starter.

Either have the battery checked or jump it using a car battery. Car not running.