When I take my quad down a steep hill and either put the brakes on or use the engine to slow me down heavilty there is this clicking noise. Is this normal? Anyone else have it? Thanks

 

Never heard such a noise out of my '00 450-S. Does it come from front or rear of the bike, can you tell? Loose rear driveshaft coupler bolts? Loose wheels?
How many miles are on yours? Hours?

 

sounds like it is right under my a$$. I have 240 miles and 30 or so hours don't remember. I know the wheels are not loose. it has always done this.

 

Loose/bad rear shock? The battery is secure, right? Check the connections at the battery while you are at it. Mine came loose twice in 2200 miles.
You may want to get it in to the dealer, just to cover a$$, in the event of a failure when it goes out of warranty. Good luck.
PS-- My frt. shock lower bushings went bad, and it would click at times. Yours shouldn't be, with 230 miles on it.