Try:
americansandassociation.org
or glamis dunes.com
if you're flexable on the price, it'll sell.
New 4 stroke Honda 250's (very popular) are $3300 OTD at LA Honda and people calling you will tell you that in efforts to deal on price.
At least they did with me.
I sold my last set of quads on atv trader.com in about 20 minutes.
the trick is flexability on price.