Some insurance companies (Farmers I believe) will allow you to put recreation vehicles under your homeowners, but make sure that the associated bump in premium for doing this is really worth it, and find out what it covers exactly.
FWIW, I have fire and theft only with Progressive on my '02 KDX, and the premium is only $137. Keep in mind though that $137 includes a special Michigan-only surcharge of $72 to help fund an "unlimited" claims fund due to Michigan's no-fault law. So really, the premium on the bike is only $65 per year. It also covers up to $1,000 in custom parts/accessories.
www.bike-line.com also has very good rates.
Also, if you are an AMA member, Progressive does offer a discount, but it only applies in some states. Check the AMA web site to see what states qualify.
IMO, for dirt bikes, the only coverage you really need is fire and theft.