If I am to purchase an expensive mountain bike, will it be covered under my homeowners insurance policy, or must I purchase separate insurance?

Like most of your personal property, your new mountain bike should be covered under the named perils section of your homeowner's policy. If your bike was stolen from your home while you were on vacation, it will most likely be covered under your homeowners policy.

One thing to keep in mind is that if something happens to your bike, and you need to replace it, your policy deductible will probably increase the actual value of your bike. The best way to deal with this kind of issue is to probably call your homeowner's insurance agent and talk to him about this problem. Ask if they offer replacement cost coverage, which then would reimburse you for the actual cost of your bike, if something were to happen to it.

If your homeowners insurance does not provide coverage for your mountain bike, consider buying a floater. A floater will cover more perils, provides replacement cost coverage with no deductible. An insurance company will probably require you to have your bike appraised when purchasing a floater.