You will be in a better position to negotiate the value if you have documentation to support what you feel the bike is worth. Whatyardwork's suggestion of finding comparable bikes in the area is good advise. Another good suggestion is go over the description of the bike with the adjuster before they obtain their value. Make sure they have all the options/accessories, have the mileage correct, and the general condition of the bike is accurate.
Keep in mind that the initial amount they quote is just that; an initial offer. You don't have to accept it, and you can always make a counter-offer. The insurance adjuster most likely got the value by inputing data into a vendor's evaluation program, and the value given is an average of what similar vehicles are selling for. Some companies will use NADA or Blue Book valuations. Others will use programs with propietary software to provide the value. In some cases you will find state law actually dictates to the insurance companies how they must establish vehicles. One example would be requiring the valuation to be set at the average of 3 major evaluation services such as NADA and Blue Book.
In most states, vehicle registrations will include the amount you stated you originally paid for the vehicle for sales tax purposes. If you reported an artificially low number then, don't expect to be offered a higher value later unless you can support upgrades that raised the value. Yes, they will likely look at the state's registration data to make sure you're the owner. Also, if you have a "stated value" on your policy, that's the most that they will pay regardless of what the bike is actually worth. If it's worth less than that however, they will only pay the actual value of the vehicle.
Also, if your state/province charges sales tax on vehicles, make sure they include the appropriate amount of sales tax on top of the valuation. You'll have to pay it on the replacement bike, so it is an expense that should be covered under the policy. Also, they should be wiling to pay a pro-rated amount of your registration remaining for the year. Again, this depends on the specific requirements of your state/province.
As for going up the ladder to get a better price, don't depend on that tactic. I'm actually one of those people "up the ladder", and unless you can support what you feel the value is with good, legitimate, examples, the offer likely will not change. With that said, it can't hurt if the adjuster doesn't seem to be willing to work with you. Just keep the conversation professional, and support what you say with facts. In most cases, the adjuster is more willing to work with you if you don't go "over their head", and don't act beligerant.