Neither Kelly Blue Book or NADA are very accurate for motorcycle values.
What I do is go to Cycletrader.com and punch in the year, make, model of the bike i"m interested in (search the whole country) and look at what they are going for. If it's an older bike, search for 3-5 model years around the year you are looking at.
Jess, that could also be very misleading. I bought my Valk for $1,500 less than advertised , and most recently last month bought an 08 1800 N it was listed at $8.900 and we closed the deal at $ 7,000-