I sold a Harley here in the UK a few years ago and had a similar problem trying to value it. Two things worked:
1 searching e-bay and looking at what was being asked and what was selling, far from the same thing!
2 Talking to a local bike dealer who offered a commission sale deal. He took 20% but he offered finance and warranty to buyers and he had a good on-line shop so he could charge at least 20% more than I could as a private seller.
In the end I opted for the commission sale with the dealer. He gave me a choice, fast sale or wait and see what you can get. I went for "wait and see" so he priced high, monitored hits then made a small reduction every 3 months. In the end it took near on a year to sell but I ended up clearing slightly more than the price I was going to list it at on e-bay (and no e-bay fees) with a great deal less hassle. No buyers, silly questions or returns, just a payment.
So if you are in no rush consider a commission sale with a dealer who specializes in British bikes. At the beginning I balked at the 20%, at the end I thought he'd really earned the money and it was good value.