Thanks for all the advice, but nobody answered my question. I still don't know if I should offer 90% of msrp or if that would be an insult.
It depends on the dealership. Lakehill and Southern Powersports will not take a dime less than they quote you. They are the highest volume dealers in the country and their price is cut in stone.
Dealing locally I'd start at 80% of their asking price.