@awnlee jawking
I want my protagonist to own a variety of motorbikes, preferably all from a single manufacturer. His first will be a low-powered bike to put-put around the town where he's attending college. Later ones will be a timeless classic powerful enough to hold their own in penis-measuring contests.
Suggestions?
I can offer many suggestions, as you can see. But I will need more information from you to give a realistic list of bikes to consider.
First, the years this story takes place in. Realistically, the bikes should be no more than about 10 years old to be considered to be "realistic, good condition, and affordable". Unlike cars, bikes do tend to have a much shorter lifespan.
Secondly, the general economic class at each stage of the story. A lower class character might start with a moped like a Puch. Middle class, something like a Honda Rebel, Suzuki GN400, or other entry level bike. Upper classes might just jump straight to a Harley Sportster.
This is like saying "Help me pick a car", but without knowing the era and economics, that is really impossible. As I may be thinking the 1970's or early 1980s and say a Datsun, and you are talking 1930s where it should be a Model T.
And while many people are throwing out a variety of makes and models, the issue is that without knowing the income level of the main character, it might be way out of their price range. For a middle-class college student, a $20,000 bike is really out of the question. As is picking something so rare that only a real wheel-head would even recognize it.
Also, unless you are only wanting to use Honda, you might want to pass on the "single manufacturer". For a "timeless classic", that would likely be some form of cruiser, and then your options are very limited. Largely only to Honda, Harley-Davidson, and BMW for the most mainstream manufacturers. All companies have made cruisers, but many for only a short period of time, and as such they rarely became "classics".
Like the Yamaha Venture Royale, which has come and gone and changed drastically over the decades. Where as from 1975 until 2010 when the design and production was moved to Japan the Goldwing actually changed very little.