First take it for a test drive and pay close attention to all the parts. if something is wrong you can repair it and/or buy it just to make sure your covered and you should make a maintenance check every year if you care about your bike.
the one you maintain the most
That depends on how you ride and maintain it.
Keep it clean, lubed and rattle free. bicycletutor.com will probably have a link for it.
A triple tree is the part that is found on the front fork of the motorcycle. These units allow the bike to maintain structural integrity so they can be properly steered.
change the oil. higher grade of gasoline. change air filter
No. Maintain the pressure stated on the side wall of the tire.
It is all about aerodynamics. In short yes lowering the bike affects the handling of the sport bike. If you are going to lower the motorcycles rear end 1" then the front end should also be lowered 1" to maintain the ride dynamics. You can find more info on this topic @ www.ronincycleparts.com
An exercise bike can aid anyone in loosing weight. However, it's important to maintain a varied and healthy lifestyle - you shouldn't restrict yourself to only using an exercise bike. Try other means of exercise too (perhaps take part in a sport) and eat healthily.
Repo whats left of the bike, sue him for the balance due, get a judgment for that amount, attempt to garnishee his wages. Contact his ins. co. IF you required him to maintain insurance coverage.
== Primary, not sole?== Implicit in the question is that you were not the sole owner. If you were, then your ex had no right to maintain possession of the bike, since you would have had the sole right to sell it. If you were the sole owner, you may have to sue him or her for it.
about up to 12 miles per hour but you should see the world record
Make sure you change your oil every so often. Make sure you keep your chain tight. Clean your air filter everytime you ride it or buy a new one. Make sure everything stays lubed. Dont rag the bike out and you should be fine.