good choice. my buddy had an f2.. i think they are great learning bikes.

the knocking.. it could be a lot of things. most likely (in my opiniion) it could be the valves needing adjustment. how many miles are on the bike and when was the last time they were adjusted? in reality though, no one will be able to diagnose a "knock" or "tap" over the internet, it would have to be heard in person.