thinking of buying a sport bike

rode my kz400 for a couple of months now (tx for the help i got from
ppls here!), but with a worsening oil leak under the breather cover
and winter closing in, i'm looking forward to the sport bike i want to
be riding next sping.

i love my kz, and want to continue to fix it up. but after making it
run i want a bike that i don't feel neglectful for riding, and that
doesn't make me worry it will break down if i stray too far from home.
and being able to do 60-65 in 5th w/ the wind blowing at me wouldn't
be bad

after not bidding on a beautiful cbr600f4 that went for 3050 on ebay
[kick], i printed out a used bike buyers guide:

http://www.clarity.net/~adam/buying-bike.html

and decided to go look at some bikes in my area. first one was a 94
cbr600 f2 (i like hondas) w/ <10k miles that i was hard pressed to
find flaws with. the owner is moving out of state and barely rides
it. he pointed out a small scuff from what looks like a single drop.
sprocket, chain, forks, wheels, tires, frame, fairing, brakes, clutch,
shifting, electrical-thingies all looked/operated/seemed in good to
nice condition (but i'm still new at all this). bike started right
up, but i didn't ride b/c it was raining.

so here's what i'm wondering:

after fiddling with the choke (which seems to offer more than just
on/off), the bike ran for 60 seconds and started making noises i
couldn't place. not a pop, and not a sputter, but somewhere
inbetween. no fire from the pipe. it seemed to lessen/stop after
about 3-4 min. the bike didn't seem warmed up yet, because there was
still some throttle bogging (choke partially on, 65F). the owner
turned it off w/o waiting for it to fully warm up and said it would
probably run right w/ fresh gas.

he also mentioned some type of air adjustment located around the
petcock, but said it shouldn't be adjusted when the bike was running.
is that an air intake valve for the carbs?

so...

does this all sound normal for this type of bike/seller? i don't have
a lot of confidence in my ability to judge the situation. any advice
appriciated, technical or otherwise

-- john

ps: he wants approx 3k.
pps: vote