[adouglas]

Insufficient info.

IMHO you can learn a lot by interacting with the owner. Is the guy knowledgeable and straight with you? Is there ANYTHING funny about the story or ANYTHING the owner says? Does he strike you as a squid? Is his garage a disaster? The most trustworthy sellers tend to be boring, older ATGATT guys who live in nice neighborhoods and have a rolling tool chest in the garage.

The Ninjette is pretty bulletproof and can go tens of thousands of miles. Both of these bikes are on the newer side and nicely priced to boot.

Looking at the plastics is a good idea to spot unreported damage, but don't focus too much on them. Plastics are like clothes. What you're interested in is the health of the individual underneath. Pay closer attention to the fundamentals.

Do you see scraped bar ends and lever ends? Scrape marks on the exhaust or rearsets? If so, are there longitudinal scratches? Those are signs of an actual crash. A tip-over will leave a mark but not long scratches. Tip-overs are a non-event. About the worst that happens is the front turn signal might punch a hole in the fairing... I know this from personal experience.

Is everything straight? Have the owner stand the bike up vertical (or, better yet, put it on a paddock stand), stand well back and look at the bike from the front. Are the bars lined up?

Is there any binding in the suspension? Do you detect any slop or hear any clicking from the steering bearings?

With the bike running and in gear, grab the front brake and let the clutch out. Does it slip excessively? You should be able to get the bike to stall easily.

Are there lots of mods? That's actually a caution flag... people who crash bikes often do things like replace levers and exhausts, because those are what gets dinged. When I go shopping, I like to see a bone stock bike that's been cared for by that boring ATGATT guy with the tool chest in his garage.

Is the overall condition ratty, with rusted fasteners, filthy wheels and such? An owner who doesn't keep the bike clean probably doesn't pay much attention to maintenance.

When it runs, do you smell anything funny? See any blue or white smoke? If you stick your finger in the exhaust, does it come out oily or excessively sooty? Look in the oil sight glass... is it cloudy, like chocolate milk? (Black is okay... clear amber means a VERY recent change and that could indicate the owner is trying to hide something.)

When you showed up, was the bike already running or warm? If so it may be hard to start and the owner didn't want you to know that.

A college kid with a CBR600 PLUS this bike is unlikely to pay a lot of attention to maintenance, because he's got more things to worry about. That's a yellow flag for me. "Just got its break-in oil change" but he bought it with 1000 miles on it? The break-in change is supposed to happen at 600, but whatever.

Unlikely he's worn it out in only 2800 miles. Unlikely he did a lot of burnouts on it because, well, CBR. If you wanted to do a burnout which one would you pick?

Unlikely the sprockets are shot even if the chain wasn't lubed. Not enough miles. And surface rust is no big deal, but it is a warning sign. Are there any kinks?

The other owner made a point of saying he keeps it on a battery tender, which may or may not be true, but that's an indication that maintenance is at least on the radar. Keeping it on the tender 24/7 is overkill.

How many miles on that bike? Valve adjustments come due at IIRC 7500.