Well, I've sold a bike on eBay and bought a car from there too.
Firstly - if as you say, it's a bike you really really want - then write your highest bid down on a bit of paper and stick it to your screen! Don't let youself get caught up in the eBay fever and stick to your original goals.
That said - check out the seller, then check out the ad, but do both with a positive attitude rather than a cynical one - otherwise you'll just end up getting grumpy, depressed and suspicious.
If you can get to see the bike then do - and if it's what you want make an offer there and then, it can't hurt.
If you can't get to see it, and you still like what you see in the ad, then bid to a just under your maximum and then watch the auction in it's closing stages. Then if it looks like you'll lose it then within the last 15-30 seconds (depending on your typing speed and internet connection) bid up to the remaining amount of your funds.
Keeping a bit in reserve on an auction like this can make the difference between winning and losing because someone has sniped you with a couple of quid extra.
Take a copy of the ad with you and thoroughly check the bike over before paying. If you find it isn't exactly as advertised then you can either begin to barter the price or walk away.
This is why I say view the listing with a positive attitude as if the advert is missing vital information then according to eBay's own rules you are free to walk away.
The bike I sold was my damaged Ninja. It was only cosmetic stuff and I had picked it up cheap through work to do up as a track bike... then my 'Blade came along.
I must have listed about 15 photos of the slightest little scratch - the guy who won hadn't seen it before hand and said it was a lot better in the flesh than he'd thought. Gave me an extra £50 - so there are nice people out there y'know.
The Mini I bought was a must have emergency buy - knee fecked and needed the cheapest automatic I could get. It was up in Middlesborough so I didn't have a chance to get to see it first - but knew what I had to spend and that was it.
Won it for £550 quid, got a lift up there from a friend (who also followed me back) and found I'd a real bargain as it looked better than it had in the photos.
18months later and I have still to have any problem with it. Great little car and an absolute lifeline.
