Mate, who gives a shit..........
If ya can't tell a good un from a bad un get someone else to buy your bike for ya.
A modded bike, if done well and it is cherished by the owner is probably the best bike to pick up.
Buy a stocky and it may have only just got a good wash and a set of rubber recently, ran with no services, unless proof can be presented and a guy that does his own mods usually does them to improve the look of his pride and joy.
The only thing I get wary of is polished frames and swingarms on the newer bikes, why? crash damage usually, even a scratch or gouge in a frame or swingarm can put even the most interested buyers off.
But rearsets, screens, indicators, zorsts,jet kits, k&n etc etc, great even better if origanals are supplied.
Wish some bastard had gone to the trouble to fit Ohlins suspension to my '9 before I had bought it
Oh and as for modded bikes, I wouldn't turn my nose up to MadKaws 10 if it came on the market and thats been on its side AND been modded, and I'd pay market(mates rates) price for it, just goes to show there are people that can and people that can't.
Like I said, do ya homework, if the bikes been owned a couple o years, piccies from before any mods, genuine seller, original parts you aint gonna loose, ya only gonna win.
Stay away from the dealers on second hand bikes, they'll only get the machines that someone else can't(or can't be assed to)sell and very rarely you get nice aftermarket goodies.
Good luck with ya huntin