If you are thinking of buying it, check for a "rattle" around 2k...that would be the alternator bolt. Start it a few times, w/ and w/o choke to stress the starter/sprag a bit. A loud noise (banging or grinding) could be a sprag clutch failing. Some of the more expert folks have stated that they just fail...so this may not be the best test. The stock GILL coils tend to fail, as does the ignition pickup sensor....PVL coils will fix the coil problem, a spare pickup in the bag "just in case" will fix that problem.
Look for smoke at startup and under accel....if possible, have a friend follow you and watch for any smoke. Roll-on smoke (light) normally indicates valve seal wear; heavy roll-on smoke normally is a oil ring...and you'd get some smoke at idle as well. Mine, at 56K miles, uses no oil and I'm getting 50 mpg....last year at $4/gal. I loved the Strumpet! Hopefully I've covered a few of the items and not made too many mistakes.....
One thing I do like about the Sprint is the "frog-eye" front. Of course, I DID have a Frog Eye Sprite (aka in the US a "Bugeye Sprite") so the look does have an appeal to me. Also, a stinkin' bright set of bulbs tend to light up the road a bit better. I'm running Pirelli Stradas on the bike at present, and will be doing some of the front end mods soon. Oh...a Corbin seat and the taller Rifle screen do help on long rides.
And the triple sound.....sonorous.....
Derswede