GSXR400 known issues?

[leopard_pagan]

A mate of mine is about to buy a GSXR4, he's a compleat novice at the whole bike thing. I own a NC29 & know what to look for on those.
Before we head up to look at this bike, need to know if there are any known issues, niggly things or quirks that nearly all GSXRS do.. Eg: NC30 often have trouble getting back in to neutral, most Hondas have the reg/rec issue.

Ta..

[Marsbar]

Carbs are a pain, had mine off loads to change the 'o' rings. best buying the kit of VVS and give it a good service. had trouble with 2 engines i had with low compression mainly from the valves getting carboned up. mine and my mates valve dropped on us rear shock is best being changed with a modern one, mine was a straight swap from a K7 750 gsxr. lovely bikes though miss riding mine already.

[Awynn]

Same reg/rec issues with the GSXR, clutch dragging causing troublesome gear changing/neutral finding, as said o-rings in carbs causing rich running unless been done already, cam tensioner can lets go, failed headlight switch from high watt headlights being fitted without relay mod, failing/failed CDIs.
Apart from tensioner killing engine and CDI problems I have had/do have all of above and seem fairly common.