Owned since Feb 2006
Only that has let me down was the alarm, kept immobilising the bike and giving lots of false alarms. Have had this replaced and has been fine since. Wont be using Acumen alarms in the future, will stick to Meta systems.
Moved on to this from a SRAD600, in my opinion the 2 bikes couldn't be more different even though they're from the same stable. Where as the SRAD is a short lardy ar*e bike the K4 is quite supermodel like in comparision. It's slightly taller so shortar*e's may struggle to get a leg over but it's lighter and thinner so once you're on its a lot easier to throw around. Saying that though it is still a comfy bike, the seat is nicely padded, the pegs at the right height (for me anyway, 5' 11") and a decent reach to the bars, racy but not extreme. The original screen had to go in exchange for a DB, on my first ride home my head was getting ripped off with the wind blast!!!! As with any bike get some crash bungs as well.
Suspension wise - it's there and fully adjustable, mine is on the factory settings which you may find too soft for hard riding. I don't understand all this compression and rebound malarky but I know it's too soft for the track so will get it adjusted on my next trackday.
Brakes - You pull the lever, the bike stops. You pull it too hard, you'll go over the bars!!! Do radial brakes really make a difference to the everyday rider??? Not to me but they look good!!
Engine - It's always started first time and never let me down, pulls strongly from 3-4k rpm right to the redline. Good for a indicated 160mph (on a private test track of course). Decent amount of midrange as well allowing you to be lazy with the 'box.
Gearbox - It's a Gixxer, best gearboxes on the planet!!!
I love my bike!!! Plan to keep it for another year but only because I'll want more power, even then I plan to stay in the GSXR family with poss a K6 750. Its done whatever I've asked of it, whether thrapping round a track, bimbling round country roads or got me home in torrential rain. It's never let me down apart from the alarm which is an aftermarket thing, it's got the power when you need it, the brakes are fantastic, it doesn't cripple you each time you get on it. It's built my confidence up a lot and when it goes it will be missed!