My friend just bought a 2003 600. He complained about vibration at higher rpm. I rode the bike today and it does get an engine vibration around 6000 and up. Bike has around 13K. What can we do to make this go away? Valve adjustment? Please help. Also is there a way to make sure the front forks are aligned right. The bike was lowered when he bought it, had lowering links in the back and the front forks where slid up. We put the stock links back on and slid the forks down, just kind of eye balling it. Thanks for any help.