Got a buddy who picked up a used 450.......kind of a war horse.....raced pretty hard. He's got it all torn down for new parts...linkage bearings, headset bearings etc. The bike ran well before he took it all apart. The only thing that is left intact is the motor in the frame..... The question is the previous owner said he adjusted the valves what we want to know is do these bikes have any history of valve problems. I know two guys with 00 426s that are stone reliable. While we have the bike torn down this far should the valves be replaced or maybe just check the clearances, do a compression check and ride. I looked through the open slide and the intake passage and valves looked pretty clean in there. Any help would be appreciated.