Well i own a 2003 WR450F turned into supermoto form. For all those years i kept the engine stock because i didn't want to mess around with the longevity. Just a complete exhaust system (WB carbon pro, open air filter, JD kit and YZ450F exhaust cam). By the way with the YZF cam the bike didn't e-start. A few months ago i decided it was time to freshen the bike a little bit, so i started the search for some big bore options and cams. I didn't get too much info regarding WR450F's so i feel the need to write down my experiences. At first i decided to go with the Ice Cube Cylinder with CP 12:5 piston. The bore of the Ice Cube is 99mm (4mm wider than stock). This translates into 488cc. This is the most you can gain with just overbore. The quality of the cylinder and piston is unbelievable! Installed them, run the bike for 3 hours and WOW. Without changing anything else at all (not even the jetting) the power gains were beyond my expectations. Ok, i was sure that the bike would gain some extra ponnies but i was not prepared for such a difference. It picked up revs faster than before. Not like the big slow revving thumpers way from the extra cc's Just instant response to the throttle with a free revving feeling. And a big power difference down low and into the middle. The thing was that with those extra cc's the power curve moved something like 1.000rpm lower. At first i could feel that the bike liked to be revved at almost 11.000 rpm but after Ice Cube i had to do something to get this feeling again. So i decided to go wild and buy the Web Cams #963 grind. These are very wild profile race cams for mid and upper power gains. Once i installed them i had to change all 5 shims (the intake shims were 10 numbers larger compared to what i had. 190-195!). The sound from the valves changed completely. They now make a rattling noise, which i have to admit was terryfying in the beggining, but now i got used to it. The bike is very hard to kick start and with the stock battery the e-starter won't spin at all. I plan to buy a Shorai battery to fix this problem. As for the power gain....is unbelievable!!! I have the low grunt from the extra cc's, but after that the power pulls forever! It just won't sign out even until i hit the rev limiter. Very impressive! now i want to try some different jetting settings to take the best out of this combination and then go for a dyno measurement!