In the quest for more power I have tried just about every aftermarket bolt on that there is with very disappointing results....which finally led me to try RHC's FCR carb mod bore. He bores the carb almost 5mm and does it on a different angle to get a better charge into the head. After bolting the carb on I started the bike, set the idle, and then went up the street. (Couldn't wait for the dirt) From the first crack of the throttle my smile started to curl up my cheek bone! This mod is worth way more than the price that he charges. The bike is so much more responsive and revs quicker with much more authority! I brought the bike back and called Ron and thanked him for such a great change to my bike. He gave me a few other tidbits to help the bikes power and ridability. So I implemented them and headed for the dirt with my brothers stocker. It is set up just like mine....same tires same ect. With a GPS strapped to my helmet I did some hillclimb runs with both bikes and always backed up the results at least three times before coming to a conclusion. The RHC carb mod made a 3 to 4 mph difference on every hill. Most of these runs were made in second or third gear! I was really really impressed. A friend of mine bought a KTM525sx and put the big bore and stroker crank in it. A really cool bike. The kit cost well over $1000 and it only increased the speed of the bike by 1mph up these same hills. We tried different gearing and such, but didn't get the bang he was searching for. He will be calling RHC very soon. Any bike with a FCR carb will love this mod. And it makes the bike more ridable especially in slow conditions. The bike feels like it has a flywheel weight it carburates so much better and smoother down low and then when you hit the throttle hard it feels like you just pushed the warp speed button on the USS Enterprise! In side by side drag races, it seems to have increased the bikes accelleration by about a bike length a gear. Very very impressive! A big Thanks goes out to RON HAMP from RHC You can contact him at www.ronhamp.com. This has been the best performance mod for the $ I have ever experienced! And I believe to be a much needed one for the YZ! note* just noticed I posted this in the WR forum and not the YZ allthough this mod will work well on the WR could someone please move this to the YZ forum for better exposure?! Thanks!