G´day i bought an 06 klx 250 bout a month ago and for the first week it was alright, until i got used to it, then i discovered how gutless it was due to it being so restricted. if you find this out to it will have to be de-restricted. it takes some work to de-restrict them but it can be done for that extra bit of punch. the top of the air box has to be removed, the carbi slide has to be removed and can be replaced for $360 if you dont have that type of cash just block of the 2 holes that sit together (devcon is the best to use) do not block the one by itself. the carbi will have to be re-jetted this will cost about $85 from your dealer. and for the best performance a straight through muffler is the best.All i did was get a piece of 3 inch stainlesswith a cap on each end and a peice of perferated tube bout 1.5 inches dia then packed the space between the to with muffler packing works a treat. the next mod will be an 11 tooth front sprocket for that extra pick up. let you know how it goes.