So heres a quick run down. I graduated from Uni 18 months ago and as a grad present i bought a 2003 WR450FR. Yay me! Anyhows, after a full $450 service and going over by the local Yamaha dealer i bagan riding. After only riding it 3 times, i found out (the hard way) that i had a blown head gasket. Turns out I had a siezed head, busted valves and enough imprints on the top of the piston to make a grown man cry. So i started pulling it down for the rebuild. Now with a tight budget and a small amount of mechanical knowledge i'd like to get it up and going again! I've sorced a reasobably priced complete ported and polished serviced head for a YZ450FS (04) which i've been told is the exact same print as the wr head. Only differences being cams and maybe valves (correct me if im wrong). The head gasket is definately the same according to yamaha so i should be heading in the right direction. I didnt aim to use YZ parts but they were cheap and now will hopefully save me money. My questions are: Is the crank the same on YZ/WR? Ie do i need to change to the yz one to maintain the use of the YZ cams etc? I know the stroke bore and compression ratio is exactly the same between the wr/yz (according to yamaha) but is the crank lighter on yz? Do i need to change cam sprockets to run yz cams? YZ cam chain etc? And finally im assuming i'll have to change jetting etc to get this all to run properly together? I've heard the enduro guys use YZ heads on wr's all the time but havent seen any write ups etc that may point me in the right direction. Any help in this area would be grealty appreciated. I phoned a few local yamaha dealers and i cant get a straight answer from anyone whos done this before. only bits and pieces that im trying to put together. thanks.