I just bought a 2003 400ex with 2nd gear gone. I am running a 440 kit in my 2000 400 with sparks cam, mx head, x6 pipe, WB cdi, FCR 39. I need more power and lots more torque since I am spliting the cases I am thinking of a stroker motor. I see most threads are 416,426 and 440. I am looking for info on something bigger , like a 465 or 505. Any info or sites that may be any help would greatly be appreciated.

 

do a search on exriders.com there's lots of good info on there. Sparks and Trinity make some nice 465's.

I think...
416cc bore+stroke=440cc

440cc bore+stroke=465cc

465cc bore+stroke=505cc