Yamaha YZ250 combustion chambers Chamber Selection:Y22 - 20.1cc (100+ octane) Phathead Kits include a head

Phathead Kits include a head shell with one combustion chamber

Kawasaki KX500 Phathead cylinder head kit with compression release 1988-2004

W21 -  21

KTM/Husky/GASGAS screw on and quarter turn gas tanks

Yamaha YZ250 combustion chambers Chamber Selection:Y22 - 20.1cc (100+ octane) Phathead Kits include a headChamber selection: 1999 2022 Y20 22cc Stock compression for the X model Y21 21. 1cc Stock (91+ octane) Y22 20. 1cc (100+ octane) Y23 19. 1cc (105+ octane) 1999 2022 big bore chambers: YZ295 24. 8cc 72mm 93 octane Revised squish clearance . 055" YZ296 24cc 72mm 100 octane Revised squish clearance . 055" 1988 1998 Y30 stock Y31 (95+ octane) Y32 (100+ octane) Y33 (105+ octane)