RM80/85   Kit includes
1 head body, 2 domes, 1 o-ring kit
4 copper washers

1991-2010 Head body

OS9 o-ring kit fits all years same as OEM o-rings

Dome selection (see note)
S01 6.9cc
S02 6.4cc
S03 5.9cc
S04 5.6cc

Dome selection (see note)
Y01 6.4cc
Y02 6.0cc
Y03 5.6cc
Y04 5.2cc

Note
Heads colors are red, blue, black, gold and aluminum
S0 (RM85) and Y0 (YZ85) series domes fit this head body
S0 series domes are similar to stock dome geometry
S01 dome is closest to stock compression
Y0 series domes are 1mm taller than S0 series domes they are popular for big bore motors
S0 and Y0 series domes max bore 54.mm
Dome modification for big bore available see FAQ