Yamaha Outboard Motors Factory Service Manual F6 and F8, Page 282Get this manual
CAMSHAFT AND VALVES INSTALLING THE VALVE
Install: Intake valve or exhaust valve Valve spring seat Valve spring Valve spring retainer Valve spring lock Valve spring compressor: YM-0125390890-04019 Attachment: YM-0410890890-04108
Set the attachment on to the center of the spring retainerDo not overtighten the valve spring compressor