2006 Honda TRX680 Rincon Factory Service Manual, Page 87Get this manual
MAINTENANCE This vehicle's spark Check the insulator for cracks or damage, and the plug is equipped electrodes for wear, fouling or discolorationwith an iridium type Replace the plug if necessarycenter electrodeDo not clean the electrodes
INSULATOR
SIDE ELECTRODE Replace the plug if the center electrode is rounded as shownAlways use the specified spark plug on this vehicle
CENTER ELECTRODE
SPECIFIED SPARK PLUG: Standard: IFR5L11 (NGK), VK16PRZ11 (DENSO) For extended high speed riding IFR6L11 (NGK), VK20PRZ11 (DENSO)
ROUNDED ELECTRODE