Yamaha YZ250 2021 Owner's Manual

ENGINE8-8EAM30603CHANGE OF THE HEAT RANGE OF SPARKPLUGSJudging from the discoloration of spark plugs, ifthey are found improper, it can be corrected bythe following two methods; changing carburetorsettings and changing the heat range of sparkplug.• In principle, it is advisable to first use sparkplugs of standard heat range, and judging fromthe discoloration of spark plugs, adjust carbu-retor settings.• If the calibration No. of the main jet must bechanged by ±30, it is advisable to change theheat range of spark plugs and newly select theproper main jet.TIP• When checking the discoloration of sparkplugs, be sure to stop the engine immediatelyafter a run and check.• Avoid racing.• When changing the heat range of spark plugs,never attempt to change it more than ±1 rank.• When using a spark plug other than standard,check its heat range against the standard andcheck that it is a resistance type.• Note that even if the discoloration seems prop-er, it may slightly vary with the spark plug mak-er and oil in use.Standard spark plug BR8EG(resistance type)