I need help with somthing. I own a 2000 400ex and i run GN4 10-40. It burns in a day or so. My friend has a 400ex and he runs mobil1 and he said it workd great. I run stock jetting(155) and i have a uni filter.

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Mobil1 15-50 synthetic was recomended to me by many people. I bought some but don't know how it works because I haven't been riding due to way too much snow. Try Mobil 1.