there is no oil tank on this bike. the engine and transmission use the same oil together . on the right side of the engine down by the clutch plate cover there should be a small round window . this is so you can see how much oil is in the bottom of the crankcase.unscrew the oil cap on the top of the clutch cover. then,have someone hold the bike level and add 3 quarts of oil. you should see the oil in the small window. slowly add more oil until there is a small bit of the upper part of the window is not covered by oil.CAUTION,,,DO NOT fill oil past the top of the glass window otherwise you have overfilled the crankcase and you could end up blowing engine seals.replace the oil cap and now you are ready to ride.