Just adjacent to the oil filler cap on the engine there should be cast into the cover the amount in cubuic centilitres (CC), there are usually two ways to measure the oil level on smaller capacity motorcycle engines, 1) A Dipstick which is part of the oil filler cap and you just place, not screw in, into the aperture and then read off the level toward the bottom of the stick, it is usually marked MIN and MAX or 2) a sight glass on the side of the engine, perhaps quite hidden away from casual view, again marked with two lines for MIN and MAX. anywhere between these two lines is fine. The engine must always be switched off and it is best to place the Motorcycle vertical and then check, if it is on the prop stand the angle of the lean will give a false reading, also when checking the oil the engine must be off and the oil needs about 5 minutes to flow back down to the sump after its been running.

A small engine such as a rebel will NOT require more than 3 litres of oil, including filter change if that, however a Honda dealer should be able to give you a presice quantity.