First, make note of the exact source of the leak.
You'll need to take off the gas tank and airbox to adequately access the valve cover. The valve cover is held in place by 8 Allen-head bolts. Remove these bolts and the rubber washers. The valve cover may be a little hard to get loose. If this is the case, very carefully pry it up with a dowel or handle of a wooden or plastic-handled tool. The valve cover gasket may or may not come out with the cover. More than likely, part of it will stick to the valve cover and part to the engine. Carefully work it loose and inspect it. If your valve cover is leaking, it's most likely because the gasket is old and brittle, torn, or both. If the gasket is still soft, pliable, and not cracked anywhere, the leak may be coming from one of the bolts or washers. Replace anything that is damaged.
For all years:
- The valve cover OEM part number is 4BR-11191-00-00.
The valve cover gasket OEM part number is 4BR-11193-00-00.
The rubber washers' OEM part number is 5EA-1111G-00-00.
The bolts' OEM part number is 90109-066F0-00.
Finally, very carefully reinstall the valve cover gasket, the valve cover, the rubber washers and bolts. Torque the bolts to 86 in-lbs. This is very important. They bolt directly into the brackets that hold the cams in place and overtorquing WILL break the brackets. Needless to say, this is a major problem and may cost you a lot of time and money to replace.