Loud tapping sound, loss of power or just a tune up. Valve adjustment is a part of most Honda 30/60/90k upkeep, even more so if you rave them. Honda uses an adjustable valve that allow rockers and cams to last much longer then a non adjustable rocker. The reason for this is the adjustable rockers allow clearances to be reset as the metals wear down over time. The down side is hard driving, lack of proper maintenance and bad oil can cause the adjustments to come out of place. Luckily its an easy fix and here how to do it.
First make sure the engine is ice cold, the temperature affect the adjustment, so leaving the car sit overnight is best. Remove your valve cover (ours is a single over head cam). The green circled rockers are the intake and red exhaust. This is easy to tell since each is on the side related to the function. Each side has its own gap clearance, to find this you can google search it, or purchase a Haynes Manual from Autozone like we did. Our car use a .005 intake and .007 exhaust clearance for maximum performance.
Starting at top dead center (you can see the UP clearly marked) check to see if #1 rocker as play in it. because of the design, Hondas are simple to make the adjustments seen below. As you make each adjustment rotate the engine counter clockwise to move to the next cylinder. Consult the Haynes manual again to check the firing order, this will determine what cylinder to do next after the #1
To adjust the valve, loosen the 12mm nut on the rocker arm, slide in the feeler gauge at the proper thickness and tighten the screw until you feel slight drag on the feeler gauge. Once you feel the slight drag, tighten the bolt while holding the screw in place. This lock the adjustment in. Double check your clearance with your feeler gauge to make sure you clearance is correct. Do both intake and exhaust on each cylinder before moving on the next. And that's it, adjustment finished.
I suggest replacing the plug and valve cover seals when doing this. Its only about $20 at Autozone and will save you time and hassle later, as this is a common spot for oil leaks causing fowled plugs, bad coil and other un-fun things.