I pretty much abandoned the Honda service manual and just used this guide solely. I like the older Honda manuals, but this one has too much back and forth, referring to other sections. Page 3-8 might say, "Remove widget; refer to page 12-6." You go to 12-6, and it says, " Remove watchamacallit; refer to page 3-6." And so on.
I approached this task yesterday at 14,000 miles, since I would be on a trip next month which would take me beyond the 16K mile service interval by at least a couple thousand miles. One thing I want to mention, which I haven't really heard yet, is how critical it is to use a proper width feeler gauge. I finally found locally a set of angled feeler gauges with .001" increments. I measured the intake valves at about .006", which is right on target. I measured the two exhaust valves at .006" & .008". Dutifully, I dove into doing the calculations to calculate the proper replacement shim, not stopping to think logically that this measurement would mean the valve tightened up by half! Something would be seriously amiss if this were the case, but I was confident of my measurement, and focusing on doing the math correctly and not fvck that up. I replaced the shims with the new thinner shims, and when I went back to check the new clearance, I got the same exact readings: .006" & .008".
I knew this was impossible, and that the explanation must lay somewhere in the measurement process. Just then a light bulb went on in my head. When I took the bike in for the 600 mile service and valve adjust, the shop told me the mechanic was having some problem, and had to get on the phone with Honda to resolve it. When I picked the bike up, the vague explanation the front desk guy told me was there was some problem with the feeler gauge, and if the gauge was not used just so, what was actually being measured was not the correct valve clearance. Fast forward to yesterday and my head-scratching identical pre and post-adjust readings.
My feeler gauges are angled, but not tapered. They are typical 1/2" wide gauges. When I had inserted them between shim and rocker fork, it was not a smooth feeling, more like it was catching up a bit on the back end of the insertion. The problem is, this is exactly what was happening. The shim is so close to flush with the valve spring retainer, or even recessed (?) that the wide feeler gauge hangs up on the top of the valve spring retainer instead of the shim, and the resultant measurement is that of the gap between the valve spring retainer and the rocker fork. Of course, when I put in the thinner shims, that measurement did not change, hence the identical reading even though I used shims about .005" thinner. You
must use a feeler gauge narrower than the width of the shim, or about 7.48 mm. In this way, you are measuring the gap between shim and rocker fork, because the feeler is not riding up onto the valve spring retainer. The tips of tapered gauges would fit this bill. I happened to have three Motion Pro tappet feeler gauges which are narrow and angled. By doubling and even tripling up on the correct feelers to arrive at the various thicknesses, I was able to get an accurate measurement, although it was very difficult to keep multiple Motion Pro gauges together.
I decided to just start over, by replacing the original shims I had removed. When I did this, and measured the gap with the narrow feelers, the exhaust valves came in at 0.27 mm & 0.25 mm. The original shims did not need changing at 14K miles! I wonder how many people may have used a typical wide feeler gauge on an exhaust valve and measured .006" or so, put in shims .005" thinner, then buttoned it up without rechecking the clearance, and ended up with a clearance of .016" instead. It would be so easy to do.