Valve Clearances tightening

[peterbaron]

^^ THAT ^^ is the most proper valve clearance procedure.

[bflint]

If they are going to charge you full price for the clearance inspection/adjustment job, they should set all valves back to the center of the spec range. If a cam or both have to come out, may as well get things exactly right. I always set my valves to the center of the range so if they drift one way or the other a bit, they'll still be fine.

Hypothetically, if a customer agreed ahead of time with the shop that if any valves were right at the edge of a spec limit (and the rest were within spec) they could be left alone in exchange for a lower cost, that would seem to be okay.

Pulling the cams adds a lot of work to the overall job. Especially since the cam chain isn't long enough to allow the intake cam to come out with its sprocket still installed.

I had one exhaust valve out of spec (loose and ticking) at the first check and none out of spec since then with 30,000mi on the clock now. However, I've swapped at least a dozen shims over the next two checks to bring borderline valves back to the middle of their spec range.

I emailed my original post to the motorcycle shop (El Cajon MotoWorld) and asked for their head mechanics feedback.

[LakeWylieJoe_imp]

I might be more-anal-than-average, but it's nearly as easy to adjust all 16 valves as it is just 1. Why not put them all in the center of the spec range? If one is right at the limit, it could be out of spec by the time you get home.

If you paid for a brake job and the pads were right at their service limit, would the shop send you home that way? it's not a perfect analogy but you see where I'm coming from.

[pekingduck]

If it's in the range, it's within spec. But I think only a particularly conscientious tech would at least put the outliers a little closer, if not necessarily exactly in the center. You can do all the measurements correctly, and still, occasionally, one will not have the expected clearance, meaning you pull the cam again.

I remember adjusting my CBX valves - at least the cams didn't have to come out. I had a good stock of the "in-between" sizes that only came with bikes originally, and it took at least twice as long to get it "perfect".

[max]

Availability of the " half" size shims could be an obstacle, 0,05 mm is the normal step size and 0,06 mm ( + or - 0,03 mm ) is the difference between in and out of tolerance, in other words the valve has to be 0,02 mm out of spec to bring it in just in spec for the other limit unless you have some 0,025 step shims which do enable you to set the valve back close to the center of spec. giving you 3 steps instead of one big one.

Presuming the tech has the ability to measure to 0,01 mm ( not easy )( and most gauges step 0.05 mm anyway ) instead of " in or out " of spec.
And looking at Joe's excellent spreadsheet ( thanks Joe ) that can last a lot of miles before the need to re-adjust the shims depending how you ride.

Not claiming that it is not a good idea but could mean a bit more work and out of spec is not immediately dangerous territory here, ( 2 and 4 x 0.05 mm steps away from zero when hot ) there is a bit of leeway depending.

Edit; never actually tried this but does the gap actually get smaller with a hot engine?

[Houtman_imp]

If it's in the range, it's within spec. But I think only a particularly conscientious tech would at least put the outliers a little closer, if not necessarily exactly in the center. You can do all the measurements correctly, and still, occasionally, one will not have the expected clearance, meaning you pull the cam again.

I remember adjusting my CBX valves - at least the cams didn't have to come out. I had a good stock of the "in-between" sizes that only came with bikes originally, and it took at least twice as long to get it "perfect".

Adjusting the valves on a CBX was easy , just time consuming with with the right ( and cheap ) tools it was no problem . I had bought a non runner CBX and had 24 extra valves , never had to buy new ones. A GOOD micro meter was also a must.

[LakeWylieJoe_imp]

My feeler gauges are stepped in 0.001" increments (roughly 0.025mm), so if the 0.007" feeler goes in the gap easily and 0.008" doesn't go at all, I have to judge how far above 0.007" it is by feel. Since the shim sizes roughly step the same way, there is no way to get exactly to the center of the spec range. I always do my best to get it as close as possible, though, so there is some room for drift either way over the next 8,000mi.

Anyway, it think it's foolish to leave a valve right at the limit of its spec range if you are already have the valve cover off and have your hands dirty.

Of note, I went to a dealer here during the 8,000mi service to see if they would swap some shims with me. My dealer in Rock Hill, SC would do this no charge. The dealer here (Sandy, UT) said they didn't stock any shims... What?!? I asked what they did with the ones that came out of an adjusted head and they guy gave a nervous chuckle and said they are a "wear item" and they throw them away.

These guys likely aren't actually adjusting any valves, but charging for it nonetheless. Why the heck would you throw away shims when the next bike through the shop can use them? The second shop I visited only had every other size so they best they could do is move a valve from being at one extreme of the spec range to the other end. I gave up and ordered a selection of most likely to use sizes and added them to my toolbox.

[peterbaron]

^^ THAT^^ +1

[pekingduck]

I've come across shims (with the size printed on them) that were put in with the marking rubbing on the cam lobe for tens of thousands of miles, and still perfectly legible. Shims just don't really wear, as long as there is a clean oil film.

[LakeWylieJoe_imp]

You are correct. They don't wear, residing as they do below the bucket and above the stem and spring assembly. They merely get squeezed once every other crank rotation, and they are made of very hard metal.
Enclosed is the MS Excel shim calculator I use, if anyone wants to try it. You enter the measured clearances and the installed shim thickness and it calculates the new shims needed. It's laid out like the valves are in the head so you can keep all the numbers organized.

You can always copy and paste the calculations lower on the page each time you do a service so you have a record of what each valve does over time.
Let's try that again. The spreadsheet previously sent wasn't ready for prime time. This one is.