Valve Clearances tightening

[bflint]

My exhaust valve clearances have tightened over time to the point they are at the minimum recommended clearance of .010. I thought they should loosen instead of tighten. Does anybody have any thoughts on this? Also, am I over expectant to think that the dealer/mech should have adjusted the Exhaust valves to their mid value of .011?

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Honda Mfg Clearances (Ex spec: 010-012, In spec: 005-007)
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10/18/2016 Mileage = 11,532
#1: Ex 012-012, In 006-007
#2: Ex 011-011, In 006-007
#3: Ex 012-012, In 007-007
#4: Ex 012-012, In 006-007
Note: 1st check.
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8/4/2018 Mileage = 29,181
#1: Ex 28-28 (011-011), In 18-18 (007-007)
#2: Ex 28T-28 (011-011), In 18-18 (007-007)
#3: Ex 28-28 (011-011), In 18-18 (007-007)
#4: Ex 28L-28 (011-011), In 18-18 (007-007)
Note: Exhaust a little tighter. Intake a little looser.
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3/17/2020 Mileage = 42,500
# All: Ex 010, In 006 } Service Dept front desk lost details
Note: All much tighter. Exhaust clearances at minimum tolerances.

 

[Inhouse Bob]

I'm interested to hear from the experts on this one. I've always been curious about how valves get outta whack.

 

[pekingduck]

The common thinking is that valve clearance clearances increase as cams and bearings, shims, and rocker arms wear. And it's true to a small extent. But the clearances usually come from valve seat inserts in the head getting their sharp edge surfaces constantly hammered by the edges of the valves. Over the long haul, the valve seats will get wider and the valves will lose shape, becoming "tulip" shaped in extreme cases.

 

[peterbaron]

If valve clearance is set perfectly = in the middle of its min and max tolerance by bucket/shim from the very beginning, good quality material, proper oil/intervals and fuel additives are used, there is very small chance that valve clearance will go out of specs. It does not mean skipping valve clearance checks.

Valve clearance set by screw/nut requires more frequent adjustments.
Hydraulic lifters, another story...

In general, most common failure are; wear, carbon build up around valve stem/ seat/lip, defect/failure, abuse, improper maintenance and unqualified personel servicing your engine.

 

[max]

Interesting to hear from someone who has extensive experience with valve clearance.
Nice insight Pekingduck

There may be a reason why new camshaft lobes are ground but not as fine as the bearing surfaces from new,
they may want them to wear some off on purpose and widen the gap as compensation for when the seats wear in and close the gap.



A major improvement over the old adjustment screw system;



Here is a link to a forum that describes what happens when valves wear to the point of no clearance and what the repair turned out to be;
R6 engine troubles at 10k miles;dealing with Yamaha USA

This is why like peter said we keep an eye out and check with practical intervals ( spreadsheet ) for our bikes.

There is a small risk involved when taking the camshafts out and may not outweigh the benefit depending.....
Just my un-educated thoughts,thanks Bflint.

 

[Gone in 60]

For this reason, when my Bonneville hit 12k and I did its first valve check, I set them all toward the wider side of the range. Three valves were under spec at that point. I figure with the tendency for clearance to tighten over time, I would buy some mileage before they would need to be adjusted again.

As to the risk of removing the shafts, of course I dropped an alignment pin into the engine, so the thought of not having to do that again is welcomed.

 

[dave]

As to the risk of removing the shafts, of course I dropped an alignment pin into the engine, so the thought of not having to do that again is welcomed.

How did you get that alignment pin out?

 

[zirconxi_imp]

Interesting to note that the valve usually get tighter as mileage climb. The 1st time I check, my CB had been on the loose end limits and wondering will it get more loose or more tight, but riding privileges had been scarce lately and I can't clock enough mileage for next check.

When clearance getting smaller, will it make the top quieter or louder? Some old mech told me when valves clearance is out of spec, there will be baby bird chirping sound... But i read in some motorcycle forum and they claim tighter valve will be more quieter hence can't know when its too tight until too late..

 

[Gone in 60]

Dave- I put RLETs on the Bonneville and the pin floated back up the breather tube by itself.

 

[LakeWylieJoe_imp]

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.

 

[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.hy:

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.