>50k - My Valve Clearances - Yamaha R6 Forum: YZF-R6 Forums
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post #1 of 10 (permalink) Old 05-23-2019, 06:06 PM Thread Starter
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Post >50k - My Valve Clearances

Specification: (2008 R6S)
Exhaust - 0.23 ~ 0.30mm / 0.0091 ~ 0.0118in
Intake - 0.13 ~ 0.20mm / 0.0051 ~ 0.0079in

Measurements: (1st Number slides right in ~ 2nd Number is Too Thick to Fit)

Cylinder 1
Exhaust -
  • Left Valve: 0.254 ~ 0.279
  • Right Valve: 0.254 ~ 0.279
Intake -
  • Left Valve: 0.178 ~ 0.203
  • Right Valve: 0.178 ~ 0.203

Cylinder 2
Exhaust -
  • Left Valve: 0.254 ~ 0.279
  • Right Valve: 0.254 ~ 0.279
Intake -
  • Left Valve: 0.152 ~ 0.178
  • Right Valve: 0.178 ~ 0.203

Cylinder 3
Exhaust -
  • Left Valve: 0.305 ~ 0.330
  • Right Valve: 0.305 ~ 0.330
Intake -
  • Left Valve: 0.152 ~ 0.178
  • Right Valve: 0.152 ~ 0.178

Cylinder 4
Exhaust -
  • Left Valve: 0.254 ~ 0.279
  • Right Valve: 0.254 ~ 0.279
Intake -
  • Left Valve: 0.152 ~ 0.178
  • Right Valve: 0.152 ~ 0.178

These are initial measurements. Don't expect them to change but as the saying goes, "measure twice, cut once".
...and measure again.

Last edited by Intuit; 05-23-2019 at 06:16 PM.
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post #2 of 10 (permalink) Old 05-25-2019, 01:56 PM Thread Starter
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Re: >50k - My Valve Clearances - Re-shim?

Specification: (2008 R6S)
Exhaust - 0.23 ~ 0.30mm (0.265mm)
Intake - 0.13 ~ 0.20mm (0.165mm)

It appears that only exhaust on 3 is out of spec.
The only single valve readings that differ from others are exhaust left valve on 4, and intake right valve on 1 and 2.

What'd you think? Should I re-shim? This hasn't been touched in over 50k.
Would I be safe, calculating shim size on the median versus what slides in?
Anticipating that the gap widens with wear, should I go ahead and (if possible/practical) res-him all toward the lower end of the specification?
Last question, is there a standard pad size that goes in from the factory, or does the factory potentially use a different shim on all valves?

===============

Second round of measurements...

* First number slides in.
* Second number is too big to fit.
* Third number is the approximate median between the two.

===============

Cylinder 1
Exhaust -
Left Valve: 0.254 ~ 0.279 (266)
Right Valve: 0.254 ~ 0.279 (266)

Cylinder 2
Exhaust -
Left Valve: 0.254 ~ 0.279 (266)
Right Valve: 0.254 ~ 0.279 (266)

Cylinder 3
Exhaust -
Left Valve: 0.305 ~ 0.330 (317)
Right Valve: 0.305 ~ 0.330 (317)

Cylinder 4
Exhaust -
Left Valve: 0.279 ~ 0.305 (292)
Right Valve: 0.254 ~ 0.279 (266)

===============

Cylinder 1
Intake -
Left Valve: 0.152 ~ 0.178 (165)
Right Valve: 0.178 ~ 0.203 (190)

Cylinder 2
Intake -
Left Valve: 0.152 ~ 0.178 (165)
Right Valve: 0.178 ~ 0.203 (190)

Cylinder 3
Intake -
Left Valve: 0.152 ~ 0.178 (165)
Right Valve: 0.152 ~ 0.178 (165)

Cylinder 4
Intake -
Left Valve: 0.152 ~ 0.178 (165)
Right Valve: 0.152 ~ 0.178 (165)

===============


.

Last edited by Intuit; 05-27-2019 at 04:59 PM. Reason: Added ""; Added median value for Specification.
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post #3 of 10 (permalink) Old 05-25-2019, 08:02 PM
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Re: >50k - My Valve Clearances

Most of the time, the clearances tighten with time. The wear mechanism isn’t typically from friction between the lobe and the bucket. It’s the base of the valve trying to hammer itself deeper into the valve seat, which lets the stem rise closer to the lobe. I would look around the #3 exhaust cam loves for any signs of lubrication issues. It does happen that clearances do grow occasionally, but that is normally an indication of abnormal wear. It may not be too concerning after 50k miles, but it’s worth a look.

I always set valves on the high side of the spec.
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post #4 of 10 (permalink) Old 05-26-2019, 01:10 PM Thread Starter
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Re: >50k - My Valve Clearances

Thanks for the input/information.

That's really interesting that the gap ordinarily narrows, instead of widens. Have there been any cases of valve seats loosening or dropping?

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Searches say no.

Since it seems that the clearances can go either way, my guess is the factory shims for the middle of the spec?
Exhaust median = 0.265mm
Intake median = 0.165mm
So all but those five clearances are pretty much right where they should be... after over twice the mileage that the manual recommends?

Cylinder 3 exhaust cam lobes and top of buckets look like the others. The internals are really clean. No visible buildup anywhere. I'm not sure why the clearances on 3E are so different from than the others. I've noticed that the manual instructs to use cylinder three as a reference when syncing vacuum on the remaining three (1, 2 and 4) throttle bodies. In other words we're not supposed to adjust three at all. Coincidence?

I'll be curious to measure and compare cam lobes, along with shims.
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post #5 of 10 (permalink) Old 05-26-2019, 02:09 PM
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Re: >50k - My Valve Clearances

yep they always get tighter. and it's almost always an exhaust valve that needs adjusting.

as far as using #3 as a reference that's just what they more than likely randomly chose for that engine. my R1 says go with the one with the white paint mark. no reference to cyl numbers.
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post #6 of 10 (permalink) Old 05-27-2019, 04:54 PM Thread Starter
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Re: >50k - My Valve Clearances

@
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- Thanks for the reply and information.

Quote:
Originally Posted by 8Ball View Post
............ I would look around the #3 exhaust cam lobes for any signs of lubrication issues. It does happen that clearances do grow occasionally, but that is normally an indication of abnormal wear. It may not be too concerning after 50k miles, but its worth a look.

I always set valves on the high side of the spec.
Kind of a mystery.

I measured the lobes' on cylinder 3, both axis, and they matched cylinder 2 perfectly. Buckets are the same as well. The installed shims measure +/- 0.017 of their stamped value.

To note, three other gaps (4EL, 1IR, 2IR,) are slightly wider. Feeler gauges aren't precise enough to determine if any have narrowed, but going by the median between what does and doesn't fit, none have significantly narrowed, if at all.

It's just that 3EL and 3ER are significantly different. Original shims for 3E are 0.04 thicker than 4E. Replacement shims for 3E are 0.05 thicker than 4EL.


Quote:
Originally Posted by Intuit View Post
........ is there a standard pad size that goes in from the factory, or does the factory potentially use a different shim on all valves? .......
No. The factory installed shim values can be different from one valve to the next. At least on my engine, the values do match per cylinder. So for example, both 3E shims are identical. To note, the factory installed shims are not rounded to the nearest 0.05mm. Some for example some are 184, 188, 191.
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post #7 of 10 (permalink) Old 06-04-2019, 02:37 PM Thread Starter
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Re: >50k - My Valve Clearances

I calculated for median spec. Post assembly, everything was at or below minimum spec.

Nice. /sarcasm

So, I'm now calculating for maximum spec, in order to get median.
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post #8 of 10 (permalink) Old 06-04-2019, 03:31 PM
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Re: >50k - My Valve Clearances

Quote:
Originally Posted by Intuit View Post
I calculated for median spec. Post assembly, everything was at or below minimum spec.

Nice. /sarcasm

So, I'm now calculating for maximum spec, in order to get median.
Did you measure the shims that were in it, or just rely on the number that was printed on it......before 50k miles were put on it? You should always measure the shims with a mic, or digital calipers to determine the actual size.

FYI a 285 shim is 2.85 mm


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post #9 of 10 (permalink) Old 06-04-2019, 03:36 PM Thread Starter
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Re: >50k - My Valve Clearances

Yep, the shims were measured.

If you fudge a decimal, your results won't even make sense.
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post #10 of 10 (permalink) Old 06-04-2019, 03:47 PM Thread Starter
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Re: >50k - My Valve Clearances

BTW, the manual has a chart of pre-calculated values for shim replacement. For 3EL and 3ER, my calculations matched that chart. That lends to the idea that maybe the factory sets them at the low end of the clearance spec, in anticipation of them widening with mileage. I'm not saying that's what happened, just pointing out that it would make sense, given what's been observed in this case. Perhaps just about all widened about the same, except for 3EL, 3ER widening significantly more.
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