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Valve clearance slighty off. Should I worry?

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hornet_guy
Two Stroke Sniffer



Joined: 24 Jan 2021
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PostPosted: 17:57 - 14 May 2021    Post subject: Valve clearance slighty off. Should I worry? Reply with quote
Hello,

I checked the valve clearances of my 2000's Hornet 600 for the first time and discovered 3 out of 4 cylinder exhaust valves (6 valves) are off. The workshop manual indicates 0.22 +- 0.03 mm and I measured around 0.28 mm in all of the 6 valves. I know this is out of spec, however I'd like to know, in your experience how bad is this. Should I worry? How much would you say is too much?
Thank you.
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Pete.
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Joined: 22 Aug 2006
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PostPosted: 18:12 - 14 May 2021    Post subject: Reply with quote
That would not bother me at all. Too tight would be a concern, too loose not so much.
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132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy
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jaffa90
World Chat Champion



Joined: 06 Apr 2016
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PostPosted: 18:14 - 14 May 2021    Post subject: Reply with quote
Pete. wrote:
That would not bother me at all. Too tight would be a concern, too loose not so much.

I agree,
https://www.manualslib.com/manual/1068381/Honda-Cbf600sa.html?page=79#manual
The CBF 600 SA is the same as your reading.
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hornet_guy
Two Stroke Sniffer



Joined: 24 Jan 2021
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PostPosted: 18:17 - 14 May 2021    Post subject: Reply with quote
Pete. wrote:
That would not bother me at all. Too tight would be a concern, too loose not so much.


Hmmm, really? Take into account that in my bike (shims) the greater the gap, the tighter the valve is. Does this change your answer?
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Pete.
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Joined: 22 Aug 2006
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PostPosted: 18:26 - 14 May 2021    Post subject: Reply with quote
hornet_guy wrote:
Pete. wrote:
That would not bother me at all. Too tight would be a concern, too loose not so much.


Hmmm, really? Take into account that in my bike (shims) the greater the gap, the tighter the valve is. Does this change your answer?


Nope. when we refer to valves being 'tight' it's the gap we're referring to not the closing pressure. A tight gap (less clearance) shortens the time the valve is seated thus reducing thermal transfer from the valve head to the seat. A loose gap allows for greater cooling and longer valve lifespan.
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132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy
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Nobby the Bastard
Harley Gaydar



Joined: 16 Aug 2013
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PostPosted: 18:46 - 14 May 2021    Post subject: Reply with quote
hornet_guy wrote:
Pete. wrote:
That would not bother me at all. Too tight would be a concern, too loose not so much.


Hmmm, really? Take into account that in my bike (shims) the greater the gap, the tighter the valve is. Does this change your answer?


Thats so wrong. You have it completely back to front.
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hornet_guy
Two Stroke Sniffer



Joined: 24 Jan 2021
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PostPosted: 18:57 - 14 May 2021    Post subject: Reply with quote
jaffa90 wrote:
Pete. wrote:
That would not bother me at all. Too tight would be a concern, too loose not so much.

I agree,
https://www.manualslib.com/manual/1068381/Honda-Cbf600sa.html?page=79#manual
The CBF 600 SA is the same as your reading.


That's a good point for reference, although it's not the same block. Thanks.
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hornet_guy
Two Stroke Sniffer



Joined: 24 Jan 2021
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PostPosted: 19:00 - 14 May 2021    Post subject: Reply with quote
Pete. wrote:

Nope. when we refer to valves being 'tight' it's the gap we're referring to not the closing pressure. A tight gap (less clearance) shortens the time the valve is seated thus reducing thermal transfer from the valve head to the seat. A loose gap allows for greater cooling and longer valve lifespan.


Thanks for the detailed explanation. It makes all the sense.
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hornet_guy
Two Stroke Sniffer



Joined: 24 Jan 2021
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PostPosted: 19:02 - 14 May 2021    Post subject: Reply with quote
Nobby the Bastard wrote:
Thats so wrong. You have it completely back to front.


Yeah, sorry you're right.
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droog
Spanner Monkey



Joined: 03 Dec 2019
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PostPosted: 20:24 - 14 May 2021    Post subject: Reply with quote
hornet_guy wrote:
Nobby the Bastard wrote:
Thats so wrong. You have it completely back to front.


Yeah, sorry you're right.



If you're interested in this kind of stuff, check out this video on valve clearances - the guy uses a model to explain the relationship between cams, buckets, shims and valves and what creates a tight/loose valve condition.

Good way to visualise what is going on.

https://www.youtube.com/watch?v=Ou_3Qo8wTec
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MCN
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Joined: 22 Jul 2015
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PostPosted: 21:35 - 14 May 2021    Post subject: Reply with quote
If there is no gap between the top of the valve stem and the valve drive (cam linkage) then the valve will not seal effectively.
If not sealing effectively then cylinder compression is reduced.
Reduced cylinder compression reduces engine power.

High power from internal combustion engines rely on high cylinder compression.

This is the main symptom of tight valves.

In addition, contrary to what some folk imagine, as the engine runs and wears the gap is reduced.
Until zero gap.
It also can have a minor effect on timing.
How well a cylinder is charged with fresh air and then purged of exhaust.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.
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hornet_guy
Two Stroke Sniffer



Joined: 24 Jan 2021
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PostPosted: 22:29 - 14 May 2021    Post subject: Reply with quote
MCN wrote:
If there is no gap between the top of the valve stem and the valve drive (cam linkage) then the valve will not seal effectively.
If not sealing effectively then cylinder compression is reduced.
Reduced cylinder compression reduces engine power.

High power from internal combustion engines rely on high cylinder compression.

This is the main symptom of tight valves.

In addition, contrary to what some folk imagine, as the engine runs and wears the gap is reduced.
Until zero gap.
It also can have a minor effect on timing.
How well a cylinder is charged with fresh air and then purged of exhaust.


Thanks. I am very inclined to leave it alone after all the comments. If the wear produces tighter clearances then I think, I won't bother with the pain of reshimming.
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