Valve adjustment questions

[GoSlow2GoFast]

I'm in the process of doing this adjustment on a Triumph Daytona 675 currently, and will likely be doing it on the GSXR at some point in the future. As i'm working through it I have a couple of questions.

(1) Over time, is it typical that the measured clearance will decrease, or increase? Also, what are the factors that contribute to this, I can think of a few factors that can contribute, but not sure which ones truly are at work, like: valve seat wear, valve stem stretch, valve shim wear, cam lobe wear, cam bearings wear...

(2) When a measured clearance is out of spec, and therefore a new shim will be swapped in, what's the preferred place in the acceptable range to target? Should a shim be selected that would get the clearance closest to the middle of the acceptable clearance range? Or is it better to fave the higher, or lower, end of the acceptable range, planning for future effects?

(3) When using the feeler gauge to measure the current clearances, how hard should the feeler be "forced' between the cam and the bucket? Since it's on a little bit of an angle you can't get a straight shot with the feeler into the gap, so it takes a little pressure to get the feelers into the gap, just wondering how firm that pressure can be? Is it true that as long a feeler can be pushed between the two surfaces then that's a representation of the gap, or could too high a gap be measured if a feeler is "forced" in? I'm thinking it wouldn't be possible to be lifting the valve just by pressing the feeler gauge in, but looking to validate that assumption.

Thanks for any insight to these questions.

~gs2gf

[Kurlon]

1) Normally valves will tighten up as the valve seat and the valve itself beat themselves to death against each other.

2) I shoot for the 'loose' end of the spec knowing the clearances will tighten over time.

3) What you're looking for is a bit of drag once the feeler is in there. The feeler will 'stutter' as you pull it back when the drag is right. If it just slides go up a size. Heavy drag, go down a size.

[Cerberus]

1) Normally valves will tighten up as the valve seat and the valve itself beat themselves to death against each other.

2) I shoot for the 'loose' end of the spec knowing the clearances will tighten over time.

3) What you're looking for is a bit of drag once the feeler is in there. The feeler will 'stutter' as you pull it back when the drag is right. If it just slides go up a size. Heavy drag, go down a size.

on all

[stoinkythepig]

1) Normally valves will tighten up as the valve seat and the valve itself beat themselves to death against each other.

2) I shoot for the 'loose' end of the spec knowing the clearances will tighten over time.

3) What you're looking for is a bit of drag once the feeler is in there. The feeler will 'stutter' as you pull it back when the drag is right. If it just slides go up a size. Heavy drag, go down a size.

I wish I could add something, but you covered it all perfectly.

[Degsy]

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Kurlon for prez. I would add that you should use angled feelers, they work better.

[Manny]

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Ahh love the angled feeler.

[Degsy]

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Ahh love the angled feeler.

Straight feelers are soooo 20th century.

[intergalactic]

1) Normally valves will tighten up as the valve seat and the valve itself beat themselves to death against each other.

2) I shoot for the 'loose' end of the spec knowing the clearances will tighten over time.

3) What you're looking for is a bit of drag once the feeler is in there. The feeler will 'stutter' as you pull it back when the drag is right. If it just slides go up a size. Heavy drag, go down a size.

I am of the opinion that you should be on the tight end of the range if you are racing, as the forces (that accelerate the valve open) on the cam are pretty brutal if the gap is larger rather than smaller. And of course you will be checking valve clearance much more often if you are racing, right? You can also slightly increase the duration on a stock cam that way. Again, only if you are racing.

[stoinkythepig]

I am of the opinion that you should be on the tight end of the range if you are racing, as the forces (that accelerate the valve open) on the cam are pretty brutal if the gap is larger rather than smaller. And of course you will be checking valve clearance much more often if you are racing, right? You can also slightly increase the duration on a stock cam that way. Again, only if you are racing.

You are correct. Increases lift a smidge too.

[Stromper]

:iws: all

Try to practice the feeler gauge thing a few times before you write down the number

Make sure you have a good set of feeler gauges you will be in the 0.003 to 0.010 range.

You can find a few shims you can swap with other valves espescially if you have a micrometer so you can measure them. When I had a surface grinder I just ground down them to the "new" dimension

Use a couple of egg crates to hold them in order where they came from

Cover the valve area up while getting new shims

have a little magnet handy

[catamount]

have a little magnet handy

+1

I'm in the process of re-shimming all of the exhaust valves on my '02 Speed Triple. They were all too tight (15k miles).

My regular small magnet-on-a-pole wasn't strong enough to pull the buckets out so I found some beefy magnets at Lowes that pulled 'em out without an issue.

The oil around the buckets keeps quite a bit of tension on them before they release.