Topic: 'Go, no go' method of adjusting tappets

[rempy]

Could someone explain the 'go, no-go' method of adjusting tappets? I
searched the archives but all I found was people saying 'use this method!' 

[TwoTired]

Select a gauge known to be "just" too large to fit into the clearance.  This is your no-go gauge.
Select another gauge known to "just" fit in the clearance.  This is your go gauge.

Adjust the clearance gap so that the no-go can't get into the gap, but the Go gauge can.

[IHWillys]

I don't know the specifics of this method but it sounds to me similar to the procedure of checking/setting headspace in a firearm.  One has a gauge called the "go", one called "no go" and also a "field" but that's not relevant here.  Anyway, a go gauge should allow the bolt to close, ie should fit between the rocker and valve.  The no-go should not allow the bolt to close, ie should not fit between the rocker and valve.  What the thicknesses of these two gauges are would depend on the specs.  The go gauge should be atleast the minimum spec, and the no-go should be at the maximum spec.  Thus if the go gauge fits, the gap is at or above minimum, and then if the no go does not fit, the gap is not past the maximum.

I also don't know why this would be the preferred method of setting valve clearances as it would allow for the clearances to range across the entire spec range from valve to valve.  I'd prefer to have a similar tolerance from valve to valve, and may also tend to set intake on the "tight" side but exhaust on the "loose" side, or vice versa, etc.

I am open to learning more...

Ken

*edit* Well, TT put it much more succinctly. 

[rempy]

Select a gauge known to be "just" too large to fit into the clearance.  This is your no-go gauge.
Select another gauge known to "just" fit in the clearance.  This is your go gauge.

Thanks - makes sense. But then how does one find the 'known' variable in that equation? There's a
factory specification, but no deviation tolerances that I can find. Is it a rule of thumb thing, ie if the
spec is .004 then .005 should be tight, but .006 should be a no-go?

[bistromath]

I have feelers in 0.002 and 0.0025. This lets me get my intakes much closer to 0.002 than using an 0.003 feeler as the "no-go".

[Don R]

The feeler should drag when pulled through.

[markb]

I have feelers in 0.002 and 0.0025. This lets me get my intakes much closer to 0.002 than using an 0.003 feeler as the "no-go".

That's what I use on the intakes on my CB750's.  Then I use a .003 as a go and .004 as a no-go on the exhaust.  Might be just slightly looser than spec but better that than too tight IMO.
Mark

[TwoTired]

Select a gauge known to be "just" too large to fit into the clearance.  This is your no-go gauge.
Select another gauge known to "just" fit in the clearance.  This is your go gauge.

Thanks - makes sense. But then how does one find the 'known' variable in that equation? There's a
factory specification, but no deviation tolerances that I can find. Is it a rule of thumb thing, ie if the
spec is .004 then .005 should be tight, but .006 should be a no-go?

If the spec is 0.004, that that is the goal.

A 0.004 should "just" fit in the space with a little drag during the slide in.  If you stack a 0.0005 on top of the feeler, making a 0.0045 total no-go feeler, it should not go in the gap.

Certainly a 0.005 would be a no go, as well as a 0.006, 0.007, and anything larger.

[MRieck]

"Go" / "No Go" generally applies to shim/bucket arrangements

[rempy]

Excellent - got it. Thanks for the help all.