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Offline awjdthumper

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Re: Measuring Valve Clearance (Tips)
« Reply #10 on: March 11, 2020, 02:02:16 PM »
At the moment, using imperial gauges might actually be the best approach; namely:

13 thou giving 0.3302 mm
15 thou giving 0.381 mm

I think the lower limit is the critical one since this could lead to a burnt out valve if not met. It's likely that the worst that will happen if you exceed the upper limit is a slight loss in performance or a slight increase in emission levels.

Unless someone comes up with a better approach, I might well go for the imperial feeler gauge route :084:
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Online Rtwo

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Re: Measuring Valve Clearance (Tips)
« Reply #11 on: March 11, 2020, 02:36:19 PM »
I use 3 gauges (Min, Mid & Max)
Easy enough then to bring it back into spec with either swapping them around and/or a replacement or two

Taken from a Draper set, my Tiger gauges
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Offline awjdthumper

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Re: Measuring Valve Clearance (Tips)
« Reply #12 on: March 11, 2020, 05:16:55 PM »
I assume for the exhaust clearances, most people are likely to also need the 0.305 mm (12 thou) gauge as well if they are out of spec; that is, if a clearance is less than 0.330 (13 thou)?
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Online tigerman1960

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Re: Measuring Valve Clearance (Tips)
« Reply #13 on: March 11, 2020, 07:25:15 PM »
with the greatest respect, your thinking about this wrong, if you put a 0.38 in the exhaust gap and it will not go in, you then try  the next one down, if that is a 0.35 and it fits, that gap is within the range specified, why do you need to know the exact measurement ? its in tolerance, move on to the next one.

if you put a 0.30 in and its tight, you know that it is out of tolerance, so you are going to have to change that shim, which means taking out the cams, and a lot of work,then you measure the shim that was in there, and buy a thinner one to make the gap larger.

you dont need to know the exact feeler gauge measurements, because any that are out of tolerance will be sorted with a micrometer.sorry if i am speaking out of turn, i hope this comes over ok.
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Offline awjdthumper

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Re: Measuring Valve Clearance (Tips)
« Reply #14 on: March 12, 2020, 07:00:04 AM »
*Originally Posted by tigerman1960 [+]
with the greatest respect, your thinking about this wrong, if you put a 0.38 in the exhaust gap and it will not go in, you then try  the next one down, if that is a 0.35 and it fits, that gap is within the range specified, why do you need to know the exact measurement ? its in tolerance, move on to the next one.

if you put a 0.30 in and its tight, you know that it is out of tolerance, so you are going to have to change that shim, which means taking out the cams, and a lot of work,then you measure the shim that was in there, and buy a thinner one to make the gap larger.

you dont need to know the exact feeler gauge measurements, because any that are out of tolerance will be sorted with a micrometer.sorry if i am speaking out of turn, i hope this comes over ok.
I think you may have mis-interpreted what I was trying to say.

Strictly speaking, you only need two feeler gauges to determine whether an exhaust clearances is in spec; 0.330 mm (13 thou) and 0.381 mm (15 thou), assuming you are using a set of imperial feeler gauges. If the 13 thou is a GO and the 15 thou is a NOGO then you are in spec!

The problem is if you find you are out of spec which will mean that, assuming the exhaust clearances close up over time, you find that the 13 thou gauge is also NOGO. In this case you will then need to use smaller feeler gauges until you find one of them is a GO.

If you find the largest gauge that is a GO is M thou for a particular out of spec exhaust valve then its shim will need to be reduced in thickness by at least (13-M) thou. For example, if the clearance is actually 0.310 mm, and therefore out of spec, then the largest gauge that will be a Go will be 12 thou (0.305). Reducing the shim thickness by (13-12) or 1 thou will increase the valve clearances to 0.335 mm which will then be in spec.

However, it looks as though shims may only be available in 0.05 mm or 2 thou steps. Therefore, if a clearance is found to be out of spec, its shim thickness will need to be reduced by 2 thou if M is equal to 11 or 12. In the example above, if the shim thickness is reduced by 2 thou, its clearance will end up being 0.36 mm which again makes it in spec.

For me, the challenge will be if a particular clearance is found to be in spec but between 13-14 thou; in other words in the bottom half of the tolerance range. Assuming I'm going to have to take the camshafts off and adjust some other out of spec shims, I might as well consider changing any in spec clearances in the 13-14 thou range to put them in the 14-15 thou range - doing this will mean it will then take them longer to eventually go out of spec assuming the exhaust clearances close up with time.

In this case, I ideally need to reduce the shim thickness by only 1 thou but I'm not sure this will be achievable given the limited size range of shims available. In this past, I've used the technique of lapping shims on fine emery paper to reduce their thickness but this is not something I would try on my Triumph. The alternative might be to measure the thickness of the shims I have available and to see if the tolerances on them gives me the actual thickness I need. However, I won't really know if this will work until I try doing the valve clearances.

So, in conclusion, you only need two feeler gauges to determine whether an exhaust valve clearance is in spec but addition feeler gauges to determine the new shim thickness if a clearance is out of spec!
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Offline cat10

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Re: Measuring Valve Clearance (Tips)
« Reply #15 on: March 12, 2020, 07:09:14 AM »
Well Said !

Online Paulhere

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Re: Measuring Valve Clearance (Tips)
« Reply #16 on: March 12, 2020, 08:27:08 AM »
*Originally Posted by awjdthumper [+]
... you only need two feeler gauges to determine whether an exhaust valve clearance is in spec but addition feeler gauges to determine the new shim thickness if a clearance is out of spec!

That's it.

I use mid as my min 'cos any below that I will change for mid or above. Each to their own on that.
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Online philmcglass

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Re: Measuring Valve Clearance (Tips)
« Reply #17 on: March 12, 2020, 12:54:58 PM »
I started to write a long post about this. Doing calculations and everything.

This site has a listing of available shims from Triumph .025mm (1 thou) steps.
https://www.worldoftriumph.com/partscatalog/catalog/listing/catalog/triumphmc/modelid/560048/block/100076321-1-2/

Site here to calculate changes to out of spec clearances.
http://www.agbuzz.com.au/valve/valve_intro.htm

I got feeler gauges (dual marked metric and imperial) ranging from 0.127mm (5 thou) to 0.762mm (30thou) in steps of 1 thou

Question is: If shims are 0.025 mm apart,  do we need feeler gauges with step of half that i.e. 0.0125mm (half a thou) steps to ensure the correct shim is selected?
Maybe thinking too much about it.

(TMTOMH)
« Last Edit: March 12, 2020, 12:56:39 PM by philmcglass »
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Online Rtwo

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Re: Measuring Valve Clearance (Tips)
« Reply #18 on: March 12, 2020, 04:18:45 PM »
Lots of other bikes have 9.5 mm shims, you don't need to get Triumph ones

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Online CB250G5

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Re: Measuring Valve Clearance (Tips)
« Reply #19 on: March 12, 2020, 06:28:34 PM »
*Originally Posted by Rtwo [+]
Lots of other bikes have 9.5 mm shims, you don't need to get Triumph ones

Mine were 7.48mm   Same as many Jap bikes
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