Valve clearance tolerance

[adventuredon]

just been checking my valves and found that the feeler guage I had, could measure either .20 or .25. (no more increments available). So when the inlet valves tolerances are loose at .20 and tight at .25 I am left wondering whether it could just about be .24 (tolerance allowed is up to .23) . So my inlet is some where in the middle of .20 and .25. Same on both inlets. Outlets are all good.

Is this a case of buying a micrometre or further guages to check for definite? Thinking about this in another manner. If the max thickness of a shim is up to .23 and shims can only wear down, can I assume a a .23 (or less) would have been put in when the bike was new. How could the gap increase, how likely is it to be .24 ...

 

[DrFarkoff]

is this on a Twin Cam Don? Can't you use a 20 and a 1 ?? to get 0.21 It won;t be "exactly" accurate but better than guessing just make sure they are clean between

Just its 0.15mm Inlet and 0.3 mm Exhaust on a Pre Twin cam

Get a Snap on Blue Point or a Mac tools Set of gauges they are in o.1mm increments

 

[adventuredon]

Hi yes a twincam. Inlet max tolerance is .23 I only have 1 x .05 on the guages available. Hence its either a .2 or .25 etc. Thanks

 

[DaygloDavid]

Recently checked the Valve Clearances on my 2012 TC.
The Inlet valves are 0.13 to 0.23 mm & Outlet valves are 0.30 to 0.40 mm, a tolerance of 0.1 in both cases.
With the Feeler Gauges I have, I can measure, 0.15, 0.20 & 0.25 (0.20 + 0.05 or 0.10 + 0.15).
My thoughts on the Inlets are, obviously if either 0.15 or 0.20 are a loose fit then all is OK, if 0.25 is tight then I'll let it go, 0.02 in 0.23 is less than 10%, near enough for me.
If it was a loose 0.25, I'd put a 0.05mm bigger Shim in & reduce the clearance.
The Exhaust aren't a problem, got 0.30 & 0.40 Gauges, plus 0.05 to make 0.35.
The Shims range from 4.60 to 5.70mm, http://www.realoem.com/bmw/enUS/sho...26-BMW-R_1200_RT_10_0430,0440_&diagId=11_4294, in increments of 0.05mm.
One of the Exhaust valve clearances was a loose 0.40mm, swapped the 5.15mm Shim for a 5.20mm Shim & the clearance was bang in the middle at 0.35mm.

 

[adventuredon]

Hi DayGlo, yes my exhausts are fine and as of today I have just ordered a micrometre so may check them at some point again. But it seems that all is well .... I guess that that small amount won't make such a difference (if it exists).

 

[Greenman14]

Related question: are the shims marked with their size or would I need a micrometer as well as feeler gauges to set valve clearances myself?

 

[adventuredon]

Came across this just now. Quite a simple bit of maths if this will help those that read this later or are curious of doing it themsleves. http://www.r1200gs.info/forum/14-ma...cement-shim-sizes-dohc-valve-adjustments.html

I believe the shims are marked with their size, but you would need good light, clear of all oil to read it. I had some spares from a previous service and couldn't read them, so just tried them but they were too big. So I have ordered a micrometre from toolstation for 13 quid. Probably noth the best there is, but for use twice a year it'll do. I tried to buy it at the local hardware store but the only one they had was £36 ! Would be cheaper to just buy for new shims all round without measuring!
Can anyone confirm that the cam is not flush on the cam following arm? As in the cam seems to be slanted outwards and arm rides up on outer ridge of cam? HTMS. I found I could get my feeler guage in behind the arm but at the edge, it wouldn't go.

 

[Alan R]

Related question: are the shims marked with their size or would I need a micrometer as well as feeler gauges to set valve clearances myself?

Yes they are marked with the size but you will probably need a magnifying glass to read the numbers. If I recall correctly, the service DVDs recommends that they be measured because they can wear out of spec.
Alan R

 

[Alan R]

Can anyone confirm that the cam is not flush on the cam following arm? As in the cam seems to be slanted outwards and arm rides up on outer ridge of cam? HTMS. I found I could get my feeler guage in behind the arm but at the edge, it wouldn't go.

This was my impression too on checking the valves on my twin cam. The cam lobes are not the same profile throughout and the wear surface does not extend evenly across the width of the cam. Seems strange at first when compared with more straightforward set ups.
Alan R

 

[Bendy toy]

The valve clearances close up as the valve seats wear. So never set them less than the smaller clearance number. But anything between the two values is acceptable.

 

[Smug]

To check valve clearances you need wide cranked feelers in .025mm sizes or convert to imperial and use feelers in .001" sizes. Measuring with .05mm (.002") steps is not very accurate.

Take a look at Blue Point/Snap On.

 

[MattW]

The cams are skew ground which leads to odd wear patterns as the shims bed in. This is what leads to the clearance differences across the cam lobe.

 

[adventuredon]

Thanks Mattw

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