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F800GS - Camshaft bearing cap unit


14TLC

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During a valve check on one noisy F800GS I have noticed these wear patterns on the camshaft bearing cap unit. Feels very smooth on touch and can't feel anything by passing across with fingernail. Camshafts and cylinder head looks and feels OK.

What could cause this? I don't think it is oil supply. Maybe improper tightening during previous valve adjustment?

 

And yes, the valve clearance were loose, above recommended clearance.

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PXL_20211005_161405496.jpg

PXL_20211005_161427222.jpg

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dirtrider
2 hours ago, 14TLC said:

During a valve check on one noisy F800GS I have noticed these wear patterns on the camshaft bearing cap unit. Feels very smooth on touch and can't feel anything by passing across with fingernail. Camshafts and cylinder head looks and feels OK.

What could cause this? I don't think it is oil supply. Maybe improper tightening during previous valve adjustment?

 

And yes, the valve clearance were loose, above recommended clearance.

 

Morning 14TLC

 

Good question, I have seen other 800 engine cam carriers look like that (even worse). I have seen a lot worse looking. 

 

I'm not sure if it is an original machining issue (part heats as the cutting bar advances growing the alloy then returning to a slightly smaller diameter after re-cooling).

 

Or possibly the oil runs off that cam area after longer parking periods (there are scallops in the cyl head in the cam bearing area so that part or  the cam bearing doesn't retain oil)

 

If you are worried you might try to plasti-gauge those cam bearings (do one side at a time & try to remove as much valve load on the cam as possible on the side being measured. 

 

Also possibly (precision) mic the cam bearings journals across the width of the bearing to see it slightly  tapered.  

 

Or just do a couple of Kawasaki KLR's, you will then think what you have is a precision fit & look. 

 

Here is a 14k  cam carrier__ 

 

 

 

 

BMW 800 cam carrier 14K miles.2.jpg

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1 hour ago, dirtrider said:

Or just do a couple of Kawasaki KLR's, you will then think what you have is a precision fit & look. 

 :classic_biggrin:  That is a good one

 

I have seen many like the one on your picture and also like the one I have now. I have never measured them since I think it is not that bad. But what got me thinking this time, and maybe this time I paid more attention and noticed,  is the groove part for the inlet camshaft which is different from the one for the exhaust camshaft. Now I see that it is the same like the one on your photo. I suppose is the original machining issue, if it is an issue at all.

 

I think that tightening procedure and sequence may be in play here. I think that the carrier flexes while tightening and maybe it should be done in sequences till the end torque of 10Nm. I remember, years ago when I did the first valve adjustment on F800 that there is significant pressure on the bearing cap unit, especially on the cam chain side. On F650 twins with less aggressive cam lobe profile is not that noticeable, but on F800 I can see how the bearing cap unit flexes. For that purpose I made tools like the one for the K1600. I have one set for the K1600 and I am using the nut part with the bearing and made the stud bolt part specific for the F800.

 

 

PXL_20211005_161405496.jpg

PXL_20211005_161427222.jpg

k1600.jpg

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