Valve Shims & Clearances (DOHC)

Well, today I decided to check all the valve clearances on my 63k miles, 2011 DOHC bike. It's done a fair few miles, so I was expecting to need to get new shims in the near future.

The bike runs very nicely with no top end tapping.

I also did a compression test which gave me readings of 13.5 Bar for the left cylinder and 14.0 Bar for the right cylinder - which seems to indicate excellent compression. This was with a cold engine though, so I'll do another one in the future with a warm engine, but I wouldn't expect a whole lot of difference. In any case - it appears the rings and valve seating is good and there's no need to look further at those for now.

Valve clearances came out as follows:



And the valve gear all looks nice and clean as well:




All looks good and the clearances are all inside tolerances. However - it's getting close to the tolerances, in particular for the Right cylinder exhaust valves and the top intake valves on both cylinders. I need to plan to replace the shims here to bring it all back towards minimum tolerances.

So some questions for those who know what they are talking about!

1) Would you replace the shims on ALL the shims at this point, or just the ones that are close to maximum tolerances? Half of them are right at the midpoint between min and max tolerances.

2) If replace ALL is the way to go, would you then shoot to get everything as close to the minimum tolerance as possible? Or aim for midpoint? Or somewhere else?

As to the procedure for changing shims, I have read up on it in my Haynes manual, read some threads here and will watch some youtube videos later. But - is my understanding of the procedure correct?

1) Cold engine at compression TDC for the relevant cylinder
2) Measure and record current valve clearances and compare to factory spec.
3) Working one valve at a time, remove e-clip, remove cam follower, remove shim and measure shim with micrometer
4) Do some maths.
For example - Exhaust Valve A. Factory Spec is 0.30 to 0.40 mm. Measured clearance was 0.38mm (0.8 away from factory minimum).
Factory fitted shim says 5.0mm, but measures 4.6mm due to wear. To reduce clearance down to 0.30mm, I need an additional 0.08mm shim thickness. Therefore the correct replacement shim will be 4.6mm plus 0.08mm = 4.68mm. However that shim doesn't exist, so I need to round down to 4.65mm to avoid making the clearance too small.

Fitting a 4.65mm shim in this case should reduce clearance to 0.33mm

5) Fit correct shim, replace cam follower using new e-clip.

So is that basically the right way to do this? I think what will be tricky here is not to mess up the different valve followers and shims between the measurements and receiving new shims (unless Vines BMW keeps all in stock at all times and I can just nip over there and pick them up). However a piece of cardboard with proper markings and holes to keep everything organised should work.

Also, does anyone have any tips from experience of doing this to make the job simpler? It seems easy enough as long as I am organised and methodical....

Sorry for the long post, but I want to get this done properly!

If bike runs well and all in spec then leave for next time.

One question I would ask is how you measured them so accurately. I am just an amateur at this stuff so I find it hard to be that specific. For example, if a 0.2 feeler gauge will go in - just, at a squeeze - then how do you know if clearance is 0.18, 0.17 etc...?

Never done one of these, but have done a few Triumphs in the past. I wouldn't change anything right now and would measure them all again in a few thousand miles. In my experience valve clearances tend to close up due to valve seat wear rather than open due to cam/rocker wear unless something is wrong, so being at the top end of clearance is maybe better than too tight.

I'd check them again later and find out which way they're moving, if at all, before you go to the effort of changing them potentially in the wrong direction.

Others with more experience of BMWs will no doubt tell me I'm wrong!

NicD said:

If bike runs well and all in spec then leave for next time.

One question I would ask is how you measured them so accurately. I am just an amateur at this stuff so I find it hard to be that specific. For example, if a 0.2 feeler gauge will go in - just, at a squeeze - then how do you know if clearance is 0.18, 0.17 etc...?

Click to expand...

Good question.....and the answer is using a set of dual marked, but basically imperial feeler gauges. For example, for the intakes, I have 5, 6,7, 8 and 9 thousands of an inch - which are also marked .127, .152, .178, .203 and .229mm. I'm just rounding these off to .13, .15, .18, ,20 and .23.

Couple this with a pure mm set of gauges and you can get pretty close!

Stu23 said:

Never done one of these, but have done a few Triumphs in the past. I wouldn't change anything right now and would measure them all again in a few thousand miles. In my experience valve clearances tend to close up due to valve seat wear rather than open due to cam/rocker wear unless something is wrong, so being at the top end of clearance is maybe better than too tight.

I'd check them again later and find out which way they're moving, if at all, before you go to the effort of changing them potentially in the wrong direction.

Others with more experience of BMWs will no doubt tell me I'm wrong!

Click to expand...

Good point - and they are all in spec anyway, so there's no urgency in doing them. At least I know where they are at now and can plot any trends....

My 2012 TC valve clearances have not altered 1 thou in 55k miles.
In my experience, generally with OHC motors, the clearances decrease.
Valve seat recession rather than cam wear. But someone with more experience with these engines may be able to help more.

Similar here. 86,000 miles and valve clearances have never really changed. All are towards the looser end of the range. I never give it a second thought except at service time.

Well, this is encouraging news! Looks like a job I don't need to plan do after all. I'll just monitor every few thousand miles and see if anything changes.

My experience is that the valve clearances on the TC engines close up rather than become larger.
I changed a few of mine at about 40k as a couple were getting to the minimal end of tolerance. It's very easy to change them, and you can often swap positions around to avoid buying lots of new shims. I'm happy to share the detailed records that I kept for my last TC... But they're handwritten in my "big black book of motorcycle maintenance"... I never quite mastered spreadsheets!

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As has been mentioned they don't change much, they do close up with valve wear if they do change,
I would leave them nearer max, minimum leaves no tolerance,
I have ended up with the tc engine again as now on a R9 t,
checked and noted clearances at 600 service, not expecting a big change,

Interesting. Thanks lads.

It seems like the general consensus is that the clearances close up. In which case I seem to be in a good place.

It surprises me as I would have though that cam or shim wear was faster than the valve seats, but hey ho. It is what it is.

So with the measurements being all in spec, plus the good compression test results I now feel happy about the condition of the top end of this engine. Replacement secondary coils are arriving tomorrow and I will button it all up and get out on the road again.

a well designed, well made set up should only get them closing up due to wear of the valve seats (which is why you check them) however I was going to say..... just coz a given shim has a replacement size, that might not get you like for like clearance due to wear and tear of the parts in place,

there's was bit about these doing mega miles in MCN recently (190K?), only engine fault was a burnt out and or snapped valve. bloke drove it home and swapped it out and "got away with it" allegedly...

sounds pretty easy to get at the shims.... if it pops out and you can swap in a few seconds you could play to level them up. on engine's where its pull the cams out and disturb everything then often they'll all move quite a bit as it gets disturbed and not much fun....

I would rejoice at finding the clearances so good and look again in another 20K miles or so. They seem to be very stable. A very easy engine on which to measure and if needed adjust the clearances.

Important to turn the C-clips so they are open-side facing into centre of engine, so there is no chance to dislodge them when replacing the rocker cover - I think it is mentioned in REPROM..

My bike was one where the cam timing was not set correctly in the factory, it had to be corrected using a special tool which was a jig with 2 square holes which held the cams in alignment while you tightened the sprocket securing screws. You can check the timing using a straight edge, highly unlikely to be out but if you are in there, it is an easy one to do.

I actually did check the alignment of the timing marks with a straight edge yesterday! They line up perfectly.

Haynes manual also mentions correct positioning of the clips, but as I am not going to be replacing any shims now I don't need to worry about it.

And you are correct - this is a super easy engine to work on. It took me about 30 minutes to measure all the clearances - even doing it twice just to be sure.