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Old 10-28-2012, 07:27 AM   #16
vtbob
wanderer
 
Joined: Jun 2009
Location: Western Vermont
Oddometer: 500
Quote:
Originally Posted by JRWooden View Post
It was mentioned in another thread that typically the valve lash on these engines gets tighter as time/miles go by,
and not looser like most other engines.

.
take a look at the cam/shim/bucket design. there are two modes of wearing in on these engines. one is the cam/ follower wear. as this happen the cam to follower gap will increase...ie get looser. this is the primary wear and it is a sliding interface. when this happen, the gap is measured and thicker shims are added.

there is a secondary factor, that is the valve seat wear and valve deformation wear. these would make the valve lash get tighter. In modern engine with very hard/ high quality valve and seat materials I do not beleive this is the primary wear mode. If some one has better info please pass this on.

the issue of paying for the valve lash inspections for warrantee concerns is valid. If you consider this important pay the couple of hundred for the inspection....consider it insurance to keep insurance/warrantee....

I would like to hear from people on this list who know for a fact that when the 12, 24, 36k mile inspections happens, how many actually have enough wear to cause thicker shims to be added.

I believe most of this inspections ..will only be that...just opening the engine to see that nothing is needed.
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Old 10-28-2012, 09:39 AM   #17
JRWooden
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Joined: Jul 2008
Location: The great state of confusion
Oddometer: 4,112
Quote:
Originally Posted by vtbob View Post
I believe most of this inspections ..will only be that...just opening the engine to see that nothing is needed.
I hear ya bob ... the idea that clearances would decrease with miles is a new one to me....
This is one of the threads I was following on it, there is another one someplace...
http://www.advrider.com/forums/showt...1#post19917471

I am prep-ing to do the check on mine in a few weeks - I do have a baseline for comparison so will post my results.

JRWooden screwed with this post 11-30-2013 at 06:51 AM
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Old 11-29-2013, 06:16 PM   #18
UnDealership
BMW Master tech
 
Joined: Nov 2013
Location: San Mateo, Redwood City
Oddometer: 2
valve lash gets tighter

In my years of working on motorcycles (6 years of working on just BMW and Triumphs)....the v-lash gets tighter over time. Its the area where the valve meets the seat that gets worn. This causes the valve spring to pull the valve further toward the cam system (what ever kind your bike has). Problem this causes is, the valve touching the seat actually cools the valve.

You have probably heard of a "Burnt valve" before. This is when the valve lash gets too tight. The valve does not get its proper cooling and it (the valve) starts to erode. Once this starts its over! You'll need to have the head removed and a new valve(s) installed.

Clicking valves are good! Quiet valves are NOT good! Noisy valves can be a sign some something really weird happening...and you should get it looked at asap.

I hope this can clear up some info on proper valve lash.

Sean
BMW Master Tech
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Old 11-30-2013, 06:57 AM   #19
JRWooden
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Joined: Jul 2008
Location: The great state of confusion
Oddometer: 4,112
Thanks Sean!

I guess I'll just have to get used to that ...

On most of my other bikes (mostly air-cooled Honda dirt bikes) the lash gets bigger with use.

I had intended to do the second lash check myself, but ended up getting it done at a very nominal charge as my water pump was getting replaced under extended warranty and they had to replace the drive gear on the end of the camshaft as the pump had been re-designed ...

Thinking quickly I said ... "Hey ... while you're in there ..."
One valve was a few thousands tighter than desired (not below the low end, but moving that way) so the technician re-shimmed to to be close to the loose end of the range. This was the same thing that was done on the first lash check (but different valve).
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