Valves Set @ (I0.006) (E0.010)

[Air4Life]

I have just put 25 miles on since I went with the above clearances and I too find the extra tapping to be a bit disconcerting.  :-/  It starts, runs, and shuts down fine.  I still may tighten it up a bit.

Next will be to adjust the fuel mix on the right side.  Its running a bit RICH.

Wishing you all, a good to great New Year.

Ange

[Bob_Roller]

Another source of valve noise, is clearance between the rocker arm and the two blocks on each side of it .

If you have an excessive amount, there are two methods to reduce it .

First is to loosen the nuts that hold the rocker arms, then use a clamp or large adjustable pliers to get the blocks to turn a bit and take up the clearance .

The other method is to measure the clearance (cold) and get shims from BMW to take up the gap .

[Air4Life]

Thanks Bob.  I will store that information for when I go back in.  

Today the weather was supremely good here in NJ @ 53 degrees.  Tuesday, reality starts off with our first dip below freezing at an expected 29 degrees F.  Glad I got to ride today.  

I started the thread so as to note the difference between the old book version of valve clearance setting with the new.  My interpretation of the added noise would appear to be directly related to the extra gap  added.  Not to say the blocks aren't adding to the music.  I don't recall there being to much play in them though; but I will definitely double check when I get back in there.

Enjoy the ride, Ange

[montmil]

Suggest you try 0.008" on the exhaust. Much of the excess BMW music will disappear.

Monte

[Barry]

It starts, runs, and shuts down fine.

Just curious did you notice any difference at all in the running.  The wider clearances would very slightly soften the valve timing. Probably imperceptibly improving low rev running. Might also in marginal conditions make the engine ping due to increasing the effective compression ratio at low revs.

[nhmaf]

The clearance from between the pillar block and the end of the rocker is basically specified to be the thickness of oil film, or 'nil'.   I've basically found this to be about .001 inches to .0015 inches.   In my experience, as long as this is no more than .003 inches you should be fine and added noise is minimal.   But, anything over .003 inches goes indeed make an increase in valve train clatter.  You definitely do not want the blocks to be pressing hard onto the rockers (truly "0" clearance) or there will be excessive wear.

[Barry]

You definitely do not want the blocks to be pressing hard onto the rockers (truly "0" clearance) or there will be excessive wear.

Agreed.

I think I had mine too tight at one point. Although there is no way to simulate full travel it's a good idea to back off the tappet adjuster and swing the rocker through the widest arc possible to check for binding.

[badbmwbrad]

"A tappy valve is a happy valve."

My understanding is the 1982 boxer engines had stainless steel exhaust valve seats which was intended to be good material for mitigating valve seat recession.  Stainless steel is less well-suited for heat transfer.  

Heat from the hot exhaust valve's disc must be conducted into the valve seat and cylinder head cooling fins during the short period of time the exhaust valve is closed.  If the exhaust valve disc heat is not transferred into the st. stl. valve seat then the disc overheats then deformation occurs.  The deformation is manifest as rapid loss of valve stem/tappet clearance and a disc which appears shaped like a tulip.    

Setting the exhaust valve clearance wider results in increased disc/seat contact time; providing more time for disc heat transfer into the seat.  My opinion is the wider clearance would slow the loss of valve stem/tappet clearance.    

[Barry]

Good point and perhaps one reason why BMW increased the Exhaust valve clearance from .006" to .008" at the time when those seats were introduced with the new 81 model and then went on to recommended .008" for all airheads in March 82.

Impossible to be precise without knowing the cam profile but it would be interesting to calculate how much longer the valve stays on the seat. The exhaust valves are open for nominally 232 Degrees in each 4 stroke cycle or 2 revolutions therefore they are closed for 720 - 232 = 498 Degrees.

How many extra degrees would .002" make ?

I know this isn't our cam but the timing is quite similar and it's the best thing I can find to make an estimate with. In the attached cam chart .044" makes 46 Degrees difference in valve timing so on average roughly 1 degree per thou.  The cam profile is not linear between .006 lift and .050" lift so .002" difference at the beginning of the lift could be several or even many times the average lets say 3 degrees per thou although it could be a lot more. That would be an extra 6 degrees on 498. Not a lot then percentage wise. Anybody have any better insights on this.

  

[tvrla]

Thanks for doing those calculations Barry! I'm impressed! I never would have thought of a way to figure that one out!

You're right, a few thousandths really makes very little difference. But maybe in really hot weather when pushing it, a little wider clearance could have a positive effect. Or perhaps, just taking frequent breaks to cool down and not pushing it hard is the better answer! Eh?

Frankly, I'm not excited about the effect wider clearance has on rockers from the constant pounding.

[Air4Life]

I found the rockers to be within tolerances.  I readjusted the exhaust to .008 for compromise sake.  I'd be curious to compare my setting to others; I imagine there's a disparity between me and you.  

I am beginning to believe that my first recognition of the valve noise as being 'disconcerting' was on the exaggerated side.  Anyway, I'm happy where it sits now, and will leave it be.  

I just came back from a local ride to warm it up; conversely to cool me down.  Forty degree temps are the perfect governor of speed. Over 45 MPH and the governor kicks in.   8-)

Thanks all for your input.  May this be a better year for us all. ange

[tvrla]

I generally set my valves at four and eight. When setting, push down on the adjuster to break the oil film between there and the lifter - that can make a difference of a thousandth or two. Every little bit helps.

They shouldn't be knocking, just lightly ticking.

[Air4Life]

Good advice.

I think my original concern was borne more out of the mind working over actuality.  It really doesn't sound any different now.

And yes, they tick and tick, very consistently.  

[Air4Life]

R65 +1

[Barry]

Ange

Did you stick with the .006" and .010" clearances ?

I did mine to those specs shortly after you started this thread and I got to say I like the way the bike runs on these settings. I've noticed no significant increase in noise and I wear an open face helmet so I'd notice if there was. I made sure they were a tight setting by pushing firmly on the adjuster side of the rocker to displace the oil film. They are probably closer to 5.5 and 9.5 thou.  

What I did notice was an increase in idle revs together with improved cold running and low rev tractability. I was even able to turn the mixture screws in a fraction. All that fits with the more efficient running at low revs produced by slightly softer valve timing with less overlap. I was surprised by the extent to which 2 thou made a difference.

As wirespokes pointed out a question of concern arises - are these settings still comfortably on the quieting ramps ?  I think they are. One clue is that BMW quotes it's cam timing at 80 thou lift which is way above the more normal 50 thou used by most everybody else. Why would they do that ? Maybe it's because the quietening ramps are longer than typical. No way of knowing for sure without a cam chart. It's a reassurance that Snowbum is happy to recommend  these settings and I guess he will have been aware of this issue.

For anyone interested in the effects of varying valve clearances I found these quotes when researching the topic.

"Decreased valve clearance lengthens valve overlap allowing fresh charge dilution by the exhaust gases at lower engine speeds therefore reduced valve clearances require a richer mixture and larger clearances a weaker mixture."

"Tappet clearance greatly affects idle mixture, a wide tappet clearance makes the idle mixture appear to go rich"

"Playing with tappet clearances (within reason) can show which way you need to go with idle mixture, if it runs better with wider clearances then you need to go richer, and visa versa."