Late last year I had adjusted the valves on my 82 R65LS (.005" intake, .010" exhaust) and the bike had
been running well, though at the time I did notice the tap-tap-tapping noise of the little sewing machine
was a bit louder than I recalled being 'normal'. I think that I like running the intake and especially the
exhaust valve clearances on this stock-valve-seat bike a little bit on the generous side (factory specs are .004"/.008") to try to
improve valve heat transfer and hopefully avoid having to do the valve&seat replacement thing for a few more years yet.
Anyhow, this spring the bike continued to run fine, but I decided that the tap-tap-tapping was louder than it
ought to be and it was getting on my nerves, especially the right hand cylinder, so I decided to check the
adjustments and see what could be the cause of the noise.
Valve clearances were spot on still, but I noticed that the right hand cylinder's rocker had about .003" to .004" of
end play (vertical movement between the mounting blocks, while the intake rocker had essentially "0", or
at least less than .001", the limit of what I could measure. I checked the left hand cylinder, and in that case, it was
the intake rocker that had the .003" of end play and the exhaust rocker had none. I found it interesting that the
right cylinder seemed so much louder than the left, when the clearances were the same from side to side, and one rocker
on each side was "loose" as far as vertical/end play was concerned. Perhaps the fact that on the right side it was the exhaust
rocker and not the intake that caused the tapping to seem louder when combined with the wider valve clearance.
I checked and retorqued the head bolt nuts to 25 ft-lbs, and they were all very consistent and on the money. I had read several threads about using
a C-clamp, or channel-lock pliers to "adjust" out this rocker end play, and then came across a slightly different method, which I tried out yesterday..
Working on the (2) rockers with end play, I loosened the nut on the lower rocker arm block about 1/2 - 2/3 turn, just to get some of the tension off it. I placed a socket that would go around the end of the rocker arm shaft without touching it up against the underside of the block
and gave it a few "taps" upward with the small end of my war-mace (also known as the BMW exhaust nut spanner tool). I re-tightened
the nut on the block to spec and did similar process on the upper rocker mounting block nut, but tapping down from the top, of course.
I retorqued the nuts, and rechecked the torque on the other head bolt nuts as well - all seemed OK. I rechecked the rocker arm/valve clearances
and noticed that the left intake and right exhaust (which were the (2) that I performed this procedure on) had tightened up by about .003" or perhaps
slightly more. I readjusted the valve clearances on both sides and turned the engine round a few more times for good measure and rechecked.
Valve clearances still good, and no significant vertical movement/end play on the rocker arms ! Yes !
I put the covers and plugs back on, etc. and started her up.
Ah, that is more like what an airhead is supposed to sound like: valves going tick-tick-tick-tick instead of TAP-TAP-TAP-TAP !
So, I guess that I wanted to say that if you are getting fairly loud-sounding valve noises (for an airhead, anyway), to check for rocker arm
end play as a possible cause. The fact that adjusting it out seemed to reduce the valve clearance makes me wonder if there might be wear
occurring in the bushing that I may have to contend with later (out of round ?), but for the moment, I have my fingers crossed.
Has anyone else had similar experience ? While I have adjusted the valves on this and other airheads before, this is the first time that I gave
much attention to the rocker end-play..
Topic: Rocker end-play:Somewhat quieter valves (Read 2531 times)