T H E  O L D  G R E E N  B E E M E R
RIDING A 1974 BMW R90/6 FLAT TWIN



TIME FOR NEW VALVES AND GUIDES


The old beemer was becoming a little smoky lately.
At first I thought the engine breather
was playing tricks but this was not the case and after pulling the heads it became very
clear there was work to be done.  I decided to replace the valves and guides.Valve
stem into guide clearance was intergalactic, the valves could wiggle quite a bit in
the guides. So this looked like: New guides, new valves, seat regrind, and to
finish it off new valve springs.  Ordering parts is the easy bit, but receiving
good undamaged parts seems to become a bit of a hassle these days.



I'd made an order here in Holland by a well known BMW parts supplier: 4
AE brand
valves, guides, springs and some small items ... The small items and the springs
turned out to be ok. Three guides ok but one guide bored completely excentric
The
valves turned out to be a bit of a disappointment as well, the stems were
too rough for my liking and damaged ( nicked ). It looked as if they where
hit by a sharp object. By looking at it closely I think I know what kind of
objects :  Heads of other valves is my best guess. Conveyor belt?





IVT valves showing exactly the same sort of damage as the AE valves did




So I returned those items and got a refund. As the AE valves were cheaper than
Até or TRW  brand valves I thought ... well that's that, lets get something better.
This time I ordered the 4 valves and guides via another supplier here in the
country. These valves come from a well known German BMW specialties
supplier, selling these as  ''Top Quality ". Hmm ... , look what I got
today.
Why is it that valve manufacturers seem to have a hard time in making
clean undamaged valves these days, anyone out there who knows?



FRESH OUT OF THE PACK ... DAMAGE INCLUSIVE





These are hard chromed stems





This does not look good to me





Some of the nicks do not rise above the surface of the stem





Others do and make the valve stick into the guide





And can work as a rasp, not a good start for long guide life





Hard chrome is beautiful in preventing boudary friction ... if it is smooth ...
I know all this can be polished away quite easily but it sucks that
these new parts come out of the wrapping like this...





Just for information I've sent the German supplier an E- mail
about this
No response yet ... nothing , zero, not good



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