—ยท
Bru1\f\J MOTORRAD Gru1BH
BMW MOTORRAD GMBH โข 8 Munchen 40 โข Postfach 400360
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Buro: Munchen-Freim;inn, YOlckarslr. 9
Fernsprec11er: (089) 32 5025
Drahtwort: Baymolorrad
Telex: 523313
Bankkonlen: .
Deutsche Bank AG. Munchatn, 72/06 600
Bayeriache Hypolh4kenโข und
WechselยทBank, MuncllBn, 318156200 โข
PostscheckยทKonto: 2002 3~ โข 807 Muncher,
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lhre Zolchโขn lhre Nachrlchl vom Unaare Zelch11n Munch en,
6. 1. 75 …. โข—ยทยทยทยท. __R ‘~~-:J_~9s/Nab __-ยท_ยท_ _ 20th February, 197:
Batrelt:
R 90 S – Blue Exhaust PiEes
Dear Sir,
It is not unusual for exhaust pipes especially of our goo cc
models to turn blue. Also, this has nothing to do with the chrome
quality.
We do understand tha~ many customers are reluctant to accept our
argument that the turning blue 1s normal and unavoidable. โข
On modern 4-stroke gasoline engines, theยท exhaust value opens
during the labour sยทtroke and causes still burning mixture to
escape through the exhaust pipe. The escaping burning gasses have
a temperature of approximately 6500 C and cause the exhaust pipe
to glow. Une:xact adjusted ignition and valves could cause even
higher temperatures. The 0 blue-turning 11 could be avoided by using
doub1e”exhaust pipes. This solution would be far too expensive.
Glowing exhaust pipes are nothing unusual. and. harmless …
Our ~otcrcvcles are built with the highest quality 0ยฃ material and
excellent worksmanship to ens~re long life and top safety features.
. .
We can only recommend to use high grade fuels ยทand to have your
motorcycle serviced at regular intervalls at yo~r authorized BMW
dealer. โข
We hope this information will satisfy you and erase any doubts
concerning quality ;,;uld. d.~p~udability.
Yours faithfully,
BMWM OTORRAGDM BH
Milnchen
i.A.
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About the Service Bulletin Archive
Searchable index of BMW service bulletins for repair and parts installation for a variety of 247 models. This is not an exhaustive list. If you have ones to share to help complete the archive, please contact us directly.

