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Old 01-09-2013, 04:24 AM   #15
roger 04 rt
Beastly Adventurer
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Joined: Nov 2011
Location: Massachusetts
Oddometer: 2,272
Originally Posted by carlesonra View Post
While checking valves on my 2009 1200GS at 40,000 miles, I noticed spark plugs showing a lean mixture. I have a K&N installed but no other change and realize manufacturers have clean running as a priority. Question is: are other riders showing light spark plug coloring which is kinda normal or Is this something that needs attention and if so what? I have not noticed any spark knock when pulling at lower rpm.
Thanks for your time in responding.
Bob Carleson
Arroyo Grande, CA
R1200GS, R80RT, DR650
Light spark coloring is normal in engines with O2 sensors. As has been said many times. Through this thread.

Interestingly, I have used a Wideband O2 sensor to add 6-8% to my fueling and the plugs still are light. (Below) how do your plugs compare to mine?

The mixture set by the narrowband O2 produces the highest exhaust gas temperature. Go richer and the EGT drops and surprisingly to some (but not pilots of piston engines) the EGT gets cooler as you go leaner.

Here is an Autolite Plug with 2,000 miles of mostly local driving at 13.8 which means 6% richer.
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