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03 Heritage
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491 Posts
As I understand it:
Yellow is lean
Blue is rich
 

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Hellbound Train
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5,595 Posts
A yellow pipe may indicate nothing more that cheap chrome. Pipes will eventually yellow regardless of A/F ratio.
 

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Registered
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208 Posts
Discussion Starter #4
A yellow pipe may indicate nothing more that cheap chrome
'05 FLHTI with a few clicks less than 10,000 miles. The front pipe is turning yellow. Cheap chrome or normal?
 

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GoFast!
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263 Posts
Yellow means the engine was actually started.
Blue means the bike was actually ridden. :brows:
 

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I'm gonna powder his nose
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537 Posts
Martin64 said:
A yellow pipe is indicative of :

A) Lean conditions?

B) Rich conditions?

Actually:
Blue is lean, yellow is rich.

Yellow is a condition of a rich air fuel ratio where the unburned fuel actually burnes in the headpipe. Allot of the time the chrome will actually bubble off of the headpipe. USUALLY the first 6~8 inches of the headpipe are discolored.

A Blue hue is a result of a lean air fuel ratio condition. Usually the first 8~10 inches of the headpipe are discolored and probably the collector area.

Even if the air fuel ratio is correct, some pipes WILL turn yelllow in the first 2~6 inches, this is due to the thickness of tubing used and pipe prep for chrome.

I saw allot of returns in my day. so I set up a test on the dyno one day to help out the warranty guy to prove what the colors really meant.

Hope this helps
 

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Premium Member
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581 Posts
H-D RKC FLHRCI HDI EFI 2001: my "RIGHT" Screamin' Eagle Performance Muffler got yellow, but actually I have had no problem at all with it. My "LEFT" Screamin' Eagle Performance Muffler has NO discoloration, but the muffler itself literally DECAYED, with BIG/HUGE corrosive holes, just 3,5 years after the purchase (check out my thread "NEVER buy Screamin' Eagle Perfomance Mufflers! NEVER!") !
 
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