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Discussion Starter · #1 ·
Hey guys, I have a 06 M109r and while I was changing the exhaust the other day I looked into the exhaust collectors on the jugs. The rear jug was all black from the carbon but the front jug was clean! It was like someone had just slapped in a new cylinder that had never been run on the bike. Like eat off it clean! I have never had any problems with the bike. Always ran smooth and lots of power so what gives? I haven't checked the spark plug color. There is no discoloration externally that might indicate the front cylinder was lean. Any of you guys run into this? Thoughts?
 

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My rear runs a little richer than the front too. I never noticed it with my 2-1, but when I went to the 2-2 pipes it showed up. The upper rear pipe gets more discoloration on the outlet than the lower front pipe does.

I have an FI2000R and run it a little on the rich side, so I expect to see some carbon in the pipes. I just didn't notice there was a diffference front to rear until I went with the separate pipes. And they have a crossover, so if they were true 2-2 it would show up more.

That's why a good dyno tune creates a separate map for both cylinders, as they never need the exact same amount of fuel under the same load.
 

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I may be way off on MY theory, but on car engines there are a small number of cylinders that work more than others and are the usual culprits in a failure. It COULD be that the #1 cylinder (front) is working harder and burning the fuel more efficiently on acceleration and the #2 cylinder works more on deceleration thus more incomplete combustion. If it runs fine I wouldn't worry about it.
 

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Discussion Starter · #4 ·
I'm putting the PCV with the auto tune on my bike later this year so maybe i will see a difference. Thx guys.
 

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When I removed the stock pipes to install the Cobra Tri-Pro, the head pipes were ghost white, both front and rear. That was running stock tuning and Edelbrock air cleaners.

Not sure what the Cobras are like, but since I have it tuned and running somewhat rich, I am sure they are brown now. Not taking them off to find out either.
 

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Hey guys, I have a 06 M109r and while I was changing the exhaust the other day I looked into the exhaust collectors on the jugs. The rear jug was all black from the carbon but the front jug was clean! It was like someone had just slapped in a new cylinder that had never been run on the bike. Like eat off it clean! I have never had any problems with the bike. Always ran smooth and lots of power so what gives? I haven't checked the spark plug color. There is no discoloration externally that might indicate the front cylinder was lean. Any of you guys run into this? Thoughts?
..........It COULD be that the #1 cylinder (front) is working harder and burning the fuel more efficiently on acceleration and the #2 cylinder works more on deceleration thus more incomplete combustion.
I would like to add my theory to this. The front cylinder may be running at an optimal combustion temperature and the rear cylinder may be igniting a bit hotter due to it's physical location. To prevent the rear cylinder from running lean, the ECM instructs the injectors to run a bit richer to cool the combustion temperature and prevent pre-ignition.

Just my two cents.
 

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I would like to add my theory to this. The front cylinder may be running at an optimal combustion temperature and the rear cylinder may be igniting a bit hotter due to it's physical location. To prevent the rear cylinder from running lean, the ECM instructs the injectors to run a bit richer to cool the combustion temperature and prevent pre-ignition.

Just my two cents.
Not likely, this is a liquid-cooled engine. Harley, yes. M109R, NO.
 

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:agree: My bike ran lean even with the Cobra f2000r, once I switched to the Dobek unit it ran like a totally different bike, and when changing out the pipes both cylinders looked the same with a slightly rich coloring, plugs read perfect so leaving it where its at......
 

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Not likely, this is a liquid-cooled engine. Harley, yes. M109R, NO.
Even though it's liquid cooled, the rear cylinder combustion temperature can still be hotter. It could be programmed to run richer in the rear cylinder from the factory by a matter of milliseconds.

Again, this just a theory.
 

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Not likely, this is a liquid-cooled engine. Harley, yes. M109R, NO.
The rear cylinders run hotter on ALL V-twins water cooled or not unless they are offset...air flow still plays a part albeit smaller on liquid cooled then air cooled...and the two cylinders will never get the same amount of air...but you can tune them to get the same amount of fuel/air mix which will help bring them to an even closer internal temperature. I run my fueler on the rich side and both exhausts accumulate some black exhaust build up.
 

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Maybe you just need to get out there and goose it! :bigthumbsup:
 

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The rear cylinders run hotter on ALL V-twins water cooled or not unless they are offset...air flow still plays a part albeit smaller on liquid cooled then air cooled...and the two cylinders will never get the same amount of air...but you can tune them to get the same amount of fuel/air mix which will help bring them to an even closer internal temperature. I run my fueler on the rich side and both exhausts accumulate some black exhaust build up.
:agree::agree::agree::agree:
 
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