I got my bike out this morning after it's been setting in the garage for at least a month. I noticed that it doesn't sound like it normally and after inspecting I noticed the back cylinder isn't 'hitting' as hard and the from one.
I put my had behind to check the differ and I noticed the rear one left black on it as well. As luck would have it I was running late for work, so off I went without any issues except the idling when I was stopped.

To make a long story short I pulled the plugs out when I got home and they looked good. I swapped the front and back plugs to test and when I fired it up the rear cylinder is still the same??

It's a 06 FLXH with the factory carb. any ideas???

 

If you have a factory type header pipe system, you will have a different pressure as felt at the exhaust tips. Completely normal, go ride.

 

I notice the same thing on mine. I first became aware of it after an engine build and dyno tune. I first thought something must be a little "off" with the tune and needed to be worked out. But I was shown the exact same condition on several other bikes with similar mods. We were all running true duals with engine mods. The only significant difference between mine and theirs was the choice of cams and exhaust. Mine=SE203's and Bub 7 true duals. Theirs=???cams and Rinehart true duals.

I have experimented with timing and VE tables and can get the exhaust pulses to more closely match. Timing had no effect. Increased VE percentage made a difference. But I found that the rear had to have a much richer AFR to accomplish this. I don't know what the true AFR was since I don't have a wide band to check it against. But it smelled heavily of unburned fuel so I settled on the unbalanced pulses at idle. I don't know what the right answer is either.

BTW, using SEST for tuning if you were wondering.

 

Thanks guys!
I'm running true duals on mine also. I'm just glad it's nothing wrong.

thanks again.