Guys and Gals,
What would be some common causes for the rear cylinder to backfire during up-shifting?

 

well what have you changed from stock on your bike as far as pipes. breather, power commander ?

and I wouldn't say it's back fire on upshift more back fire when rolling off throttle

 

Exhaust leak.

 

You're right, it is more of a back fire on throttle roll off. Changes include Big Sucker A/C, Fullsac header, Rinehart 4" mufflers, TTS module.

 

My streetglide does same close to same set up except different a/c and running power vision

 

Sounds like you might have an exhaust leak at the headpipe. Slip a 13 mm socket on a 4" extension and see if maybe you can't tighten it up a bit. There are two nuts on each headpipe. They have a compression gasket in there so don't stand on it, just snug it up till it quits popping. You also might have a loose muffler clamp on one of your mufflers.

 

I've always heard try the easy fixes first and that sounds like an easy one.

 

Had the same problem with my TTS tune. What I did was go into the Map you are running and back off the Deceleration and Acceleration enrichment a little. Took care of the problem.

 

What TTS cal are you running? I, too would play with decel enleamnment.. AE adjustments won't do much to help.

What RPM does this do this? Wind it up over 4k RPMs and let it coast down. When do you get that crack? If this can be narrowed down a bit, you could play with the Closed Spark settings and suck that crack back into the head a bit. Need more info.

 

Backfire or reversion caused by the exhaust / motor sucking in air?