I have a 2006 1200 xl custom sportster with the 3 inch Vance and Hines slip on mufflers the baffle design is called the replacement style baffle with low restriction ( just slightly more than the competition baffle). I want to create just enough backpressure in the pipe to stop the popping on deceleration. I am planning on welding a washer to the inside end of the baffle to reduce the pipe opening from 1.5 inches to 1 inch hoping to create just enough backpressure during deceleration to stop the popping. I like the sound and performance and do not want to effect that to much. Has anyone done this before and what were your results.

 

You might also need to make it richer on the overrun as that is often the cause, too lean on the overrun.

 

X2. What he said.

 

What's an overrun???

 

Damnifiknow

 

I don't know how you get the computer to set the gas to the pistons on my old bikes the book said to warm the bike, ride to hiway bring the bike to 55 mph let off throttle if it backfires through exshaust its too rich, if it backfires thru intake its too lean then you changed your jet in carb. I'm sure theres more to it for the new bikes,but ya got ta start with the basics. SUCK SQUEEZE BANG and BLOW

 

Damifiknow in dictionary: The movement or extension of something beyond an allotted or particular position. You were on it

Using the engine to slow down with the throttle closed, carb is on idle circuit with exhaust reversion being pulled back into the cylinders causing a really really lean condition.

I have to keep my 127" idle circuit rich because the 3" muffler will pull air back in and spit out the carb if the idle AFR is normal.

On the main question, yes no back pressure will allow reversion to pull air back like you are thinking but also need to know your jetting and make sure you don't have a intake seal leaking.

On welding a washer in is going to be trial and error, more back pressure will move the power down lower and take away from the big side. Put the washer in and see if it strangles it, you can start opening the washer up from there. If you hit it right you can get power from low to high, that is why exhausts cost so much because they try to figure this out for us