I purchased a 2007 1200 Custom with Screaming Eagle mufflers ( I believe them to be just slip ons) and the bike back fires or pops at times when letting off the throttle .Is this normal for the bike with these mufflers?This is the first Harley I have ever owned.

 

You probably have a tuner of some sort on there, and if so, then yes, it's normal (meaning 'common' rather than 'right'). It generally isn't an issue, so unless it's amazingly annoying, don't worry about it.

 

Having no experience with these mufflers myself except for what I've been reading on this forum I would have to suggest you check out the air cleaner type (stock or higher flow), has the bike had fuel management upgrade to compensate the intake and exhaust changes? Once you start making changes from stock in this department there is usually something else that must be changed to retain the balance between the two. It appears that the general rule is, if you go with higher flow at one end the other only you're ok. If changes are made at both ends, fuel delivery will be an issue. I can't really offer anymore technical advise than this but I'm there are plenty of others out there that can. Good luck and ride safe.

 

Air filtration system is stock.

 

I have a 2006 1200 Custom with Screaming Eagle II mufflers on it and it doesn't pop or backfire when I let off the throttle. They are slip ons. The 06 has a carberator, this might be the difference. I can't tell alot of difference in the Screaming Eagle II and the stock mufflers.

 

Are you certain? The SE A/C uses the stock "ham can" cover, and looks stock, but deletes the back side of it, and uses a better filter.

 

Sounds like an exhaust leak. They do not normally backfire. Start there before messing with anything else.

 

I noticed a BIG difference between the SE II's and stock...

 

I bought the bike from the original owner who had the mufflers installed by the dealer at time of purchase when new.Air filtration system remained stock.

 

Ditto...if these are SE pipes vs. complete exhaust swap then check the header bolts (tight & no soot/leaks) and pipe clamps. They should've used HT silicone on the pipe joint/clamp, but sometimes dealer cust corners too... Also, you can turn bike on & feel/listen for air leaks, but be careful of the hot pipes.