i ride a 2003 Sportster 1200 custom anv. edition with roughly 23000 miles on it and it is "coughing" or "backfiring" through the carb and intake, NOT backfiring through the exhaust. I bought the bike in november and have already had the bike in the shop twice since then. first time i took it in was for the "cough it had. harley told me nothing was wrong with it at all and promptly decided to take some more of my hard earned cash. I did buy the extended warranty just for piece of mind more then anything else. anyways, after taking it the first time and being told there was nothing wrong i figured it was plugs or just needed to be rode. So changed the plugs, threw in some seafoam and got some riding done! well 2000 miles later i am STILL having the same problem. so i take it back in to harley and they clean the carb and replace the intake seals. i have no problem with this at all since my bike is carbed it would have to be done eventually. harley told me that the poping is gone and it will run alot better! well the bike ran great, for about 5 miles then the "cough" came back. the "cough" seems to only happen when i am going at a constant speed! im not gunning it, or slowing down. i am maintaining a constant speed! i notice it more in 3rd gear around 25-30 mph is when it does it more. it is not a constant pop or cough, it just happens randomly then will run fine until it happens again.has anyone had this problem before? any ideas? ive had people tell me that is just the nature of the beast, hell even harley said it. i dont buy it. ive owned hondas, suzuki's and alot of other jap crap bikes. they NEVER did this. and if they did a quick clean and some new seals fixed it. so Harley wants me to beleive that this bike is just made to run this way?i call BS. Im in the military and i dont have time or the money to keep putting my bike in the shop so Harley can continue to "maybe" fix it. i will be taking it back to harley so they can correct this hopefully since it cost me 220 bucks to get it done and it still not fixed.Once this is fixed i will not be going back to harley unless i have to! has anyone had any problems like this with a carbed sporty? and if so what did u do to fix it? any troubleshooting ideas? sorry this was so long im just frustrated.I live in socal and cannot stand not riding my bike! i appreciate any help at all!

 

Get a can of carb cleaner and spray around the intake seals to verify that you don't have an intake leak. Just because they said you don't, doesn't mean you don't........

 

Bike is way lean.Need to look uder carb and pull air/fuel ratio plug out back off about three turns.Put in needle from a 1988 Sport in plce of stock.You will be good to go.This is also in the carb section.

 

Agreed, if there is a leak you will get an RPM increase when you spray the manifold area. This was a pretty common problem on Shovels and Evo's.

 

Just need to adjust the a/f screw. Do a search and you will see. I have the same issues all the time right now. Its hard to keep the carb tuned right when its 39 in the mornings and in the 80's in the afternoons.

 

How many RPMs are you turning when it happens? Third gear and 25-30 seems like your RPMs may be low at that time. I'm assuming you haven't changed anything just before it started and the bike has has a relly good chance to warm up. Also, have you checked your plugs? Could be a cheap fix though usually coughing is caused by a lean condition. Also, as was stated, try spraying carb cleaner around the intake seals. If this is happening well after the engine is warmed up, one thought is to pull your enrichener out just a bit when its happening and see if it gets better or worse.

 

Thank u for all the help! I will try everything u all suggested! Ill post again with the results!

 

one other thing you might check...maybe water in the gas tank...drain a quart of gas into a jar and give it a good look...it doesn't take much water to cause problems...

 

http://www.nightrider.com/biketech/hd_cv_mods.htm Try this!

 

yup, my 03 sportster did the same thing. richen the pilot jet and pull the mixscrew out a couple turns out you should be good to go!