it could be an airleak where the exhaust goes in to the head.

 

I have a stage one kit on my 2002 FLHT but the HiFlow K@N filter doesn't have a HiFlow backplate therefore restricts the airflow. you might want to check that.

 

A couple of things for you to look at, whenever an after market exhaust is put on or for that matter when ever the head pipe is loosened replace the exhaust gasket that goes between the head pipe and exhaust port. Do yourself a favor, their cheap. The same if you have "slip on" mufflers if loosened or removed replace the crossover gaskets. MoCo recommends the muffler clamps be replaced apparently they are only good once (I have never replaced mine =) but I can see little signs of leakage, not much though). Next check for intake leaks.The easiest way is to run the bike until it's warm, spray carb cleaner all around the rubber intake manifold. If it doesn't kill or make it idle high, you should be good. Intake or exhaust leaks will make your bike seem like it's running lean, in a way it is, your getting more air then gas. Once you made sure you have no leaks go for a ride. If you still have popping pull the choke (enrichener) about half way out. If the popping goes away you now know for sure you are still to lean. Now don't go thinking riding with the choke half way out is the solution, adjusting the carb really is easy. If you don't know for sure you may have to remove the carb. Check the bottom of the carb to see if the air /fuel mixture screw has been "revealed" (they come sealed from the factory, you know E.P.A. regs.) it should be with the mods that are already done to it. If its not don,t worry it's easy.If it is, back screw out to 3 1/2 turns (no more you don't want it falling out, bad bad bad) take it for a test ride. If that doesn't fix it then you need to go to the next larger size pilot (slow) jet. Stock is 42 I run a 45. These steps should solve 90% of stage 1 carb issues.

 

No baffles? You will get some popping, maybe quite a bit. You are also probably giving up some power under about 3,500 rpm. You can tune the carb silly, and it won't get rid of the popping. It is, IMHO, a condition of life with open pipes. If you lean it out to much trying to get rid of the popping you could leanit too much. The result could be overheating, pinging, detonantion, leading to engine damage, which is definately not a good outcome!

Do your plugs look rich or lean?

Check out the Big City Thunder site for some Thunder Monster baffles. They will restore the power curve, and also probably reduce the popping you are hearing. Probably improve the sound, also. The site also has a nice explanation of how the exhaust system works.

 

No baffles? (I have to read these threads better) He's right back pressure is your friend unless you are just going to drag race the thing low rpms aren't a factor but upgraded valves and pistons will be your future. However I still think you're too lean. Check your plugs, try the choke trick . Your valves will be much happier if you run some baffles or at least some torque cones. I think your V&H's will still sound nice but more importantly they will work like they're designed to. Good Luck

 

Too lean. Richer makes it go away. I disagree with drags and having to live with popping. I have 1 3/4" drags on my Sporty and have dynoed to pleasing muffled decel "pop" sound at 13.5 AFR with #48 and 175 main. Any bigger diameter of drags I will agree is better for WOT application vice cruising.