[Kerrjustin1245]

I put 2 1/4" harley drag pipes on my bike. They have small baffles that look like a washer that can be rotated other than that they are straight pipes. We rejected the carbs with dynojet kit. 175 main jets and the pin in the #4 notch from the top just like the dynojet set said to do in the booklet for straight pipes. We also changed the spark plugs and made sure the ICM was working properly. It runs pretty good while its choked but once you start running it normally you get loud popping only from the front cylinder. You can see the ignition happening In the lower exhaust pipe. The back cylinder never does it its only the front one. We have adjusted the AF screw every way it can go and it hardly makes a difference it does it on decel and idle and during steady throttle position. It doesn't seem to be running bad but somehow fuel is getting into that lower pipe from the front cylinder and igniting in the pipe. We don't know what else to do we did everything how we were supposed to. Please help

 

[TenDollarBill]

Are you sure you don't have a leak between the pipe and the head? That will cause those symptoms.

 

[KCochran]

Might want to try replacing the exhaust crush gaskets, my bike was doing that and I had 2 air leaks on the carb boots and 1 bad crush gasket on the front pipe. I"m by no means good at this carb stuff, but after the air leaks, I was also at the point where the a/f screws only very slightly made any difference, in out just whatever. I ended up having to clean and rejet my carbs, (made a HUGE difference) runs like a different bike! Now I'm waiting for parts I ordered so I can learn how to sync the carbs.

 

[Kerrjustin1245]

Well we changed the gaskets this morning because last night we did have a leak and the gaskets helped a bit but it was still having the same problem that was when I made this post. What we ended up doing was taking the dynojet 175 main jet out and replacing it with a 170 just on the front cylinder carb. Idk if this helped but the slow jet for that carb was a 43 we put in a 40. After we put everything together that made a HUGE difference. Now it still pops on decel especially when engine braking but I don't hear any popping on idle at all. And no popping while holding a steady throttle position. I think when I get some more money I'll go to a shop that can dynotune it and see if we can work out all the kinks. The sound on these pipes is better than any other drag pipes I've heard before. So I don't wanna go with anything different just maybe get my performance optimized. It's faster now for sure and my top speed is higher too

 

[7xclm]

Have you tried adjusting the a/f on the front carb. Dyno tuning will definitely help.

 

[Kerrjustin1245]

Both carbs are set at 2 1/2 turns. Adjusting the front one didn't change the popping habits so left it at the recommended 2 1/2 turns