I have a 2003 Road King EFI that has a high flow air filter, V&H true duals with oval slipons, a S&S 510G cam, and a V&H Fuelpak. Since putting on the true duals about a year ago, I occasionally get a really loud "bang" backfire or small explosion when starting the bike. Not always, but frequently enough to be a concern. Usually happens when the bike is cold and has been on the side stand for a while, but it's also occasionally happened with a warm engine. Other than that, the bike runs great. Any thoughts as to what's causing this? Thanks in advance.

 

Try running an Autotune session or two on your fuelpak .Adding the true duals likely changed your AF ratios. You may be able to get closer with resetting your base settings on Fuelpak also.

 

I did retune per the V&H web site and also contact them and they had me adjust a couple of numbers. I have the old school LED Fuelpak, so no autotune. Just bought a Power Commander V. Hoping that fixes things. Just concerned that fuel is leaking by something.

 

My 04 RK does that occasionally, I have a PC3 with stage one and 510G cams. Maybe happened 15 times in 75,000 miles.

 

Check for air leaks. Intake, exhaust, vacuum.