My new to me FLH has Vance & Hines exhaust, no other mods that I can discern. While the whole package runs and rolls well, I have some thoughts and questions about these CV carbs before I decide to go all Mikuni on her.
1) now and again, it has the old EVO sneeze thing, Does a little carb pop at.low.speed throttle up, not huge unless it happens when you are starting from a stop and then it can be a bit shaky. My 91 did this as well, but the bike changed hands before I had the chance to address it.
2) I have a definite flat spot in higher gears, when throttling up it is.pretty logie. Again, it runs Ok but merging onto an interstate I'd like a bit more response
3) when decelerating, there is a decidedly good deal of burbling and low.level backfire from the pipes, not anything shotgun-like but a good bit of popping and farting.
Again, I'm not a CV familiar guy, so some ideas about cures to get better throttle response and all without a lot of.experimentation would be appreciated

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Post this in the evo section. Those guys know these old bikes.
Some will say convert to an s&s and I happen to agree with them. Otherwise, sounds like you need a larger main jet with those pipes.
You may be running a little lean from the sounds of it.

 

Sounds like it might be starving a little. Drill out the idle mixture cap to access the screw and bring it out a 1/2 turn or so.... If that makes no difference then up the pilot jet one step.... One step at a time is critical to tuning.