Another Twin Cam 88 with Backfire Thru Carb

[byf41]

I bought my 2003 FXDL new in 2003 . I pulled out of the dealership driving It home , theres a stop light right In front of the dealership . First time I cracked the throttle It backfired through the carb and died . Had It In the dealer so many times the zone rep offered to buy It back and put me In a 2004 with FI . I kept It and have been trying to get It right , off and on ever since . Ive got SE slip on pipes that I bored larger , 16952-99B SE heads , 44MM carb , 25149-00 cams/push rods , 31710-01 coil/module kit , plug wires . It runs WAY better but I still get the occasional cough through the carb . Ive got a #50 slow and #200 main jet In It and I think the original 44mm needle and spring as I recall , about 2 turns out on the air/fuel . I have It Idling at about 1100-1150 which I know Is on the transfer ports , but If I lower It the problem Is worse . I guess my question Is , should I go to a #52 slow jet , seems a bit much ? I thought about changing needles or adding a shim but from what I understand the needle Isnt In play off Idle , cant find a decent performance needle anyway . I wonder If Im fighting a problem with my map sensor/timing but honestly don't know how to check It . No vacuum leaks and float level OK . Any opinions or recommendations would be appreciated .

[Hossamania]

Does it do it whether cold or warm? Does it do it just off idle when cracking it hard, or when rolling down the road and a slow or intermediate or hard roll on?

[Hossamania]

Is the accelerator pump working properly, a good strong stream shooting directly into the throat when you twist the throttle?

[byf41]

Accelerator pump has a nice strong stream . It will do It warm or cold , but very seldom when the choke Is on . Once youre rolling It will almost never do It , 99% of the time Its when cracking the throttle from Idle . Sometimes when you roll on the throttle easy It will do It but not often . If I drop the Idle down to spec (950-1050) It does It more frequently . Classic symptom of lean mixture IMO but I hesitate to go to a #52 slow cause It seems like a #50 should be sufficient ?     

[Hossamania]

Have you ever had it on a Dyno for a tune, or at least run to see how it reads?
You could try a shim under the needle to see if it helps. If not, pull it and try the 52. You are right, it is a classic symptom of lean condition. While cv44 carbs are all the same, they are not all the same.
Could it be a condition of the pipes not playing well with everything?

[speedzter]

If you set your idle low (warm) does your mixture screw have any affect ?
You have obviously tried to richen the screw, say 3 to 4 turns out ?

[byf41]

I have the A/F at 2 turns out cause that's the sweet spot with the current jetting . I have turned It out some but have not had It out to 3-4 turns as I recall and I believe that was at say 1100 rpm . I verified It has the N8EL needle In It now . I do have a #52 slow and some larger main jets In hand , as well as a .034 needle shim I took out of my stock carb when I was trying to make It work . Never had It on a dyno . Guess I should have documented It better . 

[clifford2004]

Intake leak ?