After hours of internet searching I want to put together my own topic. I've seen so many partial answers, or people not exactly putting what fixed their situation in the end. It seems to me there are so many different variables that can attribute to a coughing CV carb so here's my story and details. I need some advice!

2006 XL1200L
16,XXX Miles
Stage 1, K&N cone filter, cycle shack slip ons
Bumped 42 pilot to 45, main is 180
Rebuilt carb, new gaskets (CVP rebuilt kit), accel pump, NEW Jets, did not clean old jets (threw away).
EZ-Just mixture screw (packing is not missing), about 2.5 turns out
New spark plugs (HD plugs), gapped at .40
Fresh 91 octane gas with a small amount of sea foam in the tank (just in case)
NO INTAKE LEAKS! I put in fresh seals when I did the stage 1 and tested with WD 40 - no idle change
Idle speed set around 950-1000 RPM (no tach. im guessing)
No error codes

So a few other details.
I've been riding it in cold weather. Took it out at 17*F and it coughed like hell. Replaced spark plugs and went riding today at ~45*F. was better but still stumbling off idle. Coughing is off idle, rarely I'll get a fart while cruising about 45 MPH. typical if I keep the RPMS up, it launches and pulls just fine. Slight popping on Decel.

I also noticed sometimes it will slowly return to idle. This tells me that my AFR is slightly lean. Correct? Also a couple of instances where the idle would actually increase when I'm not touching the throttle. I havent check the fresh plugs after riding today but when I pulled the old plugs they were black and sooty (rich)

My concern now is that I may have pinched the diaphragm when I took off the carb top cover. What are some symptoms of a torn or pinched slide diaphragm? I checked the action of the slide when I put the carb back together and it made the sucking noise and operated smoothly unless I really pushed up on it fast (and I mean fast!) then it sort of stumbled I guess is how I would describe it.

I also have not checked the negative battery terminal, I heard this also might exhibit some of the same symptoms

I have a new Crank position sensor just in case as well, but I was told by 06 this issue was all but fixed. Also coughing happens when the bike is still not quite up to operating temp.

With all that I've been reading I probably forgot some of the things I have checked already, so if I have missed something else please let me know! I had no idea these bikes were so touchy!

 

I should also mention, exhaust is torqued to spec with fresh screamin eagle gaskets, no exhaust leaks either.

 

I just took the easy way out and sent mine to the man that knows CV carbs better than anyone I've ever heard of. You just tell him how your bikes configured and he'll send you back a perfectly rebuilt & tuned CV Carb.

Sorry, but that's all the help that I'm able to offer.

 

Appears that you've covered most everything. Try 3 turns out on the mixture screw. Idle should pick up, so then back the idle adjust down if necessary.

 

You've already bumped to a 45 so the transfer ports should be getting plenty of fuel just off idle... though the 42 should have been adequate for a stock bike. Intake gaskets are replaced... that's very important. Try opening up your idle mixture screw a little more to see if the cough goes away, no more than about 3-1/2 turns max... but with a 45, you should be well in the proper AFR right now. I would suggest shimming your needle .020 and re-adjust your idle, that should cure it.

FWIW: my '05 is running the stock jets 42-180 and I've replaced the stock needle (N4NN) with an N65C shimmed .038 and that pretty much solved all the lean conditions being experienced off idle.

 

I tried the idle drop method today. Set to correct idle speed again (think I had it set high before) Couldnt get it to drop on the rich side but I tried 3 turns out and only 2 coughs. One when she was cold, and another when I blipped the throttle once at a light. Pulled perfectly off the line. I was under the impression that 3 turns out was too much

I soaked my intakes with WD40 once again to double check for leaks, nothing.

It was a little bit warmer today so maybe that had something to do with the bike running better. I added seafoam to the tank last night and road her maybe 15 miles today, she ran great! Maybe I missed something when I cleaned and rebuilt the carb.

I was under the impression that maybe I was running rich already but I guess it was just lean mixture, I havent checked the plugs yet, ill probably get to that in the next couple days. Maybe I should up the pilot to a 46? everyone is telling me that a 45 is plenty but maybe I could up the pilot and go in on the mix screw.

 

Sounds like your close. I’d leave the 45 jet in there and tune what you have using the mixture screw.

 

Im thinking you're right. it's cold out right now so this summer once it warms up I bet ill be able to turn in the mixture screw. I've been told that the colder it is the leaner the bike will run? Something about there being more dense oxygen filed air in cold temps.

 

Some others will disagree with me, but you may be giving your bike too much air with that K&N cone filter. I experimented once with an open K&N filter I was running. After trying a number of things to correct the same problem you’re having, I covered about 70% of the filter with masking tape … problem went away. I still run that filter (with no masking tape) but with the stock ham can cover installed. The bike runs perfectly.

 

You know I kinda thought the same thing. It seems like she's really sucking gas because of how much fuel I gotta put into it just because of the filter, but I dont see any signs of it running rich, only running lean. I'll have to run it empty, do a full fill and calculate my MPG. I bet that'll give me a better Idea of what's going on.

I took it out today and it was COLD out side! She was a bear to get going. Had a couple coughs when still warming up but after that the off idle throttle response was pretty good. Now I was experiencing coughs at mid RPM cruising speed, around 45-50 MPH. They were rare and not too annoying but they were present. I'm still trying to disprove this cold weather theory I heard, but seems to me my bike is cold blooded.