Let me throw this out there, and I apologize if it sounds rather stupid. I have a 2000 Springer. It has a 40 mm CV carb. It is a high compression Screaming Eagle heads ported to 113 ci with compression releases. The carb has been fully reconstructed by a carb specialist. It also has a Dynatek Dyna TC88-2P electronic ignition. I have tried every one of the sixteen of the advanced curbs, but the issue continues. When cold and with the enrichener partly out or fully out, the bike sneezes thru the carb every now and then.

I have confirmed that I do not have a vacuum leak at any of the manifold or carb seal. I have read on these forums that one of the reasons for the sneeze is likely a lean condition. I believe I have dialed in my carb settings according to the Joe Minton tuning instructions and have set the mixture screw at 2 1/2 turns out plus 1/8. I have gone as rich as I can on the mixture screw because of its already rich condition. The carb has a 48 pilot and a 190 main. I have also brought down the size of the main and the pilot, which would lean it out, but could also cause the sneeze. The new Champion plugs continue to be fouled in just a few miles, and they show a rich condition.

I understand that the manifold Absolute Pressure Sensor (MAP) works kind of like the TC-88 in that it advances the ignition. Could the MAP be working in conjunction by enhancing (advancing) the settings of the TC88? Can the MAP be disconnected (I suppose it has one, but I really don't know)?

 

i do not believe it to be ignition related. the map sensor alters the timing according to engine load unlike the voes which is either on or off. that ignition uses all stock sensors and yours has the map if it is stock. plugs and wires can fool you and i avoid champion like the plague! even specialist have been known to screw up.
one mistake that is common is not having the initial idle screw, not mixture, correctly set and trying to compensate with the mixture screw. most will start with the idle then transfer and the wot settings.
i prefer the opposite since the wot is easily set and has nothing to do with the lower two. next will be the transfer to get smooth transfer to wot. idle becomes last. start with stock pilot jet and then work upwards. my machine has a 45/200 (custom main)
then make sure the enrichen valve works. also, no air ports on the carb throat are covered. seen a guy have issue with this due to the way the cleaner was mounted.
the mikuni site also has tuning manual.

 

How does the bike behave when fully warmed up (ridden at least 10 miles, not run in the driveway for 3 minutes). If it behaves as it should after being fully warmed up, you might have to just live with it. You've got a build build with a little stock carb, the carb will work, but you cant expect it to have the same manners as a stock bike.
m
how long are you running it to get your symptom?

 

By the way, I had to change my account information and somehow I got into an old account, hence the name change. Also, the carb is a CV not a Mikuni, if that makes a difference. When I tuned it, I had the idle at about 950 to 1000 rpm, as suggested by Joe Minton ( a CV carb guru). I have no doubt that the carb is set to its sweet spot with the fuel mixture screw at its present position, which means it is not set too lean or too rich, but the spark plugs tell a different story.

The sneezing (or coughing, for lack of a better word) only happens maybe once in ten start ups, or more, and when it does, it is a somewhat minor sneeze, about a 3 in a scale of 10, but then the engine goes ahead and starts up. This only happens when it is cold, never when warm or hot, and only after it has been sitting for several hours, and mostly the first start of the morning. Once I feel that the engine is warm, I gradually begin to push in the enrichener, to where it runs smoothly and the best, then push it in all the way and continue to let the engine warms up until I feel it is ready to hit the road. This warm up process only takes about three minutes at the most. Once at speed, on the road, it runs great. I could not expect better.

Although I don't know what gas mileage I am getting, that is not even a concern of mine. The last tank of gas was 87 octane because that is the only gas I had at the time, and I just changed back to 93 octane, which is what I always used to put in it. I don't remember if the sneezing started with the 87 octane. I hope to make it run ever better with that 93 octane gas (Ca), but I might even try the 97 octane just to see how it runs. I also use Sea Foam every now and then. I just wanted to see if I could get the spark plugs (Champion RA8HC) to not get so fouled up so quickly. If it is in the nature of the beast, I guess I can live with it.

 

jpeg of the plug would help. might need a diff heat range. octane should not be of concern at idle.
if you have a lumpy cam, you could have cylinder fill issue but that by itself should not foul the plugs.
you could put the system on an o-scope to see what is happening, low coil saturation will cause this.

 

Attached are front and rear photos of the Champion RA6HC spark plugs that I just took off. It now has Champion RA8HC plugs, but I got the same results. I previously also tried the Harley-Davidson brand of plugs. Also tried the NGK Iridium plugs, All had the same results. The bike currently has a newly installed Feuling cam plate and Feuling oil pump, new chain tensioner and Screaming Eagle SE266 cams. The cams were installed by one of the previous owners when the bike was CNC ported to 107 ci. I believe this cam has high lobes and is too noisy for me, but it is what it is, but I wish I could replace it with a much milder cam, but I don't know if a less aggressive cam would be compatible with the high compression of this 113 ci engine. It also has a new dual coil with a primary resistance of less than 1 Ohm that was required by the TC88-2P ignition system, in addition to new Screaming Eagle spark plug cables.

 

If all you are doing is starting the bike with the enricher on.. Plugs will turn black like that.

Typically a cough is caused by not enough fuel and not enough timing. The issue could be the MAP sensor stuck at 100 kpa which makes it run the short curve and could cause the cough.. With it stuck at 100 kpa, the ignition module is not smart enough to declare an error. Don't know if it's the problem.. You could try and replace the map.. But it could easily be something else.

Personally I don't have any experience sit the Dynateck or the CV40 on a big motor. I will say that running a snorkel AC tends to make the bike run rich with a long cam at low throttle.. A trusted bud named Tracy Spencer used to write a column for Hot Bikes indicated that at one time he found running too rich at low speeds could cause the cough.. I've not seen it but believe it's possible..

I would go back to the 45 pilot and see if that helps.. If that it doesn't make it worse replace the map sensor.

Add:

I'd make sure the CV doesn't have a "Needle Kit" in it.. Or washers under the needle.

 

The carb has a CV needle with no washers. The bike will only start with the enrichener fully out when cold. When I ride off, the enrichener is always fully seated. I just need to put more miles on it for extended periods of time, at full highway speeds. I think that will help blast off or prevent the fouling of the plugs. But, yes, I will install a 45 pilot and see the results, before I even consider messing with the fuel mixture screw. If the spitting does not increase, then I am good to go. My practice is to only do one thing at a time; either the pilot or the mixture screw, but not both. Thank you all for your input, and I am off to hit the road, as soon as the rain stops here in sunny southern CA.!!