Yes - Another Carb thread

[whompditty]

Hey All,

Ok, I have been sniffing through all of the threads and found quite a few carb threads out there, lots of info, but am hoping some folks can document actual results that fixed the dreaded carb cough.

I have a 2007 K-9 with a 117 S&S (it's black so it's the fastest one) with 1800 miles. ( I am the new owner)

Here is the scenario - lots of power and great throttle response. But...

Going down the highway at 70-75- running 6th gear at 2500 rpm. Every so often I get a nasty carb cough/sneeze. Feels like the bike lurkes a bit. Also, about 40% of the time it back fires when gas up and start the bike.

I have stock pipes, stock carb, stock air cleaner. I live in Raleigh, NC which is 350 feet above sea level.

Everything on the bike was stock so I am assuming so are the jets. I don't know where the ORIGINAL owner had the bike as I bought it from the dealership he traded it in in at. So if you are counting, technically, I am the third owner.

Anyway, I have seen quite a few "try this" responses, but has anyone found the true fix to the carb cough at highway speeds?

Since I have stock jets, what should be the first thing I do, increase the main or play with the accelerator pump?

Thanks again for any responses.

 

[woodbutcher]

i'll let somebody else try to handle the cough, but in comparison, i also have an '07 k9 (black cherry-the good looking one) but have never had the coughing and everything is pretty much stock. did change to V&H BR and the jets were changed years ago. occasionally does backfire after re-cranking but i attribute that to built up vapors in the exhaust at fire-up.

might want to get it dyno tuned by a competent tech.

 

[330-DAN]

I think the backfire is to be expected, mine does the same at times and the guys I ride with also do I've noticed. If its all stock I may wonder if it could be a tune issue due to the elevation. Just a thought, I know when I used to drag race the elevation messed with my tune. I know its a little different but a thought.

 

[Th3InfamousI]

Bike runs lean from the factory due to EPA regs. Most guys up their Intermediate jet from the stock .0295 to a .31 or .32 and off you go, no more sneezing.

 

[Knuckles]

Bike runs lean from the factory due to EPA regs. Most guys up their Intermediate jet from the stock .0295 to a .31 or .32 and off you go, no more sneezing.

X2

 

[Brew]

I agree, mine ran lean from the show room floor all stock and had the same cough. I put V&H 2 into 2 and a spike air cleaner on and re-jetted to a 31 int and 78 Main and all is good. As suggested put it on a dyno and have it tuned...:2thumbs:

 

[BWG56]

Bike runs lean from the factory due to EPA regs. Most guys up their Intermediate jet from the stock .0295 to a .31 or .32 and off you go, no more sneezing.

X2 on the intermediate but only after you tried to adjust according to S&S carb. set up. Check out S&S website.

 

[bombtosser]

These guys are right. Dino it or start upping the intermediate jet size. Don't forget to adjust the carb after each jet change.

 

[Zachusmc]

This should help








Watch the Super E & G Carb
Basic Setup video


1- Verify carburetor is set to stock settings:
a- Idle Mixture Screw, 11/4 turns from lightly seated.
b- Idle Speed Screw, ½ turn clockwise from engagement point.
c- Accelerator Adjustment Screw, two turns counter-clockwise from seated.

2- Start bike, bring to operating temperature.

3- Set Idle Speed Adjusting Screw, clockwise to increase rpm, counter-clockwise to decrease rpm. Idle rpm range should be 950 to 1050 rpms.

4- Adjust idle mixture by turning Idle Mixture Screw slowly clockwise until the engine runs poorly. Slowly turn the screw counter-clockwise until it runs smoothly—if you go too far the engine will start to stumble.

5- With engine idling, turn Accelerator Adjustment Screw clockwise until it lightly seats. Snap throttle open—engine should stumble. Turn screw counter-clockwise ¼ or ½ of a turn at a time, until engine responds to throttle twist with smooth, quick response.

6- Ride motorcycle in various rpm ranges, and then try to maintain a consistent 40- to 50-mph. If the engine is popping or sneezing in the air cleaner it can indicate a lean condition. If you notice stumbling or sputtering it can indicate a rich condition.

7- Low rpm operation is controlled by the intermediate jet (#11) if coughing or popping is experienced below approximately 3000 rpm’s the intermediate jet must be replaced with a larger sized (richer) jet. If the engine is sluggish or does not want to idle smoothly a smaller (leaner) intermediate jet needs to be installed. Always readjust the idle mixture (#2) and idle speed (#1) screws after making a jet change.

8- To test the Main Jet, do a roll-on from 50-mph to 70-mph in 3rd gear. If the engine back fires or breaks up in the carb, increase the Main Jet size .004”. If the engine is flat or will not accelerate, decrease the Main Jet by .004”.

9- Since 2004 S&S Shorty carbs have been fitted with an adjustable main jet air bleed (#13). Changing this jet to one of a larger size will delay the signal to the main jet, therefore aiding with high speed tuning as described in step 8. This also aides with tuning an engine that is fitted with an exhaust system that is not intended for high performance.

10- NOTE: Drag or straight pipes can prevent you from obtaining optimum carburetor performance.

11- If the S&S teardrop air cleaner is being replaced with an aftermarket air cleaner be sure to remove the auxiliary bowl vent screw (#14). Never use a velocity stack on a street driven motorcycle! Poor throttle response will be experienced.

12- Always be sure to attach the hose to the overflow tube fitting (#6) and route it towards the back of the engine.

 

[Zachusmc]

Here is the link to the video
S&S Cycle | Carb Quick Guide

 

[Little-Boo]

70-75- running 6th gear at 2500 rpm . Maybe you should be in 4th gear if it's only doing 2500 rpm. :loony: :loony: I don't think it has anything to do with the Carb at all, drop it down to at least 5th gear and kick in the ass and you will see that nasty carb cough/sneeze go away :2thumbs:

Carlos

 

[outdoorsman26]

like carlos said you need to be runninig a lil more RPM!!! 3K is a good spot to keep it

 

[whompditty]

Ok - so this was a loooooong time to follow up on this, turns out the exhaust was loose at the manifold. Tightened them down and no more lurching. Now, I think I have a float issue with the carb. Whenever I pull over for gas, the next start is a loud pop. So, this will have to be investigated, but I am pretty sure it's a float level issue at the carb causing the backfire.

 

[FrankBDPS]

My 107 backfires at start up sometimes. Scares the shit out of a bunch of dumb asses who park too close anyhow! I love being annoying.
.

 

[Th3InfamousI]

Ok - so this was a loooooong time to follow up on this, turns out the exhaust was loose at the manifold. Tightened them down and no more lurching. Now, I think I have a float issue with the carb. Whenever I pull over for gas, the next start is a loud pop. So, this will have to be investigated, but I am pretty sure it's a float level issue at the carb causing the backfire.

My 107 backfires at start up sometimes. Scares the shit out of a bunch of dumb asses who park too close anyhow! I love being annoying.
.

Just out of curiousity when it backfires are you giving it gas on startup?

With the big-inch 103+ engines you are not supposed to open the throttle while hitting the start button it unnessarily increases compression in the engine.

Owner's manual states to give it 2-3 twist of the throttle to give it gas then hit start button. Specifically states NOT to roll the throttle when starter is engaged.

 

[woodbutcher]

see post #2, (occasionally does backfire after re-cranking but i attribute that to built up vapors in the exhaust at fire-up)

 

[FrankBDPS]

Just out of curiousity when it backfires are you giving it gas on startup?

With the big-inch 103+ engines you are not supposed to open the throttle while hitting the start button it unnessarily increases compression in the engine.

Owner's manual states to give it 2-3 twist of the throttle to give it gas then hit start button. Specifically states NOT to roll the throttle when starter is engaged.

Last summer was the first season I owned my Prosport.I knew it had some carb and starter issues. I have had Curtis do my starter and John did the carb. Thank for the good advice.I will watch how I start it. My first V twin so any advice is appreciated

 

[Viking]

…..With the big-inch 103+ engines you are not supposed to open the throttle while hitting the start button it unnessarily increases compression in the engine…..

103 is considered too small here. Opening the throttle DECREASES the compression.. However, with the S&S compression release, no throttle should be used during start, as you stated. Just FYI.

 

[pknowles]

This has nothing to do with your carb issues, but bone stock right out of the box, I am almost certain that red is the fastest color

 

[francoblay1]

This has nothing to do with your carb issues, but bone stock right out of the box, I am almost certain that red is the fastest color

I am sorry to say but... the fastet is the yellow!!!