Carb farts in 883 Sportster

Hi, I'm new here and have a problem with my Sportster and would like some advice. I've read many posts with good clues in the forums but want to put my specifics in and maybe get a hint on what to be checked and in what order.



It's a 2001 883 XLH with SE 0 slip on mufflers and SE air intake. It was installed and jetted in 2004 and has run great for over 6 years until now this spring. The last thing I did before this started, was to clean and oil the K&N Air Filter.

Symptoms:
1. It farts through the carb, it's a lot when the bike is cold and even more when the weather is cold. It idles fine put the farts come when i'm at 1/4 throttle or when I hold engine speed steady for a while. It's a lot better with the choke pulled out but still farts. When the bike is hot the farts are not so severe, just pops occationally on steady engine speed.
2. It leaks a little fuel out of the air filter element.
3. Sparks are black.
4. When I'm still and idleing, sitting on the bike, and tilt it to the left side, idle speed goes down and it chokes and caughs. If I lean it to the right side the idle speed doesn't change.

I cleaned the sparks and adjusted the idle speed screw and it ran fine for a day. Next day it startet again.

I would love to get some advice on what to check and in what order. Hopefully I can get some here.

If your plugs are black, it sounds like your bike is way too rich. another thing that leads me to think that you are too rich is that you are getting gas spray. Have you done any type of engine upgrades other than the the slip on mufflers and intake? Did you rejet when you did this?? Do you know what you are running for jets???

I have a 96 Sportster that was an 883. I did a lot of engine mods on mine but this is what I did for jetting. I went to a 46 pilot and a 185 main with the needle shimmed. Also I would check your float level as I think we just had a post that was experiencing the same gas spraying symptom.

No upgrades since 2004. Then the SE air and muffler upgrade was done and the jets were changed out. Not sure what was put in, it was done at the HD dealer for the previous owner.

It has been running fine for over 6 years with the upgrades. How do i make the mixture more lean?

It could be that your jetting is fine then, but I am assuming that you have the factory vacuum fuel valve? this could be the culprit as well. I had a friend that bought the original tins from my bike and the fuel valve. he started having problems with his bike just like you are describing with having to run with choke partially out. If it is the jetting you would have to downsize the jets. Check into the fuel valve first though. I thought of the fuel valve when I was just out for a smoke.

Ok, fuel valve and floats. Sounds like a good advice. Is there any way of checking the float level without pulling the carb off and opening it?
What shall I look for regarding the fuel valve?

I suppose you could check float level without the carb off but will be a pain. I would take the carb off so you can see what you are doing better.

Quick question.. Do you have a factory Service manual?? If not get one...you will be glad you did.

I am sure Chucktx and HotRoadKIng will correct me if I made any mistakes so don't do anything just yet as I am sure they will chime in on this as well. I am not sure how to fix the fuel valve if it is that. I went to a gravity fed fuel valve when I changed everything on my bike.

By the Way....Welcome to the forum!!

I have the Factory Service Manual. Holding it right now
You're talking about the Vapor Valve that is located under the seat between the battery and the oil tank?

I'll not do anything until I have more action on this thread. Thanks for the welcome.

No I am talking about the petcock..

That makes more sense.

I'm going to take a couple of hrs ride now and see what goes on. Just cleaned the spark plugs and will check them when I come back.

Let us know!

Could be some dirt in the float bowl clogging a jet or a some varnish partially clogging a jet....did this start after taking the bike out of storage?? might be time to clean the carb and a new set of plugs.

Well, now i just did a 135 miles (217 km) drive at an average speed of 60-75 m/hr (100-120 km/h). Outside temperature was 37-50° F (3-10°C).

The bike behaved pretty good the whole time though I do feel like it's lacking power just a little bit, especially when I try to hold the throttle at even speed. Then it seams to lose torque. Accelerating and decelerating seems to work reasonably. The frizzle of gas out of the carb is still coming but either it spread more cause of the speed or it is a bit less than before. Occasional farts popped out but i hardly noticed them. I'm waiting for it to cool down a bit before I check the plugs.

Plugs looked ok. I put new in anyways. I'm gonna see how it behaves tomorrow morning when I cold start and ride to work. It's already 1:00 am over here so I'm off to bed. I will keep posting here about this and the next steps.

Wanna check for intake leaks but need a little bit more idiot proof procedures. You kind of have to talk to me like a six year old since english is not my language and we have bit weird language politics in this country. No words or mechanical terms are the same as in english.

I would take an unlit propane torch, start the bike. I like to have it at operating temp. When up to temp, open the valve on the propane torch,m do not lite, the go around all areas that you may suspect that may leak. Head gaskets, intake gaskets from the head to intake and so on.....You could use WD40 if you like but it will cause a mess....if the rpm's increase, that is an indication of a present leak....

When I took it out this morning and drove to work the bike ran with no problems. No farting and popping all the way to work. What I did was to change out the old spark plugs (Been in for 3 years) and put in new.


Old plug was this type


New plugs are this type

I was told yesterday by my friend that we had faulty fuel sold here a few months back and many bikers had problems with their plugs after that. Hopefully this will do the trick.

I still want to check for intake leaks even though the bike ran fine this morning. I do not have access to a propane torch so I guess WD40 have to to it. Am I understanding right that I should spray around the two joints where the manifold is attached to each cylinder and where it is attached to the carb?

Yes that's correct. You can use carb cleaner too... be careful not to let any spray get in the mouth of the carb when checking around the carb mount or you'll get a false reading....good to hear it was a simple fix.

I set the throttle to around 1500 rpm's and sprayed carb cleaner all around the manifolds and on the area behind the carb. there was no change in rpms.

The bike seems to run fine but it still sprays a mist of fuel out off the carb when I rev it up quickly. Is that normal or do I need to look into something?

Borrowed from another site....


"FUEL STAND OFF''....this is a characteristic of a internal combustion engine with a carb on it. It has nothing to do with your jetting or acceleration pump intake leaks or timing......it's a pulse wave that happens when a column of air(intake) traveling at 650 feet per second into a cylinder THEN the valve closes on this column of air. The column of air with a charge of fuel in it just doesn't stop, (who was it that said for every action there is a reaction?) any way when the valve closes the charged column of air traveling at a speed of 650 fts bounces off that valve and makes it's way to the other head where it bounces off that closed valve and the column makes it's way out through the carb....now here is where this gets interesting...the carb isn't too smart, It doesn't realize which way the air is traveling so as it goes over the venture it picks up more fuel in the column of air that already had a charge of fuel in it....when the column of charged air hits the atmosphere it's like hitting a brick wall so the air is reflected back into the engine as a little weaker pulse wave but since the fuel is much heavier than air the fuel continues out into the atmosphere soaking your air filter and the whole right side of the bike depending on how long you have the bike under a load at high throttle positions.
To witness this you can take off your air filter and do a few runs on the dyno and watch this STAND OFF happen before your eyes....a plumb of fuel will hover out side the mouth of the carb up to 8'' away depending on the displacement of the engine, cam overlap, and exhaust system used.
Now when you take the time to set up ''Intake Track Tuning'' this waisted gas can actually be pulled back into the engine and used instead of washing your air filter. Intake Track Tuning is using the pulse waves of the intake to assist in cylinder fill by timing the wave to hit the intake valve as it is starting to open...