Where is the idle channel/s from the venturi connecting to the idle tube and jet located on the Zenith 35/40 Carburator

Orange flame is not enough air in the gas air mix. You have a spider nest living in the venturi tube and nozzle. Weber sell a special brush. The venturi tube is between the gas control knob and jet and the burner.

your pilot circut is clogged. Take out your pilot jet (this is the jet closest to the cylinder) Be sure to spray carburator cleaner thru this jet until the stream is heavy and solid. Next insert the tube from your can of carb cleaner into the hole the jet was in and spray until it comes out in two locations in the carburator. One in the throat of the carb and one directly under the front edge of the slide. Go to the back of the carburator and you'll see a couple of holes at the bottom edge of the carb that mounts to the air box. these are vent holes. Spray cleaner into them and find the hole that vents the pilot circuit and insure it is not clogged. Once all of these are cleaned your bike should run as if new. Good Luck.

More than likely, the idle (pilot) jet is partially clogged. This is common when it will idle fine with the choke on, but won't idle without it. Sometimes a fuel treatment will clean the carburator, but not usually successful in cleaning the idle jet. Usually it requires removing the carburator bowl and and cleaning with the use of a gauge wire. The idle jet is usually recessed (next to the main jet).

A good video to show a generic carburator rebuild can be found at this link: http://www.youtube.com/watch?v=exa467_eoXw The guy goes through a pretty detailed description while going throught the process. The carburator will not look exactly like yours, but it will be similar internally.

The main issue is usually the jets get clogged due to gas sitting in the bowl for extended periods. the simplest solution is the remove the carb and remove the bowl and needle and float. Then, if possible, remove the main jet and air tube and also the idle jet (the smaller one ) (remove the jet from the bottom and gently push the air tube out from inside the carb body). Then clean the jets in carburetter cleaner in a glass jar.over night.
Take a piece of electric "zip" chord and strip back the insulation to expose the wiring which is very fine copper . use one of those strands to clean the jet until you can see through it and see no deposits or roughness. do the same for the idle jet. reassemble take care on the air tube because it is likely "keyed" in to a certain alignment.

Check the amount of fuel running from the connector line at the carburetor--it should run out as thin stream. If it just drips, the fuel filter ( a fine brass screen just above the bowl at the shut off valve) may be plugged. If ok, then remove the float bowl, the main jet, and the emulsion tube that runs from the rear of the jet out to the venturi in the center of the carburetor throat. Look for a short brass tube sticking into the venturi--use the flat of a screwdriver to gently press down on that short projection to drive the tube out of the bottom. Soak this tube and the jet in carb cleaner--make sure all holes are clear. Don't use wire or needles to poke into the holes--use toothpicks or other softer materials. Hope this gets you running again!

Carburator Theory and Tuning


For some reason everyone seems to think tuning a carb is just real easy. Change a jet or two and boom, your there. Yeah, right ! There are quite literally millions and millions of jet combinations. A rough check on Bing carbs shows there are at least 13,860,000 different combinations of jets. If you are going to change carbs you'd better be prepared to spend some time and money on the job.
If you look at a carburetor, you will notice a rather large hole going from one side to the other. This is called a Venturi. Air passes into the engine through this hole (Venturi). As the velocity of the air entering the carb (and then the engine) increases, it's pressure decreases, creating a low pressure or vacuum in the venturi. This vacuum moves around in the venturi, as the throttle is opened, and sucks gasoline through the different jets in the carb. The gas then mixes with the air going through the venturi. The way the jets are made causes the fuel to vaporize as it goes into the venturi. Where the jets are placed in the carb and where the jet's outlet is located in the venturi, determines what part of the throttle opening that jet controls. The idle jet system (comprised of pilot air jet, pilot fuel jet and pilot fuel screw) controls from 0% to about 25% of the throttle opening. The throttle valve controls 0% to 35% of the throttle opening. The needle jet and jet needle control from 15% to 80% of the throttle opening and the main jet controls 60% to 100%. This means that when you open the throttle about one eighth of the way open, all of the gas/air mixture going into your engine is controlled by the idle jet. As you can see, the different jets over lap the operating range of each other. That is, the jet needle starts to effect things before the effect of the idle jet ends. This is something to remember when working on carbs... everything is interconnected. Change one thing and it will effect other things.
OK, let's go over the different systems in the carb and see what they do.

1. Fuel level. The fuel level is controlled by the fuel floats and the fuel float valve. The floats are hollow or made of something that will float on gasoline, such as cork. Part of the float presses against the float valve, sometimes called a needle and seat. Most times the part of the float that touches the float valve needle is bendable so you can adjust the level of the fuel in the floatbowel. All plastic floats are not adjustable. If this level is way too high, gas can leak out the carb overflow tube or into the engine. If fuel gets into the engine it will thin out the engine oil, ruining it's ability to lubricate. This will, sooner or later, blow up your engine ! If a full tank of gas in the evening turns into a half tank by morning, check your oil. If it's thin and smells like gas, change it and replace your float valve and/or check your fuel level. If the oil is OK, check under the overflow tube. If it's OK, then check where you are parking your bike 'cuse someone is walking away with your gas ! If your fuel level is just a bit high, the mixture will tend to be a bit rich. If it's low, the mixture will tend to be a bit lean. This is because a high level takes less vacuum to **** fuel into the engine and a low level takes more vacuum to do the same.
   
   
   
2. Pilot or idle jet system. The idle jet controls the idle and on up to quarter throttle, give or take a bit. On some carbs, like Mikuni there is an air jet too. In conjunction with the idle jet there is an idle jet air screw. This screw leans or richens the fuel mixture for a smooth idle and on up to one quarter throttle. From the idle jet, there are little passages cast into the carb that lead to holes just in front of the throttle valve or plate. There can be just one hole or there can be several, depending on the carb design. They effect the mixture as long as the vacuum, in the venturi, is over them. As the throttle opens further, the vacuum moves to the needle jet and jet needle.
3. The Throttle Valve. The big slide that opens and closes your throttle has a bevel angle cut in one side of the big round (can be flat, too) slide, toward the air cleaner. This angle comes in several sizes and helps control the fuel mixture from idle to about 35% open throttle.
4. Needle Jet. This jet doesn't really even look like a jet, but it is ! It controls the fuel mixture from 15% to 60% open throttle. It sets in the center of the carb, right over the main jet.
5. Jet Needle. This is the needle that rides in the throttle slide and goes into the needle jet. This needle controls the fuel mixture from 20% to 80% open throttle. It can come in many different sized tapers. Sometimes, one needle can have several tapers on it. The top end of the needle has grooves cut in it, usually five, and you can move the little clip on the end up or down to lean (down) or richen (up) the mixture. Most late model bikes have needles with only one groove cut in them. This is so you can't richen the mixture, thereby keeping the EPA happy.
6. Main Jet. This jet controls the fuel mixture from 60% to 100% open throttle.

Remove the float bowl again and remove the BRASS Jet in the bottom of the venturi throat. Clean the pin hole of the Jet so that you can see through it. DO NOT force anything through it. Just clean it. Underneath the jet is the venturi tube itself. It is also unscrewed with a screw driver. Remove it and clean all ofthe holes in it. Then reassemble tube and jet in to the venturi. Check the BOWL NUT for 2 holes. If the holes are clogged your engine will suffer from a lack of fuel. Lastly check that you have FUEL flow from the tank to the carb. If the tank outlet hole is clogged you will also have a lack of fuel problem.

Hi and welcome to FixYa. I am Kelly

Most likely the JET orfice in the bottom of the carburator venturi throat is clogged. I am assuming you have a 5.5 Hp Honda motor but even if it is not the procedure is the same.

1. Turn off the fuel supply selector

2. Remove the float bowl by taking out the mounting hardawre. The nut / cap screw on the very bottom of the float bowl has holes in it. Make sure they are clean.

3. Remove the "Brass" JET from the bottom venturi tube and clean the orifice. You should see a pinhole of light through the hole when it is clean.

4. Remove the venturi tube just above the jet that is also brass. The throat of the venturi tube and the 2 side holes must be clear.

5. Use something like a spray paint can lid to catch fuel and then briefly turn on the fuel supply. The fuel should flow at a good rate though the float needle and seat assy. GENTLY lift the float to the raised positon (level) and confirm fuel stops. Then loet it lower again noting fuel flow. TURN OFF THE FUEL selector. If you do not get any fuel at this point check the bottom of the fuel tank for obstructions at the tank outlet hole. Once you have verified fuel flow.

6. Reinstall the venturi tube

7. Reinstall the jet

8. Reinstall the float bowl making sure upper and lower gaskets are in place.

9. Turn on the fuel and wait one minute (check for leaks)

10. Start the unit.....

(Complete)

Thanks for using FixYa.

Kelly

honda jets thread into the main venturi where the float bowl bolt goes. you jut need a blade/ flat screwdriver to thread it out. becareful they are only brass and thread it out and the emulsion tube should come out as well fairly easily. you may need to look inside the throat of the carb and just push the nozzle tube out. plus under the plastic idle adjustment screw there is a black plug and thats the idle jet,

Not uncommon for a HD to occasionally pop back thru the carb. If intermittent I would not worry about it. If frequent, you probably pinched the diaghragm when you installed it and poked a hole in the rubber. If it's OK, try gettin a kit for the carb that has new jets, slide spring and drills. Thunderslide or Yost power tube works well. If not available in your area, re-jet the slow speed jet to a 45 or 48. Leave the main alone. Enlarge the hole in the slide to 1/8". NOT the hole for the needle!! It's right beside it. Remove the carb for the next modifications...Remove the plug in the idle screw well. (Located under the carb close to the intake manifold. A tall skinny tube running off the carb body.) Drill a hole in the plug and use a screw and pliers to remove it. Re-install carb. Turn the idle mix screw (with a skinny screwdriver) until you get a good idle with the engine hot. Re-adjust idle speed to about 1000 rpm.