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After engine is started fuel flows out of carb vent tube

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Hi, Lou and the usual suspects are:
1. Damaged or restricted fuel tank venting system.
2. Loose float bowl screws.
3. Damaged float bowl o-ring.
4. improper fuel level in the float bowl.
5. Worn or dirty inlet valve or seat.
6. Damaged or leaking float assembly.
7. Particle contamination in inlet fitting cavity.
For more information about your issue and valuable "FREE" downloads that you will need please click on the links below. Good luck and have nice a day.
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Posted on Dec 12, 2016


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Why is gas pouring from the vent line when I go to start it

You don't say what kind of bike or give any other details so I will go with the obvious stuff first, I am guessing you might not ride it often or let it sit up for awhile. Gas pouring from the vent indicates that a float valve is stuck or the needle valve or seat seal has dried up and has fuel being forced around them as the fuel pump pressurizes the carbs. It is dangerous to run the engine with overflow as you could have a fire so your remedy will require you to pull the carbs to fix the problem.

Sep 11, 2014 | Motorcycles

1 Answer

Engine dies out after driving 1-4 mile on a 2010 honda trx 420

I do need more info.. BUT, #1 the main ignition coil could be going bad..when it gets hot (electrically), it starts breaking down internally, #2, could be a clogged fuel system,, the system is vented to allow fuel to flow through the petcock to the carb. If the fuel tank is totally sealed, it will vacuum lock. Let the atv sit for a few minutes, then it repeats this cycle? #3- make sure the vent tubes on the carb are clean and will flow air through them!! These are the three most obvious choices and a great starting point. Make sure your air filter is clean and in good shape!!!!!!

Jun 19, 2014 | RTO 200cc Full Size Four Wheeler ATV

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If I remove a yics plug from one side and prime with fuel, the engine will start and idle until prime is burnt. Why will fuel not flow. New tank, new peacock, rebuilt carbs, new gas

Hi, Burns193 always check fuel flow first to isolate the problem area otherwise the usual suspects are:
1. Fuel tank empty.
2. Fuel cap or fuel tank not venting properly.
3. Fuel filter clogged with rust or dirt.
4. Fuel valve/petcock not in the on or reserve position.
5. Vacuum line to fuel valve cracked, broken, pinched, or missing*
6. Fuel valve/petcock clogged or diaphragm cracked, cut or torn*
7. Fuel line from the fuel valve to the carburetor or fuel pump clogged, cracked, pinched, bent, broken, or missing.
8. Fuel pump not working*
9. Fuel line touching cylinder or head causing fuel to boil and vapor lock, repair by rerouting and wrapping line with convoluted tubing.
10. Carburetor inlet clogged.
11. Carburetor float or needle and seat stuck.
12. Carburetor not venting properly overflow line or bowl fitting clogged, pinched, or bent.
* If equipped or applicable.
For more information about your issue and valuable "FREE" downloads that you will need please click on the links below. Good luck and have nice a day.
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Apr 20, 2013 | 1982 Yamaha XJ 650

1 Answer

I have 120000 model engine on a troybuilt 566 self propelled mower. The engine will start and run for about 3-4 seconds and die. I have changed the spark plug,air filter, cleaned the fuel line, and...

You have done the correct things. This is definetely a problem with the fuel supply. Here are some other things to check.

1. Loosen the gas cap to ensure you don't have a vacuum in the tank. If you have a vacuum in the tank, it can prevent fuel from flowing to the carb. This is an easy thing to check, typically the engine will run for longer than 3-4 seconds when first started, but when restarted I have seen short run times like this. There should be a vent hole on the gas cap to prevent this from happening. If this is the problem clean the vent hole or get a new cap.

2. I don't know if this engine has a fuel pump, but the troubleshooting process is the same. Take off the hose to the carb and make sure you have fuel flow to the carb (use gravity if it doesn't have a fuel pump, or crank the engine if it does). If you have fuel, then the problem is in the carb (probably a stuck needle in the bowl assembly). Disassemble the carb bowl and clean the needle and seat with carb cleaner.

3. If you are not getting fuel through the hose to the carb, then you have a bad fuel pump or a plugged line.

Apr 18, 2011 | Briggs & Stratton Briggs Stratton Intek V...

1 Answer

When I start my bike, after 30 seconds fuel backs up in the fuel vent tubes and dumps out on the floor. It backs ups thru the air intake, fills the canister on the end of the vent tube, and over flows...

Float is sticking in one or more carbs. To narrow which one it is, drain each carb seperately,measuring the feul in each carb. The one with the most is the one the float is sticking on. Be sure that the top vent lines are not blocked or colapsed.

Nov 02, 2010 | 2002 Yamaha YZF 600 R thunder cat

1 Answer

Kohler engine starts but won't continue to run

if this engine is only runs on the choke and stops when its open sounds like a fuel problem !

make sure the carb solenoid is getting 12 volt to open up the main jet

check that the fuel cap is venting ?

check the fuel filter ?

check the fuel pump is causing flow when being cranked
if it has one

check the carby jets and emulsion tubes and air bleeds are clear and needle and seat aure not stuck closed ?

check the valves are opening and closing and they have correct clearance

have a look let me know engine model and spec number

cheers paul

Aug 26, 2010 | Husqvarna Garden

1 Answer

Fuel runs out the the right vent tube and breather hole when the engine is running. Disconnect the vac line from fuel tank and no leak. Is the vac fuel pump overpresuring the system? 1982 Suzuki GS750

The vacumn line only controls the flow from the fuel tap. When there is vacumn(motor running) the fuel will flow. It is not a pump and cannot pressurize the system. So when you remove the hose it effectively turns the fuel tap off.
If a carb is flooding , it is because the float valve is not sealing, either dirty, or it is damaged or worn. It is sometimes possible to stop it with a tap from the handle of a screwdriver etc on the carb bowl. but more than likely the carbs will need cleaning and servicing. and I have no idea why this answer is typing in italics

May 15, 2010 | Motorcycles

1 Answer

Took carb apart and clean then put back together with new gaskets. will not start without starter fluid and only for 2 secs then dies will not start on its on has new spark plug and gas line with fresh...

Lets back up and regroup on the carb work:

Hi and welcome to FixYa. I am Kelly.
This is how to clean the fuel passages in the carb.
Here is what you need to do:

1. Fuel selector off
2. Remove float bowl mounting screws and nut
3. Remove the BRASS Jet / Orifice in the very bottom of the venturi tube inside the pickup tube. (Flat blade screwdriver) Hold the Orifice up to the light. You should see a pinhole. If it is not clear clean the orifice but do not force anything through the hole.
4. Underneath the Orifice there is yet another BRASS tube that you need to remove. (Flat blade screwdriver) Make sure all of the holes in the tube are clear. The tube will be over 2 inches long. Clean it and reinstall it.
5. Reinstall the Orifice.
6. Using a catch fuel container turn on the fuel selector. Fuel should flow at a good rate. GENTLY lift the float assy level and make sure fuel flow shuts off. When you drop the float again fuel should flow.
If you do not have fuel flow at this point the needle and seat will need to be inspected. Fuel selector OFF.
(The following procedure is to be done only if there is no fuel flow with fuel selector on.)
a. Remove the silver float pivot pin retaining screw
b. Drop the Float down (The needle will come off with the float. NOTE the position)
c. Inspect the tapered rubber of the needle If should be pointed. If it is not pointed then the rubber tip is stuck inside the seat.
d. Clean the seat hole ONLY if obstructed. (Easily damaged)
e. FUEL Selector on then off fuel should rapidly flow through the needle seat.
f. Renistall Float and needle making sure to get the pivot / hinge pin installed correctly and reinstall the silver retaining screw.
g. Fuel selector ON. Raise and lower float checking for free movement and fuel flow.

7. If there still is no fuel flow at this point remove the fuel hose from the carb and check fuel flow. If no flow check that gas tank exit hole, fuel filter (if installed) and the selector valve assy for obstructions. Reassemble connections.


8. BEFORE you install the float bowl inspect the bowl nut. There are 2 holes in the side of the nut where it screws in to the bottom of the carb that must be clear.

9. Install Float bowl mounting screws and nut. Check for leaks.

10. Test engine.

That should do it. (carb cleaning 101)

Thanks for using FixYa.

P.S. If it still does not start and you have a primer bulb on the carb the primer bulb most likely has a hole in it. Press and hold the primer bulb CLOSED against the carb inner mating surfaces and see if it will start. (2 people required) If it starts and runs the primer bulb has a pin hole in it.

Apr 12, 2010 | Toro Lawn Mower With Toro Power Tools

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