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Daryl G
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876 Posts
Discussion Starter #1
I am having a fuel delivery problem on one of my machines. When attempting to start the machine I have to use brake cleaner and it runs for a few cycles (until the brake cleaner is consumed) and shows no attempt to crank without using this elixir! The fuel tank is full and no fuel comes out after removing the pipe plug at the bottom of the carburetor. After removing the fuel line and replacing it on the nipple, fuel does start running from the carburetor drain hole. The fuel lines are clear and the fuel filter is in nice shape. The best I can guess is that the carburetor vent is clogged; however, I have NO idea where the vent is located. Can anyone tell me where the carburetor vent is located?

Surprisingly, once the carburetor is full the machine runs fine for an hour or so then the engine stops like it was starved of fuel. I have to repeat the removal of the fuel line procedure again in order for fuel to finally emerge from the carburetor drain hole.
 

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Just like in plumbing it has to have a vent.
Would it be the same as the mixing vent or valve? I mean a carb is a fuel/air mixing devise and of course delivery to wich is done by suction I recon.
But I agree you need air.
I ordered one of those shiney gas caps and was wondering about the air vent hole to and could drill a small one in it myself or go to auto parts store and see if I can get a vented cap to fit.
Good luck Buddy
 

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I am having a fuel delivery problem on one of my machines. When attempting to start the machine I have to use brake cleaner and it runs for a few cycles (until the brake cleaner is consumed) and shows no attempt to crank without using this elixir! The fuel tank is full and no fuel comes out after removing the pipe plug at the bottom of the carburetor. After removing the fuel line and replacing it on the nipple, fuel does start running from the carburetor drain hole. The fuel lines are clear and the fuel filter is in nice shape. The best I can guess is that the carburetor vent is clogged; however, I have NO idea where the vent is located. Can anyone tell me where the carburetor vent is located?

Surprisingly, once the carburetor is full the machine runs fine for an hour or so then the engine stops like it was starved of fuel. I have to repeat the removal of the fuel line procedure again in order for fuel to finally emerge from the carburetor drain hole.
This may sound dumb but is your air filter assy closed up to tight? Like the top screw on cover so it cant breath very well?
 

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Have you determined that the float needle isn't sticking?

It's possible that your cap is so tight, with no vent, that it's causing a flow problem, but I can't believe that would be an issue after the machine has been sitting. The easy way to tell if that's the problem is

1. get it into the no-fuel-delivery state
2. remove the cap
3. see if fuel starts flowing

I don't buy the clogged-vent-in-the-carb theory. There are too many openings into the bowl. But it does sound like the float needle might be sticky. The act of fiddling with the carb could provide enough disturbance to knock it loose. It doesn't take much to make that thing move (or not move).
 

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Daryl G
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876 Posts
Discussion Starter #6
I'm thinking the gas cap vent, try running it with the cap off or on but loose
I had the gas cap off during my attempts to crank so this, although plausible, is not my source of the problem (I had a similar issues years ago and that one was hard to chase as it WAS the lack of ventilation through the gas cap!).

Have you determined that the float needle isn't sticking?

It's possible that your cap is so tight, with no vent, that it's causing a flow problem, but I can't believe that would be an issue after the machine has been sitting. The easy way to tell if that's the problem is

1. get it into the no-fuel-delivery state
2. remove the cap
3. see if fuel starts flowing

I don't buy the clogged-vent-in-the-carb theory. There are too many openings into the bowl. But it does sound like the float needle might be sticky. The act of fiddling with the carb could provide enough disturbance to knock it loose. It doesn't take much to make that thing move (or not move).
jrd,
Hmmm... the clogged-vent-in-the-carb theory came to me after conducting a very sophisticated test - I removed the fuel line connection from the tank while leaving the other end connected to the carburetor, wiped the end really well, and attempted to blow into the carburetor, hard... no air would pass (I would have included this test yesterday in my original post but it was so backwoods of an idea, and probably not the wisest thing to go, but it does indicate that there is a venting problem in the carburetor - the fuel line was eliminated as I know it is clear). I will try to pull the bowl to see the condition of the float needle.
 

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Daryl G
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876 Posts
Discussion Starter #7
Just like in plumbing it has to have a vent.
Would it be the same as the mixing vent or valve? I mean a carb is a fuel/air mixing devise and of course delivery to wich is done by suction I recon.
But I agree you need air.
I ordered one of those shiney gas caps and was wondering about the air vent hole to and could drill a small one in it myself or go to auto parts store and see if I can get a vented cap to fit.
Good luck Buddy
Gerrard,
I also have one of those shiny gas caps that the automotive sells and I bet my was cheaper than yours!!!

I am glad you posted since that reminded me of something I have been meaning to ask you - do you still have that 0.030 over piston? I may have a need for one in the very near future (I am planning on taking an old jug of mine to the machine shop to see if this can be salvaged). Let me know if you are willing to part with it.
 

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Rubber tipped float needles can sometimes stick closed. All metal needles tend to leak by. As suggested, I would check the needle and seat.

The bowel vent passages are included in the castings for the carb body. Pretty tough to get it plugged. You can, however, block the vent if the gasket is the wrong one or out of place.
 

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Gerrard,
I also have one of those shiny gas caps that the automotive sells and I bet my was cheaper than yours!!!

I am glad you posted since that reminded me of something I have been meaning to ask you - do you still have that 0.030 over piston? I may have a need for one in the very near future (I am planning on taking an old jug of mine to the machine shop to see if this can be salvaged). Let me know if you are willing to part with it.
Actually I sold it to someone....I think anyway. Sorry Buddy
 

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3,028 Posts
Next time it starts to starve itself, tap the side of the carb with a screwdriver handle. If it takes off again then replace the fuel inlet jet and needle.

Roger,
 

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......Surprisingly, once the carburetor is full the machine runs fine for an hour or so then the engine stops like it was starved of fuel. I have to repeat the removal of the fuel line procedure again in order for fuel to finally emerge from the carburetor drain hole.
Doesn't surprise me a bit.

Sounds like fuel cap vent clogged.
Next time you run it, loosen the gas cap 30-45 minutes into your use.
loosen the cap for a couple seconds.
See if it goes another hour or just 15 minutes or so.
If it lasts another hour, it's the cap.
 

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If providing tank venting doesn't solve the problem, the first, I'd disconnect the fuel line and let it drain into a container. If the fuel runs out in a stream, not just drips, and continues until the tank is empty, then the issue is somewhere "down the line".

Check for a dirty in line fuel filter, or old gas line that might be swelled or collapsing. If it is old line, suggest replace all of it. Cheap to buy at an auto parts store.

If it has a fuel pump, you need to test that flow too. Frankly, small cost of replacing a fuel pump is probably worth it if that is an original or is old.

If fuel still flows well into the carb, then the problem is inside the carb. If it originally had a dry bowl when you first checked, I'd say maybe you have a faulty or sticking needle valve or a clogged passage somewhere internally. Disassembly and a good cleaning will likely solve the issue.

Just some thoughts on what could be wrong. Good luck finding out what is wrong with your particular machine.
 
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