8N Carburetor Question

dactura · Aug 3, 2015

[b:654c4848f0]Background:[/b:654c4848f0] Ran the '47 8N out of gas - filled it back up and then started to have problems getting it going: cranked a lot like it wasn't getting fuel. Took plug at bottom of carburetor out as the guru's suggest to demonstrate gas flows... indeed it did down my hand, arm and exit at the elbow. Put plug back in and went for a walk to thank it over. I removed a spark plug earlier to inspect for fouling... but it neat and pretty. I went for a walk and decided I should have tested for spark, so when I came back from the walk (about an hour) I removed the spark plug again and cranked it for spark. I got spark and it began to start. Elated, I put the plug back in and it started right up.

[b:654c4848f0]Question:[/b:654c4848f0] The plug in the bottom of the carburetor - do you suppose that drains all the crap from a dirty tank? My guess is that the low fuel allowed crap to flow into the carburetor and the plug is a feature of the carb that allows for easy cleaning. Can anyone confirm/explain the function of the drain plug?

R Geiger · Aug 3, 2015

Before the fuel gets to the plug it should go thru three screens, if you have them in place, so no the plug is not there to drain out the muck in the bottom of the tank.

When I pull the plug to check fuel flow, I first turn off the fuel, then remove plug and then open valve and catch the fuel in a pint jar. That way you can tell how good the flow is and you don't have fuel running down your arm. It should fill a pint jar in 2 minutes or so.

dactura · Aug 3, 2015

Hmmm. A pint! That's a lot of gas in the carb. I didn't have such expectations when I removed the plug (my first time) but the plug has been worn
down by previous mechanics who favored vise-grips to an end wrench... so removal was not fun and without precision. (Now I know the jar on my advanced
tech air cleaner will do double duty... Maybe that's what it's for - doesn't seem to catch much crud)

Where are the 3 screens? I think I remember cleaning the one in the gas tank and one in the fuel bowl? I do not know of a third.

R Geiger · Aug 3, 2015

(quoted from post at 01:07:30 08/04/15) Hmmm. A pint! That's a lot of gas in the carb. I didn't have such expectations when I removed the plug (my first time) but the plug has been worn
down by previous mechanics who favored vise-grips to an end wrench... so removal was not fun and without precision. (Now I know the jar on my advanced
tech air cleaner will do double duty... Maybe that's what it's for - doesn't seem to catch much crud)

Where are the 3 screens? I think I remember cleaning the one in the gas tank and one in the fuel bowl? I do not know of a third.

The third should be part of the brass elbow where the fuel line attaches to the carb.
Bt letting it fill a pint jar, you are verifying the fuel flow not just draining the carb bowl, When you first pull the plug, you get the fuel in the bowl and if you put the plug back in real quick, you do not find out if you have a fuel flow problem.

One of my 8n's had a plugged stand pipe on top of bowl assemby. It would run a bit and die, run a bit and die. screens all looked good tho. I ended up replacing the sediment bowl assy.

You could replace the plug in the bowl pretty easy. Ace hardware should have them.

Dalex · Aug 3, 2015

Generally there is a cone shaped screen in the elbow where it goes into the carb . Just blow it out...

dactura · Aug 3, 2015

Thanks! Your explaination is very helpful!

old · Aug 3, 2015

You may have a coil on it way out since you said waited an hour then tested for spark and an hour is about how long it takes for a coil; to heat up and start messing up

8N Carburetor Question

dactura

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R Geiger

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dactura

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R Geiger

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Dalex

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dactura

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old

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