I should have never made the last post. This morning the flooding returned. I also filled the tank - coincidence?
Flooding 2150
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
You mentioned having to use a dremmel to fit the air horn onto the main body? This carb sounds like bad news to begin with. If you had to cut away a piece of the air horn to get it to lie flat on the carb, that is a red flag. Could you elaborate on this a bit?
Have you tried idling the motor with the air horn off to watch the fuel level to make sure that the problem isn't on the fuel-bowl side of the carb? If that part checks out fine...then perhaps the booster venturis weren't seated all the way somehow...and them not being seated wouldn't let the air horn itself seat. I'm just saying the fact you had to physically cut the carb to get it to go together is a big sign of something. However I don't have an explanation for why it takes a while to flood...the boiling over explanation makes more sense there.
Have you tried idling the motor with the air horn off to watch the fuel level to make sure that the problem isn't on the fuel-bowl side of the carb? If that part checks out fine...then perhaps the booster venturis weren't seated all the way somehow...and them not being seated wouldn't let the air horn itself seat. I'm just saying the fact you had to physically cut the carb to get it to go together is a big sign of something. However I don't have an explanation for why it takes a while to flood...the boiling over explanation makes more sense there.
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Senior User
Joined: Apr 2004
Posts: 289
Likes: 1
From: Raleigh, NC
The part that had to be filed down was, when looking at the bottom of the air horn, a semi-circular raised portion around the hole for the air filter stud. This hit the main carb casting before anything else and I can only imagine there's another casting out there that allows this to clear. We're not talking about much here but a 32nd of an inch of material - enough to allow air at the back of the carb. I don't believe there was any real performance issue associated with this. I have not run the motor with the air horn off. I will do that this evening. Yesterday, when the flooding occurred, I saw gas coming directly from the booster venturis after the motor was turned off. I am also going to try and reseat the ball and weight because I have no other assembly related items to cause the problem. This carb has the factory aluminum spacer and the carb is so hot I can't hold it. I know that isn't very hot in motor terms and the engine runs relatively cool but I'm also wondering if the booster pump has the fuel heated enough to open the valve. Or if the valve is opening because of the heat, wouldn't the fuel siphon into the carb?
Last edited by RaleighDad66; Aug 17, 2004 at 03:25 PM.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Ah, so you just had to flatten it out to get a seal. No big deal at all.
Definitely do the fuel level check...perhaps check over the accelerator pump too (umbrella check valve, diaphragm pointing the right way, spring, ball and weight). Maybe something is sticking and you're getting constant fuel through the discharge passage. I can't think up a way for it to happen at the moment but sounds like you're scraping the bottom of the barrel now so I'm just throwing things out there.
Definitely do the fuel level check...perhaps check over the accelerator pump too (umbrella check valve, diaphragm pointing the right way, spring, ball and weight). Maybe something is sticking and you're getting constant fuel through the discharge passage. I can't think up a way for it to happen at the moment but sounds like you're scraping the bottom of the barrel now so I'm just throwing things out there.
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Senior User
Joined: Apr 2004
Posts: 289
Likes: 1
From: Raleigh, NC
Yesterday, with the air horn off, I ran the motor for an hour and the fuel level rises in the bowl but does not overflow yet, when very hot, the fuel appears to siphon into the booster venturi. Strangely enough, the fuel level, at the correct float adjustment, is the same height as the mounting base of the venturi assembly. I adjusted the float level down to 3/4 inch (chart says 7/16 inch) and I also restricted the fuel flow by pinching the rubber hose from the fuel pump to the carb. This is a new fuel pump so I am trusting it's got the correct pressure. I made my trip this morning and had no problems. I will know more after my long, hot drive home this evening. I will then remove the vice grip from the fuel line and repeat. If this is all caused by an over zealous fuel pump I will scream.
That was several days ago.. Now I have had the clamp removed from the fuel line for three days and everything seems normal. I may run into problems with long, hard acceleration but the flooding appears to be gone (knock on wood). Something must still be goofy because of the need for the low fuel level adjustment required to make things work. We have also had several moderate days under 85 degrees F so we'll see if the additional heat plays into the picture.
That was several days ago.. Now I have had the clamp removed from the fuel line for three days and everything seems normal. I may run into problems with long, hard acceleration but the flooding appears to be gone (knock on wood). Something must still be goofy because of the need for the low fuel level adjustment required to make things work. We have also had several moderate days under 85 degrees F so we'll see if the additional heat plays into the picture.
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Senior User
Joined: Apr 2004
Posts: 289
Likes: 1
From: Raleigh, NC
Mechanical. What would be the best way of measuring that pressure? My gauges are not sensitive enough.
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From: MCBH Kaneohe Bay, HI
Did ya make sure that the float pivot pin has a C shaped clip on it and that the clip is properly snapped onto the seat? Also, are you sure that the needle valve is the same shape as the sealing surface on the seat? The rubber on the end of the needle valve should be there. Also that the float doesn't have some kind of pin hole in it which would fill up with gas when it gets hot?
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Senior User
Joined: Apr 2004
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From: Raleigh, NC
All components are installed. The float is new and as a bench test I would blow into the fuel inlet and raise and lower the float to determine the seating position relative to the float position. The needle valve and the seat are also new. I have the clip installed to keep the float retained to the seat and the clip to keep the needle to the float is also being used. A new month is coming and this carb and post has lived too long. Something this flaky is always explanable but sometimes it's best to not put forth the effort to determine the cause. Sometimes I have to tell the kids "Because I said so!"
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
I know you're about fed up, but is blowing into the inlet the main way you've been adjusting the float? Seems like it'd be hard to get an accurate measurement that way.
Also I really like redneckdieselmechanic's thought about the float soaking up gas...didn't think about it. Try a new float; they're cheap. I believe it is rare for this to happen but it's worth a shot before you buy a new carb.
Also I really like redneckdieselmechanic's thought about the float soaking up gas...didn't think about it. Try a new float; they're cheap. I believe it is rare for this to happen but it's worth a shot before you buy a new carb.
Last edited by fmc400; Aug 30, 2004 at 08:31 AM.
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