another carb question

June 13, 2022, 07:28 AM

Curly1

I do not think it is a lean idle issue. The hose on top in the picture above is good to have and may resolve part of the issue. Is it doing it when you let off on the gas or when you hit brakes hard? (could be sloshing fuel from vent tubes)

First I would start by doing what everyone needs to be doing to carb every other race or so. Blow out all of the bleed jets on top of carb with carb cleaner until you can see or hear that they are open. A carb will act goofy if they are clogged and they get clogged easily.

If it runs good until you let off then you may have a fuel supply issue. If you have a deadhead regulator remove it and throw it away or give it to someone you really do not like. You could make a pass and kill ignition and fuel pump immediately and then check float level and see where it is at.
Gas or Alcohol? Makes a difference on how we troubleshoot it.
If it is alcohol what needle and seats?
What fuel pump?
What fuel pressure?

With the limited information you gave us hard to diagnose but I would start with fuel sloshing if it is doing it under hard braking or float level when it does it.

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June 13, 2022, 07:41 AM

CURTIS REED

Did it just start doing it or has it always done it since you put it on?

June 13, 2022, 09:29 AM

TOP38

quote:
Originally posted by camaro77:
I have a 1050 dominator that runs great but once I let off after the pass it wants to just die out is this a lean idle issue. thinking richen up the idle circuit some may help any thoughts?

Likely it's too rich from fuel slosh due to braking,,, easy to tell if this is the case, when you lift early in a run and don't brake hard and it doesn't do it... Adding extensions to the vent tubes is NOT the fix as fuel is not coming out of the bowl vents. Hard braking forces fuel from the primary side to ram into the jets and cause excess fuel to flow out the boosters. Another tell tail is if you pop it in neutral and give it throttle to keep it from stalling.

It this is the case your float level could be on the high side.

June 13, 2022, 10:57 AM

Curly1

quote:
Originally posted by TOP38:
quote:
Originally posted by camaro77:
I have a 1050 dominator that runs great but once I let off after the pass it wants to just die out is this a lean idle issue. thinking richen up the idle circuit some may help any thoughts?

Likely it's too rich from fuel slosh due to braking,,, easy to tell if this is the case, when you lift early in a run and don't brake hard and it doesn't do it... Adding extensions to the vent tubes is NOT the fix as fuel is not coming out of the bowl vents. Hard braking forces fuel from the primary side to ram into the jets and cause excess fuel to flow out the boosters. Another tell tail is if you pop it in neutral and give it throttle to keep it from stalling.

It this is the case your float level could be on the high side.

That was my thoughts and that is why I asked a few questions to narrow it down more.

A simple thing is to just change carb with another known good one to make sure it is in carb before going too far. If it does it with different carb look at fuel supply. If it cures it then possibly the whistle? inside has been removed, float level too high, fuel pressure too high. Just need more information, carbs are really simple overall.

June 13, 2022, 04:47 PM

Goob

One or both idle stops are too high, you're pulling fuel through the intermediate circuit.
Put it in neutral as mentioned and see if that cleans it up some.

June 13, 2022, 09:32 PM

camaro77

quote:
Originally posted by Mike Rietow:
Carb look like this? Except what?

yes I have the hose

June 13, 2022, 09:42 PM

camaro77

quote:
Originally posted by Curly1:
I do not think it is a lean idle issue. The hose on top in the picture above is good to have and may resolve part of the issue. Is it doing it when you let off on the gas or when you hit brakes hard? (could be sloshing fuel from vent tubes)

First I would start by doing what everyone needs to be doing to carb every other race or so. Blow out all of the bleed jets on top of carb with carb cleaner until you can see or hear that they are open. A carb will act goofy if they are clogged and they get clogged easily.

If it runs good until you let off then you may have a fuel supply issue. If you have a deadhead regulator remove it and throw it away or give it to someone you really do not like. You could make a pass and kill ignition and fuel pump immediately and then check float level and see where it is at.
Gas or Alcohol? Makes a difference on how we troubleshoot it.
If it is alcohol what needle and seats?
What fuel pump?
What fuel pressure?

With the limited information you gave us hard to diagnose but I would start with fuel sloshing if it is doing it under hard braking or float level when it does it.

carb is clean
fuel pump is magna fuel 500 set at 18 lbs
regulated to 6lbs at carb
running on gas
has done it all last yr but i just delt with it
I do get on the brakes pretty hard
I do shut it down and its a real bear to get restarted on the return road which I guess could be a rich condition

June 14, 2022, 07:18 AM

Curly1

Are you sure the floats are good? When you have a bad float you adjust your needle and seat to get float level back up but it limits how much the needle opens.

I have never done this before but I think I would kill the motor and fuel pump as soon as you cross the line then check float levels. If it is low look for possible bad floats. I would also take float bowls off and flip them over and see where the floats are set. It probably should be around 3/8 inch gap at top upside down. If it is down much more than that bad float.

Do you know what needles and seats you have in there?

Your fuel pump and fuel pressure sounds good but that does not mean it is getting past the needle and seats. Do you know if that carb has the white plastic slosh whistles inside?

Those are a few things to check. Also I would change out carb with a known good carb to try just make sure it is carb. Although unlikely I have seen weird electrical problem with broken wire or bad connection under acceleration or stopping.
I really think it is a carb issue but since it is so easy to change it out I would try another just to make sure. Hope this helps narrow it down.

June 14, 2022, 10:23 AM

CURTIS REED

quote:
Originally posted by camaro77:

carb is clean
fuel pump is magna fuel 500 set at 18 lbs
regulated to 6lbs at carb
running on gas
has done it all last yr but i just delt with it
I do get on the brakes pretty hard
I do shut it down and its a real bear to get restarted on the return road which I guess could be a rich condition

It's quite possible that if you are high on float level when you slam the throttle shut they are getting a large shot of fuel then trying to shut and do their job. Also with high float levels you get fuel slosh making it go way rich from both. I'm not talking about fuel out of the vents. JMO

June 14, 2022, 12:20 PM

camaro77

I have a brand new TMC twin blade I will be trying hopefully soon

June 14, 2022, 12:50 PM

Wooley

One question no one has touched on yet. I ask based on the answer that you gave saying this has been an issue for a while now. Where is the fuel cell mounted,and how high is it in relation to the carburetor? I ask based on a problem I had and was finally able to solve on my old car.

June 14, 2022, 01:42 PM

camaro77

front mounted cell tube chassis car and its mounted to the main frame rails

June 14, 2022, 01:51 PM

Wooley

Is the cell in the front or the back. If in back how high is the bottom of the cell in relation to the carburetor? Is it near the same height? Is the top of the cell above the carburetor? I’m looking for where the fuel level in relation to the carburetor

June 14, 2022, 02:12 PM

Wooley

quote:
Originally posted by Wooley:
Is the cell in the front or the back. If in back how high is the bottom of the cell in relation to the carburetor? Is it near the same height? Is the top of the cell above the carburetor? I’m looking for where the fuel level is in relation to the carburetor

June 14, 2022, 02:13 PM

Wooley

Sorry for double post.

June 14, 2022, 05:35 PM

rusty

quote:
One or both idle stops are too high, you're pulling fuel through the intermediate circuit.
Put it in neutral as mentioned and see if that cleans it up some.

x2,close the butterflies and open them equally,adjust fuel ratio for idle speed,or possibily a hole in the blade for air