Wierd
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Tuned
Joined: Feb 2022
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From: Central Montana
Wierd
I got a new 2 barrel carb on my 351w. And ever since it lopes a lot at low rpm to the point I'm worried it will doe and it's independent of temperature. I've also lost the ability to kick it into or out of high idle. Honestly just hoping for a good guide on carb tune touch up if nothing else
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From: Virginia
Get it completely warmed up. That probably means driving it a few miles and then coming back home. Take the aircleaner off and get it started and idling again.
On the top of the carb there is a large metal door(called the choke). When it's completely warmed up, that door should be straight up and down. If it's not, you can loosen the 3 screws that hold the round black cap on the pass side of the carb, and grab the black cap and turn it. One way you turn it will make the door try to shut, the other way will make it open. Turn the cap till the door is straight up and down, then tighten the 3 screws back down. Then goose the throttle and see if the idle lowers down.
If the idle goes down after the choke adjustment, if it is idling too slow, the first thing I would do is adjust the idle mixture screws. These are two screws on the front of the carb, underneath the square part of the carb. Look under there to find them. They will be two screws with springs on them. With it idling slow, turn one screw in. If it speeds up good, go to the other screw and do the same. If the engine slows when you turn the screw in, then turn it out. Keep turning it out till the engine runs the fastest and smoothest. Then go to the other screw and do the same. Then go back to the first screw and turn it in till engine just starts to slow, then turn it out till it runs the fastest, then 1/4 turn more. Do the same with the 2nd screw.
After adjusting the mixture screws, the engine may be idling too fast or the same that it was, which I think you said was too slow. If the idle is too fast or too slow, there is a screw on the driver's side where the throttle is located. You should be able to turn that screw and adjust the idle speed.
There are several other things that can happen that might need to be addressed. If you need to write back in and we will tackle those if they come up.
On the top of the carb there is a large metal door(called the choke). When it's completely warmed up, that door should be straight up and down. If it's not, you can loosen the 3 screws that hold the round black cap on the pass side of the carb, and grab the black cap and turn it. One way you turn it will make the door try to shut, the other way will make it open. Turn the cap till the door is straight up and down, then tighten the 3 screws back down. Then goose the throttle and see if the idle lowers down.
If the idle goes down after the choke adjustment, if it is idling too slow, the first thing I would do is adjust the idle mixture screws. These are two screws on the front of the carb, underneath the square part of the carb. Look under there to find them. They will be two screws with springs on them. With it idling slow, turn one screw in. If it speeds up good, go to the other screw and do the same. If the engine slows when you turn the screw in, then turn it out. Keep turning it out till the engine runs the fastest and smoothest. Then go to the other screw and do the same. Then go back to the first screw and turn it in till engine just starts to slow, then turn it out till it runs the fastest, then 1/4 turn more. Do the same with the 2nd screw.
After adjusting the mixture screws, the engine may be idling too fast or the same that it was, which I think you said was too slow. If the idle is too fast or too slow, there is a screw on the driver's side where the throttle is located. You should be able to turn that screw and adjust the idle speed.
There are several other things that can happen that might need to be addressed. If you need to write back in and we will tackle those if they come up.
FTE Legend
Joined: Nov 2015
Posts: 30,935
Likes: 4,124
From: Angier, NC
I would say what Dave posted is good, did not rear ti fully, but before you get started and the motor heated up I would pull the air filter off and check the choke to make sure it is closed.
You will need to move the throttle for it to close.
If it dose not then I would adjust it so it dose.
Then do as Dave posted.
Dave ----
You will need to move the throttle for it to close.
If it dose not then I would adjust it so it dose.
Then do as Dave posted.
Dave ----
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Tuned
Joined: Feb 2022
Posts: 295
Likes: 7
From: Central Montana
I would say what Dave posted is good, did not rear ti fully, but before you get started and the motor heated up I would pull the air filter off and check the choke to make sure it is closed.
You will need to move the throttle for it to close.
If it dose not then I would adjust it so it dose.
Then do as Dave posted.
Dave ----
You will need to move the throttle for it to close.
If it dose not then I would adjust it so it dose.
Then do as Dave posted.
Dave ----
Thread Starter
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Tuned
Joined: Feb 2022
Posts: 295
Likes: 7
From: Central Montana
I would say what Dave posted is good, did not rear ti fully, but before you get started and the motor heated up I would pull the air filter off and check the choke to make sure it is closed.
You will need to move the throttle for it to close.
If it dose not then I would adjust it so it dose.
Then do as Dave posted.
Dave ----
You will need to move the throttle for it to close.
If it dose not then I would adjust it so it dose.
Then do as Dave posted.
Dave ----
Get it completely warmed up. That probably means driving it a few miles and then coming back home. Take the aircleaner off and get it started and idling again.
On the top of the carb there is a large metal door(called the choke). When it's completely warmed up, that door should be straight up and down. If it's not, you can loosen the 3 screws that hold the round black cap on the pass side of the carb, and grab the black cap and turn it. One way you turn it will make the door try to shut, the other way will make it open. Turn the cap till the door is straight up and down, then tighten the 3 screws back down. Then goose the throttle and see if the idle lowers down.
If the idle goes down after the choke adjustment, if it is idling too slow, the first thing I would do is adjust the idle mixture screws. These are two screws on the front of the carb, underneath the square part of the carb. Look under there to find them. They will be two screws with springs on them. With it idling slow, turn one screw in. If it speeds up good, go to the other screw and do the same. If the engine slows when you turn the screw in, then turn it out. Keep turning it out till the engine runs the fastest and smoothest. Then go to the other screw and do the same. Then go back to the first screw and turn it in till engine just starts to slow, then turn it out till it runs the fastest, then 1/4 turn more. Do the same with the 2nd screw.
After adjusting the mixture screws, the engine may be idling too fast or the same that it was, which I think you said was too slow. If the idle is too fast or too slow, there is a screw on the driver's side where the throttle is located. You should be able to turn that screw and adjust the idle speed.
There are several other things that can happen that might need to be addressed. If you need to write back in and we will tackle those if they come up.
On the top of the carb there is a large metal door(called the choke). When it's completely warmed up, that door should be straight up and down. If it's not, you can loosen the 3 screws that hold the round black cap on the pass side of the carb, and grab the black cap and turn it. One way you turn it will make the door try to shut, the other way will make it open. Turn the cap till the door is straight up and down, then tighten the 3 screws back down. Then goose the throttle and see if the idle lowers down.
If the idle goes down after the choke adjustment, if it is idling too slow, the first thing I would do is adjust the idle mixture screws. These are two screws on the front of the carb, underneath the square part of the carb. Look under there to find them. They will be two screws with springs on them. With it idling slow, turn one screw in. If it speeds up good, go to the other screw and do the same. If the engine slows when you turn the screw in, then turn it out. Keep turning it out till the engine runs the fastest and smoothest. Then go to the other screw and do the same. Then go back to the first screw and turn it in till engine just starts to slow, then turn it out till it runs the fastest, then 1/4 turn more. Do the same with the 2nd screw.
After adjusting the mixture screws, the engine may be idling too fast or the same that it was, which I think you said was too slow. If the idle is too fast or too slow, there is a screw on the driver's side where the throttle is located. You should be able to turn that screw and adjust the idle speed.
There are several other things that can happen that might need to be addressed. If you need to write back in and we will tackle those if they come up.
Lead Driver
Joined: Apr 2002
Posts: 5,338
Likes: 1,248
I agree with the two Daves. The only thing I'd add is if this is not a new carburetor or rebuilt and it's been run with ethanol fuel I would first turn in the idle screws gently till they seat there by reaming and cleaning the orafice. Count the number of turns in and then back them out the same number of turns. This one trick alone can solve many idling issues. But if it doesn't proceed as directed by the Daves.
Thread Starter
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Tuned
Joined: Feb 2022
Posts: 295
Likes: 7
From: Central Montana
Get it completely warmed up. That probably means driving it a few miles and then coming back home. Take the aircleaner off and get it started and idling again.
On the top of the carb there is a large metal door(called the choke). When it's completely warmed up, that door should be straight up and down. If it's not, you can loosen the 3 screws that hold the round black cap on the pass side of the carb, and grab the black cap and turn it. One way you turn it will make the door try to shut, the other way will make it open. Turn the cap till the door is straight up and down, then tighten the 3 screws back down. Then goose the throttle and see if the idle lowers down.
If the idle goes down after the choke adjustment, if it is idling too slow, the first thing I would do is adjust the idle mixture screws. These are two screws on the front of the carb, underneath the square part of the carb. Look under there to find them. They will be two screws with springs on them. With it idling slow, turn one screw in. If it speeds up good, go to the other screw and do the same. If the engine slows when you turn the screw in, then turn it out. Keep turning it out till the engine runs the fastest and smoothest. Then go to the other screw and do the same. Then go back to the first screw and turn it in till engine just starts to slow, then turn it out till it runs the fastest, then 1/4 turn more. Do the same with the 2nd screw.
After adjusting the mixture screws, the engine may be idling too fast or the same that it was, which I think you said was too slow. If the idle is too fast or too slow, there is a screw on the driver's side where the throttle is located. You should be able to turn that screw and adjust the idle speed.
There are several other things that can happen that might need to be addressed. If you need to write back in and we will tackle those if they come up.
On the top of the carb there is a large metal door(called the choke). When it's completely warmed up, that door should be straight up and down. If it's not, you can loosen the 3 screws that hold the round black cap on the pass side of the carb, and grab the black cap and turn it. One way you turn it will make the door try to shut, the other way will make it open. Turn the cap till the door is straight up and down, then tighten the 3 screws back down. Then goose the throttle and see if the idle lowers down.
If the idle goes down after the choke adjustment, if it is idling too slow, the first thing I would do is adjust the idle mixture screws. These are two screws on the front of the carb, underneath the square part of the carb. Look under there to find them. They will be two screws with springs on them. With it idling slow, turn one screw in. If it speeds up good, go to the other screw and do the same. If the engine slows when you turn the screw in, then turn it out. Keep turning it out till the engine runs the fastest and smoothest. Then go to the other screw and do the same. Then go back to the first screw and turn it in till engine just starts to slow, then turn it out till it runs the fastest, then 1/4 turn more. Do the same with the 2nd screw.
After adjusting the mixture screws, the engine may be idling too fast or the same that it was, which I think you said was too slow. If the idle is too fast or too slow, there is a screw on the driver's side where the throttle is located. You should be able to turn that screw and adjust the idle speed.
There are several other things that can happen that might need to be addressed. If you need to write back in and we will tackle those if they come up.
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Tuned
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From: Virginia
If the choke door is closed when cold in the morning, and opens up straight when it's warmed up, don't mess with it. Why can't you adjust the idle mixture and the idle speed screws?
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Tuned
Joined: Feb 2022
Posts: 295
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From: Central Montana
It completely blanked on me to do that
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Tuned
Joined: Feb 2022
Posts: 295
Likes: 7
From: Central Montana
Dropped the high idle since I can't get it out of that
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