Briggs 422707 opposed twin carb

[McTurff]

Im finish up a long battle with this machine and maybe at the finish line.
After many months of trial and error I found my problem !!
This motor had a 3 screw carb which i haven't been able to get right so will keep working on it in the mean time put a 4 screw carb on and it runs but not perfect! Take air box off and it runs pretty dang good and after looking at the air box it had one hole for vent or jet to the 3 screw carb which only had one hole on top! so the other hole was being blocked for the 4 screw carb!
So probably obvious question should I drill out the other hole??
Has anyone experienced this situation!
Here are some pics
Carb no gasket with gasket and the air cleaner base!
Thanks

 

[Skippydiesel]

I don't know your engine/carburettor

Sounds like the engine is running rich, when you attach the airbox .

I think you may have hit the nail on the head - "the other hole was being blocked for the 4 screw carb!"

You may be inadvertently restricting airflow/atmospheric pressure to the carby. Drilling may be the way to go. My concern would be the potential to let unfiltered air into the carby.

 

[McTurff]

I don't know your engine/carburettor

Sounds like the engine is running rich, when you attach the airbox .

I think you may have hit the nail on the head - "the other hole was being blocked for the 4 screw carb!"

You may be inadvertently restricting airflow/atmospheric pressure to the carby. Drilling may be the way to go. My concern would be the potential to let unfiltered air into the carby.

The air is filtered as it is inside air cleaner !
Thanks

 

[Tiger Small Engine]

Im finish up a long battle with this machine and maybe at the finish line.
After many months of trial and error I found my problem !!
This motor had a 3 screw carb which i haven't been able to get right so will keep working on it in the mean time put a 4 screw carb on and it runs but not perfect! Take air box off and it runs pretty dang good and after looking at the air box it had one hole for vent or jet to the 3 screw carb which only had one hole on top! so the other hole was being blocked for the 4 screw carb!
So probably obvious question should I drill out the other hole??
Has anyone experienced this situation!
Here are some pics
Carb no gasket with gasket and the air cleaner base!
Thanks

Briggs opposed twin, not exposed twin. I am familiar with these engines and carburetors. These carburetors have the fuel pump built into the carburetor. Obviously, your air/fuel mixture is pretty close, but not correct. If start drilling out a hole, you better start small. Where exactly would you be drilling out this new hole?

 

[ILENGINE]

Briggs opposed twin, not exposed twin. I am familiar with these engines and carburetors. These carburetors have the fuel pump built into the carburetor. Obviously, your air/fuel mixture is pretty close, but not correct. If start drilling out a hole, you better start small. Where exactly would you be drilling out this new hole?

The air cleaner base doesn't have a vent hole that corresponds with the bottom center left vent hole on the carb. I think that is were he is considering drilling the hole in the air cleaner base to line up with that hole in the carb.

 

[Auto Doc's]

Hello C.,

What does to top of the original carburetor, where the air cleaner mounts look like? The 3 larger holes on top are threaded to mount the air cleaner base. The small hole is just a fuel bowl vent. That hole should always be open and line up with the top of the carburetor vent.

From your description this sounds more like a mixture adjustment problem.

I was under the impression that the "3 screw" versus "4 screw" had to do more with the carburetor fuel pulse pump than the top of the carburetor. It's been a while since I have dealt with this style.

There is a mixture adjustment screw on the base of the carburetor directly below the pulse pump. Have you tried any adjustment to that screw?

The mixture should be adjusted with the air cleaner in place to compensate for the air cleaner element air drag. Also, the air cleaner and foam prefilter need to be kept clean.

 

[Douglas Lee]

McTurff,
Just curious, what make is the carburetor?
Thanks . . .
*

 

[McTurff]

Briggs opposed twin, not exposed twin. I am familiar with these engines and carburetors. These carburetors have the fuel pump built into the carburetor. Obviously, your air/fuel mixture is pretty close, but not correct. If start drilling out a hole, you better start small. Where exactly would you be drilling out this new hole?

Briggs opposed twin, not exposed twin. I am familiar with these engines and carburetors. These carburetors have the fuel pump built into the carburetor. Obviously, your air/fuel mixture is pretty close, but not correct. If start drilling out a hole, you better start small. Where exactly would you be drilling out this new hole?

 

[McTurff]

The yellow dot not perfect but you can see to correspond with the gasket and carb

 

[McTurff]

McTurff,
Just curious, what make is the carburetor?
Thanks . . .
*

No names on carbs
New one is Chinese I have 3
Two 4 screw and one 3 screw!
I also have a new engine i am getting today but don't know what carb is on that one!
But the one im using works fine but not with air box so wondering if others have done the same?
You can see pic
One on right is the 3 screw carb with one corresponding hole which matches air cleaner!
Holes are the ones at bottom of carb in pic!!