Walbro vs Briggs logo carb settings

Are there differences in settings for the older Walbro vs the newer Briggs logo carb? I have the Briggs carb set at .900, needle 2nd from top, idle screw set for highest RPM at 2500 or so. We typically have an air density of about 90% (hot and humid). Should the float go higher than this on the Briggs carb to lean out the top end even more?
 

Kart43

Member
I have not heard that the fuel level is adjust according to carb body manufacturers. You have your float at .900" that is a setting which causes the fuel level to be low in the bowl, which is toward the leaner side, if you change the float height to .880 this causes the fuel level to be higher and causes a richer mixture. Are you confusing. Float height setting and fuel level?
 

CarlsonMotorsports

Premium User
Short answer = Yes.
The air circuit is different between the two carbs so they will be tuned differently.
You can go about tuning several ways on these carbs as you are well aware. Float height is just one of those methods.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
30 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
Thanks Brian. What are the differences please? Is it just a different air bleed setting or is everything different? I am going to try to use a wideband O2 sensor to fine tune our carb settings (Blue slide/sprint/typical air density is 90%) but want to be as close as possible when I start to save time.
 

Kart43

Member
Short answer = Yes.
The air circuit is different between the two carbs so they will be tuned differently.
You can go about tuning several ways on these carbs as you are well aware. Float height is just one of those methods.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
30 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
When you say the air circuit, are you referring to the low speed idle circuit, or the bleed to the emulsion tube? There are multiple air circuits.
 

Kimball

New member
When you say the air circuit, are you referring to the low speed idle circuit, or the bleed to the emulsion tube? There are multiple air circuits.
I have an older Walbro carb that I couldn't quite get dialed in so I'm curious too about how the idle air bleed is different. Can I assume the needle and float will be adjusted similar to a Briggs Carb.
 

CarlsonMotorsports

Premium User
When you say the air circuit, are you referring to the low speed idle circuit, or the bleed to the emulsion tube? There are multiple air circuits.
Both. Measure the passages.
I'd be curious to see a difference/measurement in volume. It is larger on all of the Chinese carbs.

The tune on the two bodies of carb is different.
I have a notebook full of notes on the tune on customers' Walbro carbs and it became just about worthless when the new carb was introduced. The new carbs are just fine, but they are different, and require a bit different tune (float height, air bleed setting, etc.)
 

Jimbo

If you talk the talk you should walk the walk
I haven't found that tuning them is different and have multiple major series champions.
The main circuit air bleed tube has a different size entrance but the calibrated hole is the same size it always has been.
Briggs spent a lot of time and money developing their carb to be the same as the Walbro.
The old version carbs are not any better or worse than the new ones!!
 

jjchat

Member
The air bleed on a Walboro tends to want 2+ turns out (near sea level) while the Briggs carb is about 1 turn. Once they are both set, I am not seeing a consistent difference on the DYno. I have not seen much of a difference between the float and needle settings between the two. But then again, I have not done as much R&D and note taking as maybe I should and as I am sure Brian has done.
 
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