Question about Phazer 480 Mikuni B38-32 butterfly carburetors.


littlejohn said:
Yamadogger.....it's a pilot screw . No doubt , no question .
Click to expand...
Yes, however some pilot screws regulate air. But the facts that:
1. the screw is on the engine side of the carburetor.
2. that the screw has a sharp pointy tip.
and
3. RPM increases as it is turned in.

All this points to that it is indeed a screw which regulates fuel. I just want to make this 100% clear for anyone else who might be wondering this in the future :)

This really good video I found explains carburetors and the differences between fuel and air screws and how to identify them:
 
Both pilot and air screw regulate the air fuel mixture but a pilot screw meters fuel only that's why when you turn it out it richens the mixture due to more fuel being allowed to pass through that circuit. This also why it's opposite with a air screw because your metering the amount of air in the circuit when turning the screw out. They basically accomplish the same thing but one meters fuel the other air . Knowing which one is which is important because it matters which way you turn them .
 
I still believe that there is some air mixed with the fuel up at that screw. The air entry for the pilot circuit is at the opening of the carb on the airbox side.
 
Read about the idle drop test. It will explain all this.

Whether it's an air or fuel screw, you're still controlling the the air/fuel mixture at idle to 10% throttle.
 
The point is mute , whether it be a fuel mixture screw or a air screw your accomplishing the same thing below 1/8 throttle knowing which way to turn the screw is key . Hence the reason behind opening the air screw allows more air into the mixture versus opening the pilot circuit to allow more fuel . It's s all good in the hood just know what kind of screw your turning and what direction to go
 
You must log in or register to reply here.


Back
Top