BSARGE

While adjusting the throttle linkage this morning(trying to troubleshoot another problem) I noticed that when I would manually move the throttle arm to close the carb(no pushrod attached) when I let go, it would on its own open back up! Like it was spring loaded...all my other engines would stay when you left it. It is a 46fx...what would cause this?

-Bill

aerowoof

gravity.

js3

My Feedback: (3)

Depending on what motor it is, there is sometimes a spring on the carb barrel.

scratchonly

I have had some carbs do this. Don't worry about it.

JohnBuckner

My Feedback: (1)

As js3 indicated the FX series uses a compression spring inside the barrel which pushes the barrel outward (not rotate) all the time. This is a common arrangement on many dual needle carbs.

On the barrel is a concentric grove and a guide screw protrudes into this grove. The purpose of this grove is to physically move the barrel out as the throttle is opened and vice versa. This moves the midrange needle further or closer to the jet and in this way the midrange mixture can be controlled closely.

If there is no pushrod hooked up and carb is in excellent condition with no gauling the spring has a tendency to push the barrel outward and if friction is low enough then this outward movement will cause the grove to react to the pin and the motion will be converted to rotary motion opening the throttle.

Not unusual bill its just as it ought to be, enjoy your engine. Of the OS's the FX is one of my favorites.

John

BSARGE

Thanks for the answers, that put my mind at ease, I have had several other O.S. motors and maybe I just never noticed it before...


thanks again!
-Bill