jaj333

I'm adjusting idle screw for a guy. . On Os La 46 has a bleed screw hole. I know where it's at and how to close or open it.. Which is it. Closing the bleed hole lean it out or which way. I know if it smokes and sputters to rich. If it dies on acceleration it's to lean. Just can't remember to open or close the hole. Also know it's opposite of a 46 FX.

A. J. Clark

Open hole lets more air in thus making mixture lean. Just opposite of main needle.

jaj333

Thank you

LLRCFlyer

Here is a suggestion for setting the idle mixture. Opening the air bleed hole leans the idle mixture. Closing it richens the idle mixture. The idle mixture needs to be rich enough to provide enough fuel to accelerate the engine quickly when the throttle is opened, but not so rich that excess fuel accumulates in the crankcase which then floods the cylinder and quenches the glow plug when the throttle is opened rapidly. Here is a simple test for initially setting the idle mixture. After warming up the engine and setting the highspeed needle valve, run the engine at idle for at least 30 seconds. Then pinch and hold closed the fuel supply tubing to completely shut off the fuel supply to the carburetor. The engine should continue to run at idle for 7 to 8 seconds after the fuel supply tubing is pinched shut while it continues to burn off the accumulated fuel in the crankcase. If it runs longer, it is too rich and the air bleed screw should be opened some more to lean the mixture. If it quits in less than 7 seconds, then it is too lean and the air bleed should be closed some to richen the mixture. This method should get the idle mixture close to the ideal setting, where only minor tweaks will be needed to obtain the desired final setting.

tedsander

X2 on LLRCFlyers suggestion. When doing the pinch test, if set correctly, you'll get a slight increase in rpm just before it dies. If it picks up more than a couple hundred rpm, it is too rich. If it dies quickly, without any rpm change, it was too lean.

jaka54

All OS engines with air bleed carbs I have run during my 50 years in this hobby have never been running bad with carb factory setting which is half hole open! I would say that all engines with air bleed carbs are very unlikely to run bad with that factory setting.I do all my engine settings by listening to how the engine behaves , not with the "pinch test"!