golfmaniac2
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- Joined
- Jun 9, 2023
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What is the procedure in adjusting the low speed and high speed carb needles?
Yes, both of the screws. the new cab was exactly the same, which I was surprised.Did your old carb have both of those screws ?
So you have bought a junk carb off Scamazon and this is not the carb the engine came with .
The High speed ( throttle open ) is determined by the main jet at the bottom of the transfer tube
In the side there should only be one screw , the long one with the spline on it which is the idle mixture screw and sets the air:fuel ratio
The screw behind the welch plug is the idle volume screw which controls the volume of the air-fuel mix entering the cylinder when the throttle is closed on the throttle stop
I have not seen one of these for decades .
Usually it is done with a series of small holes
And your picture is way too small to be of much use .
I will admit, my knowledge of lawn mower carbs is very very basic.What OP is a Nikki clone carburetor. As said the screw with serrations and small double D is the idle mixture. The other screw is the idle speed and you will need a tach to set the speed at 1750 rpms.
This idle mixture adjustment may not even work on the current carburetor. If this is the case, the engine would be surging at idle and off load high idle; even after the static governor adjust has been done. A couple years ago I ran across one these carburetors. Internally there is an idle mixture limiting jet that may need resizing so the idle mixture screw will work.