There is two fuel-to-air adjuster screws on this type of Carburetor, but this video shows you how to get results with adjusting just the largest and most accessible of the two.
In this video I'm going to show you how to adjust the type of 2 Stroke Carburetor with a single adjuster Screw. This style of carburettor fits Weed Eaters / Weed Wacker / Line Trimmers/ Strimmer / Brushcutter, but also Hedge Trimmers and some Chainsaws. But aside from what the carburettor fits, we have the single adjuster screw. I have been asked many times how to adjust this type of carb.
Ok, so, the adjustments on these are actually very simple indeed. Much more simple that the type of carburetor with the a 'H' and 'L' screw setting such as what we see on some other chainsaws etc.
First of all then, we will look at how to adjust the High RPM. The following is an explanation of how I do this procedure, and I am NOT saying it the the best or quickest way.
With all safety precautions met, I start the engine. I Revv the engine to MAX RPM. I take an appropriate screw driver to the single adjuster screw at the center of the carb (Not the single screw situated at the top of the Carb. This one is adjusted later!). I then start to slowly turn the screw Anti- clockwise until I can hear the engine start to change it's tone to a Rich/Lumpy sound, and the engine RPM starts to reduce slightly (If I was to keep turning in this direction, the engine RPM would continue to lower and the engine would probably stop due to too much fuel flooding the engine). When I then turn the screw back in the opposite direction (Clockwise) slowly, so I can hear the engine RPM start to increase and become smoother.
If I was to keep turning the screw in this direction then the engine RPM would increase for a very short time before reducing and becoming weaker whilst continuing the turn. This would be due to the engine not receiving enough fuel. So I bring the screw back to a nice medium point somewhere between the two extremes, but, just on the edge of being very very slightly Rich of fuel. This is to make sure that there is a good supply of 2 stroke fuel going into the engine with it's accompanying lubricating 2 stroke oil, but not too much that the engine efficiency suffers for it.
Well, that is the High RPM sorted, now for the Idling Speed. The Idling adjustment screw is the small single adjuster screw situated at the top side of the carburettor, above the High speed adjuster screw that we have just set. So from idling, I screw in the screw (Clockwise) if I need higher idling RPM and outward (Anti clockwise) if I need less idling speed. I usually reduce idling speed enough so that the strimmer head (if on a weed eater) stops turning but maintaining a good RPM, and increase the speed (screw clockwise) if I feel the engine is running very low, of course. It's really that simple!
The Two Stroke Carburetor can seem complicated initially, but with some explaining this can be de mystified.
I hope you find this video useful, and I really hope you enjoy it.
Many thanks indeed
Craig Kirkman (Owner and Creator of The Repair Specialist Channel)
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