How to Reset Common Carburetors Back to Factory Setting for High & Low Speed Screw Adjustment ?

Adjustment Screws and functions

Idle mixture screw: controlsthe intake of fuel to adjust the engine for optimum running.
TAS screw: controlsthe intake of air to adjust the engine’s idle speed.
High speed screw: (marked H on carb) - This is the adjustment that controls the proportion of fuel in the combustible air/fuel mixture at cutting speed.
Idle speed screw: (marked L on carb) - This is the adjustment that controls the proportion of fuel in the combustible air/fuel mixture at idle speed.
Turn H/L screws clockwise, fuel will be leaner; Turn H/L screws counterclockwise, fuel will be richer. The amplitude for each adjustment is 1/4 turn.

Solutions for a “won’t start” problem after carburetor replacement

1. Check if the cylinder assembly is leaking, start the engine up after adding some gasoline into the inlet, then listen carefully to whether there is gasoline firing in the cylinder.
   
   2.Check if the ignition coil and spark plug are normal.

3.Check if the carburetor pressure hole of the gasket is aligned.

4.Check if the primer pump can pump fuel properly.

5.Check whether the fuel system or air filter are clogged. Follow the steps above, reassemble the parts, and your machine will work normally.

*Replace the float bowl seal gasket in time if gasoline is leaking.

*Remove the carburetor bottom cover and clean the float needle if the carburetor is still leaking after the engine stalling.

*If there is gasoline coming out from air filter after the engine stalling, check the carburetor and ignition coil.

*Turn off the fuel valve after the engine shuts off.

*If the machine is going to be left for a long time, the gasoline in the tank should be emptied, the fuel valve should be turned off, and the gasoline in the machine should be discharged to avoid corrosion to the plastic parts of the carburetor by gasoline.

*Carburetor is a highly sensitive, precision instrument designed to control fuel and air mixture ratio. Always Keep it clean to gain proper performance.

*Pure gasoline is preferred, followed by E10 gasoline, to extend the lifespan of the engine.


*The fuel of 2-stroke engines is mixed fuel, and the ratio of oil and gasoline should comply with user manual.

1. Adjustments for 2-stroke butterfly valve diaphragm carburetors

   1. Method to adjust idle speed: Start the engine and warm it up for 1 minute after installing a new carburetor. If the idle speed tends to surge up and down, then turn the idle speed screw clockwise to reach highest RPMs(4500 to 5500 for reference) for fuel complete combustion. Professionals can assure the RPM according to its sound, if the RPM is higher or lower, then turn the idle speed screw counterclockwise to reach 2800-3200 RPMs until turning the idle speed screw to the highest idle speed. Consistently pressing your trigger down to keep it running and flipping over your machine to simulate the working condition and check if it runs properly.

    

   2. Method to adjust high speed: Pressing and holding your trigger down to run as fast as it can. Turn the high speed screw to reach a proper RPMs(10500 to 12500 for reference). Consistently pressing your trigger down to keep it running and flipping over your machine to simulate the working condition and check if it runs properly.

    

   3. Method to reset the carburetor in case of confused parameters during adjustment: turn the idle speed screw clockwise 1/2 to 1 turn; turn the idle speed screw clockwise fully, and then turn counterclockwise for 1.25 to 1.75 turns; the high speed screw is also turned clockwise fully and then turn back for 1.5 to 2 turns.

    

    

    

   Adjustment for 2-stroke rotary valve diaphragm carburetors

   1. Method to adjust idle speed: Start your engine and warm it up for around 1 minute. If the idle speed tends to surge up and down, turn the idle speed screw to let RPMs stabilize around 2800 to 3200. Consistently press the primer bulb and check if the engine is going to stall.

    

   2. Functions of the idle mixture screw: If your machine isfailing to reach the ideal idle speed by adjusting the TAS screw, then fine tune the idle mixture screw. Turn it clockwise to increase the fuel output while turn counterclockwise is to decrease the fuel output. This should only be done by professionals.

    

   4. Method to adjust high speed: Pressing and holding your trigger down to run as fast as it can. Turn the high speed screw to let the RPMs stabilize in an ideal range(9000 to 10000 for reference). Carburetors without the high speed screw cannot be adjusted. Flip over your machine to simulate the working condition and check if it runs properly.

    
   
   

    

   Adjustment for float carburetors

   Solutions for the “won’t start” problem after carburetor replacement:

   1. Check if the ignitionswitch is in the ON position, the fuel valves of the fuel tank and carburetor are in the ON position and the choke is closed when starting it up.
   2. If there is a fuel pump in your machine, check if it can pump fuel normally and the cleanliness of the air filter and fuel filter.
   3. Check whether the solenoid valve of the carburetor can be switched on and off normally.
   4. Check if theignition coil and spark plug are functioning normally.
   5. Check if the cylinder is leaking, start the engine up after adding some gas into the inlet, then listen carefully to whether the fuel is firing from the cylinder

    
   
   
   

   Idle speed screw adjustment: the RPMs of idle speed surges when turning the screw clockwise; the RPMs goes down when you turn the screw counterclockwise. The idle speed screw is for adjusting the idle speed of the engine (refer to the model manual for specific values).

    

   Idle mixture screw adjustment: the mixture of gas and air tends to be thinner when turning the screw clockwise; the mixture tends to be thicker when turning the screw counterclockwise. Fine tune the screw if the engine has slightly running issues.