How to lean the filters

A lean fuel mixture is usually caused by unmetered air entering the motor. ( vacuum leak ). Have a look for any disconnected or broken vacuum hoses. Take a look at the air intake tube from the air filter to the throttle assembly to make sure it is tight and connected properly. A weak fuel pump or a restriction in the fuel filter can also cause a lean condition. Another problem could be a MAF sensor giving false readings.

Its Lean when you have more air then gas. Its Rich when you have more gas then air. So if its too lean check your air supply, filters, etc.

the lean on the side of carb before doing this replace air filter and plug then adjust if need most lean problems come from dirty filter or plug

lean codes are generated by faulty heated oxygen sensors
(HO2S) that are in the exhaust manifolds before the cat converters
their purpose is to read the exhaust gasses and report the composition to the ECM so that the air/fuel mix can be adjusted to maintain correct settings

P1131 Lack of HO2S-11 Switch ,Sensor Lean
P1151-Lack of HO2S-21 Switch ,Sensor Lean
PO171- System to Lean (Bank 1)
PO174-Systen to Lean (Bank 2)

Fuel Filter -Plugged
Low Fuel Pressure
Evap System -Leaks
Leaks - in ducting,air filter to throttle
PCV -Leaks
Exhaust System -Leaks
O2 Sensors-worn out

The engine can be running too lean (plug will show you that, very grey and dry.) crank seals leaking (lean) blocked fuel filter in the carby and pick up hose(lean) mixture setting too lean. You can try 1st by turning the H needle in the carby anti clockwise a 1/4 of a turn and try it. only the H needle. If this does'nt do anything check the others.

Fuel Filter and Pump-won't cause a lean condition,unless you don't have sufficient volume.
Air leaking in around injector O-Rings
Any kind of air leak,including intake manifold,loose O2 Sensors,Etc,Etc

6 ASE people should be able to figure it out!!!

Look at all Data on an Oscilloscope.
The fact that the computer reads lean--IS IT a lean condition.
Check tailpipe emissions to confirm,lean

It sounds rich to me try turning the "L" needle CW a little. CAUTION CW is leaner, to lean will destroy your saw. Adding the air cleaner leans out the mixture. Adjusting it with the air filter off can cause a run lean condition when installed.
Carburetor Adjustment by Madsens.com
http://www.madsens1.com/saw%20carb%20tune.htm

• CW is leaner; to lean will destroy the saw. If over tightened closed (CW) the adjustment screw faces are easily marred; marred adjustments are difficult to impossible to set properly.
• Clean the air filter; adjusting with a dirty filter can cause a run lean condition once cleaned and the saw run.
• Clean the spark arrestor and muffler; if the saw cannot exhale it cannot inhale.
• There are 2 wav (sound - idle & full - may not be highlighted) files that I find most helpful, I think you will too.

If you have more questions or need additional help please reply below and I will get back to you. Good Luck. HTH
Lou
Thank You for using FixYa.

Check fuel filter and air filter.

remove maf sensor and check for air filter debris on it, gently blow off debris taking care not to damamge the wires on the sensor. also check forvaccum leaks as this can cause a lean condition