Chainsaw Carburetor Troubleshooting Diagnosis Repair Guide

TROUBLESHOOTING  
Chainsaw troubleshooting chart  
The different faults that can occur on the chainsaw are  
divided into four groups as follows. Within each group  
possible operating faults are listed to the left while the  
probable fault alternatives are listed to the right.The most  
likely fault is listed first, etc.  
Starting  
Idling (low speed) (continued)  
Idles with closed L-screw  
Worn needle / needle tip  
Difficult to start  
Adjust the L-screw  
Air filter blocked  
Leaking diaphragm / coverplate  
Control system sticking  
Worn lever arm in the control  
system  
Choke does not work  
Worn choke axle  
Worn choke valve  
Blocked fuel filter  
Blocked or broken fuel line  
Faulty diffuser jet  
Piston ring seized  
Blocked impulse channel  
Uneven idling  
Blocked fuel filter  
Blocked fuel line  
Leaking intake hose (rubber)  
Loose carburetor mounting  
Worn throttle valve axle  
Loose throttle valve screw  
Worn throttle valve  
Control system sticking  
Leaking control system (air or  
fuel)  
Carburetor leaks fuel  
Loose or faulty fuel pipe  
Hole in diaphragm  
Worn needle / needle tip  
Control system sticking  
Control system set too high  
Leaking control system (air or  
fuel)  
Loose cover on carburetor  
pump side  
Worn center knob in control  
system  
Hole in diaphragm  
Floods when engine is  
not running  
Worn needle / needle tip  
Control system set too high  
Control system sticking  
Leaking diaphragm / coverplate  
Leaking crankcase  
L-screw requires  
Blocked fuel line  
constant adjustment  
Control system set too high  
Control system sticking  
Leaking control system (air or  
fuel)  
Idling (low speed)  
Leaking diaphragm / coverplate  
Faulty diffuser jet  
Leaking crankcase  
Does not idle  
Adjust the L-screw  
Leaking intake hose (rubber)  
Loose carburetor mounting  
Loose or faulty fuel pipe  
Blocked fuel filter  
Too much fuel when idling Control system set too high  
Control system sticking  
Blocked fuel line  
Damaged control system  
Worn needle/needle tip  
Leaking diaphragm / coverplate  
Incorrectly fitted controlsystem  
Tank ventilator blocked  
Throttle valve axle stiff  
Throttle wire sticks  
Defective throttle return spring  
Bent valve axle stop  
Faulty diffuser jet  
Too rich idling  
Adjust the L-screw  
Worn needle/needle tip  
Control system set too high  
Worn lever arm in the control  
system  
Leaking diaphragm / coverplate  
Control system sticking  
 
TROUBLESHOOTING  
High speed  
Acceleration and retardation  
Will not run at full  
throttle  
Adjust H-screw  
Blocked air filter  
Does not accelerate  
Adjust the L-screw  
Adjust the H-screw  
Tank ventilator blocked  
Blocked fuel filter  
Blocked fuel line  
Blocked air filter  
Tank ventilator blocked  
Blocked fuel filter  
Loose or faulty fuel pipe  
Impulse channel leaking  
Blocked impulse channel  
Cover on carburetors pump  
side is loose  
Blocked fuel line  
Loose or faulty fuel pipe  
Blocked impulse channel  
Cover on carburetors pump  
side is loose  
Faulty pump diaphragm  
Leaking intake hose (rubber)  
Loose carburetor mounting  
Control system set too low  
Damaged control system  
Incorrectly fitted control system  
Leaking diaphragm / cover plate  
Control system sticking  
Blocked muffler  
Faulty pump diaphragm  
Leaking intake hose (rubber)  
Loose carburetor mounting  
Control system set too low  
Incorrectly fitted control system  
Control system sticking  
Faulty diffuser jet  
Blocked muffler  
Engine stops when  
throttle released  
Adjust the L-screw  
Adjust the H-screw  
Low power  
Adjust H-screw  
Tank ventilator blocked  
Blocked fuel filter  
Impulse channel leaking  
Blocked impulse channel  
Cover on carburetor’s pump  
side is loose  
Faulty pump diaphragm  
Control system set too high  
Control system sticking  
Faulty diffuser jet  
Too rich acceleration  
Adjust the L-screw  
Adjust the H-screw  
Blocked air filter  
Faulty pump diaphragm  
Blocked air filter  
Control system sticking  
Leaking control system  
Faulty pump diaphragm  
Faulty diffuser jet  
(air or fuel)  
Control system incorrectly  
assembled  
Loose diaphragm  
Hole in diaphragm  
Leaking diaphragm / coverplate  
Will not four stroke”  
Tank ventilator blocked  
Blocked fuel filter  
Trouble shooting methods  
Blocked fuel line  
Loose or faulty fuel pipe  
Impulse channel leaking  
Blocked impulse channel  
Cover on carburettors pump  
side is loose  
In addition to faults given in the above schematic, trouble  
shooting can be carried out on a specific component or  
specific chainsaw system. The different procedures are  
described in respective sections and are as follows:  
Faulty pump diaphragm  
Leaking intake hose (rubber)  
Loose carburetor mounting  
Control system set too low  
Leaking control system (air or  
fuel)  
Control system incorrectly  
assembled  
Loose diaphragm  
1
. Pressure testing the carburetor.  
 
 
2. Pressure testing the crankcase  
and cylinder.  
3. Pressure testing the decompression  
valve.  
 
 
4. Checking of the chain brake.  
Hole in diaphragm  
Leaking diaphragm / cover plate  
 
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