Weak Output Or Change Of Speed; Other Engine Problems - Husqvarna K770 SmartGuard Workshop Manual

7.4 Weak output or change of speed

Symptom/Category Cause
Compression is good Air has gone through the fuel pipe joint.
and there is no flame
Air has gone into the fuel pipe because of a
out.
crack or pin hole.
Air has gone through the pulse pipe.
Air has gone through the insulator and carbu-
retor installation part.
Air has gone through the oil seal.
There is water in the fuel.
The piston is burned.
Carbon blockage in the muffler.
Overheating. The engine is running lean.
Blockage because of dirt in the air channel for
decreasing temperature.
Blockage because of dirt on the cylinder fin.
Low quality fuel is being used.
The level of carbon has increased in the com-
bustion chamber.
The spark plug tip is red hot.
Other. The air filter is too dirty.
Too high load.

7.5 Other engine problems

Problem Cause
When the engine rev- The clutch spring is broken.
olution decreases, the
The clutch is open because of rusty clutch
blade does not stop.
bolts.
When the engine rev- The drum bearing does not move.
olution increases, the
blade does not rotate.
Strong vibration. The blade not balanced.
The vibration dampening element is broken.
72 - Troubleshooting
There are no sparks at the spark plug
There are no sparks at the spark plug
Solution
Make sure it is tight.
Replace.
Make sure it is tight.
Replace or tighten the gasket.
Replace.
Empty and clean the tank, then fill with good
quality fuel.
Remove the burn with a file, or replace.
Clean.
Repair or replace the carburetor.
Clean.
Clean.
Replace with good quality fuel.
Clean.
Champion RCJ 6Y/NGK BPMR 7A: Adjust to
0.5 mm.
Replace the air filter.
Lower the load.
Solution
Replace the clutch spring of the engine.
Remove corrosion from clutch bolts, apply
grease and assemble.
Replace.
Install a new blade. Make sure that the right
bushing is used.
Replace.
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