Stihl MS 650

16 MS 650, MS 660
Condition Cause Remedy
Engine speed drops quickly under
load – low power
Air filter dirty Clean the air filter
Throttle shutter not opened fully Check throttle rod
Tank vent faulty Install new tank vent
Fuel pickup body dirty Install new pickup body
Fuel strainers dirty Install new fuel strainer
Leak in fuel line between tank and
fuel pump
Seal connections or install a new
fuel line
Setting of high speed screw (H)
too rich
Rotate high speed screw (H)
clockwise (leaner), no further than
stop
Main jet bores or ports blocked Clean the carburetor
Pump diaphragm damaged or
fatigued
Fit new pump diaphragm
Impulse hose damaged or kinked Fit new impulse hose