Stihl 4 Mix Repair Manual

							 
 
 
Remove Fan Wheel: BR 500, BR 550, BR 600. 
 
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  To remove the fan wheel on a  4-MIX® backpack blower, block the piston with the 
piston stop and use a ½ inch breaker bar with a 17 mm. socket to unscrew the fan 
wheel. Piston stop STIHL Part # 4282 890 2700.  
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  The mounting nut is molded into the fan wheel as one piece and has right hand  threads. 
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  It will be extremely tight, and may take one person to hold the engine and fan  housing while another applies pressure to the breaker bar. 
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  Do not use an impact wrench on any STIHL product. 
 
 
 
 
Engine De-Carbonizing Procedure.  
 
 
 
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  If a 4-MIX® engine is showing more than 10% leakage past the exhaust valve, the most likely cause is carbon build-up on the valve face. 
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  STIHL Engine Decarbonizing liquid  can be used to soften and flush out carbon 
deposits. Engine treatment involves putting the piston at top dead center on valve 
overlap, where both valves are slightly open at the same time. This is 360° of 
crankshaft rotation from top dead center on the compression stroke. With the 
valve cover removed this is easy to verify. 
;
  Then fill the cylinder with the decarbonizing liquid. 
 
STIHL 4-MIX ® Cam Timing: Backpack Blowers – 4282 Series  
  
						

							;  If the engine is being assembled and the flywheel is not in place yet, just be sure the 
piston is at top dead center to time the cam correctly. 
;
  To install the cam on the backpack blower engines, notice that when the piston is at 
top dead center, the cam lobe is pointing up when the alignment marks are 
matched up. Now install the dowel pin. 
 
Rotate the crankshaft until the tip (arrow) of the 
flywheel lines up with the ignition module as 
shown. 
 
Fit the cam gear so that the arrows (2) and (3) are 
in alignment with the notches (1and 4) in the 
cylinder.