Stihl fs74 help

matty12345

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May 5, 2018
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Hi,
Basically the problem is when I rev the engine it bogs down and dies. Even if I try to gently apply revs it just dies. It starts and idles fine usually though. I fitted a new fuel filter but this made no difference so I got a new carb. Fitting this didn’t make any difference so I think I can rule out the carb. My dad suggested it could be the coil but I thought I would ask on here first to get your opinions before I get a new coil. Any advice would be greatly appreciated,
Matty :smile:
 

Fish

Lawn Pro
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Aug 2, 2013
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How is the fuel line?

Have you tried richening the mixture screws yet?
 

matty12345

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Yea the fuel lines are all fine and I tried adjusting the screws on the carb too but that didn’t help
 

Telesis

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Apr 19, 2017
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Check to see if you have a plugged muffler. Also, check that the shaft drive isn't 'stuck' in some way that as the clutch tries to engage, it's unable to rotate and thus kills the engine. (disconnect the shaft assembly at the engine and isolate the two to see if the engine still dies)

Good luck!
 

Been There Done That

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Check the spark arrestor in the muffler first. If it's carboned up, take a propane torch and burn all of the crap off it, then brush the residue off with a wire brush. Also check your air filter. If both are good, then it's likely a carb issue. If you're mechanically inclined, check the metering diaphragm (under top cover) and the fuel pump diaphragm (bottom cover, usually only one screw holds cover on). Check for holes, brittleness, hardening, or deterioration in general. While you have the covers off, spray carb cleaner around the inlet needle (bottom of the carb), through all passage holes in body (be careful not to dislode filter screen) and blow out gently with commpressed air. Pay attention to positioning of diaphragms/gaskets when you remove the old ones, and assemble the new ones in the same manner.
 
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