Stihl FS80 won't run


Old 02-03-16, 11:17 AM
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Stihl FS80 won't run

Help !!!!

Pulling the rest of the hair out trying to get my trimmer to run right. It has an older TK slide carb installed that will not reach full rpm's. I have rebuilt carb, installed new fuel lines, replaced spark plug, checked exhaust for obstruction, and performed pressure test on cylinder. It acts as if running too rich even with the high and low speed screws tightened all the way in.
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Old 02-03-16, 12:18 PM
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Make sure the fuel/oil mix is right (should be about 50:1) and the fuel cap is venting.


Try starting with both the mixture adjusting screws (L & H ) at 1 1/2 turns out from lightly seated and the idle speed set to keep it running. Then turn in the low speed for max rpms, then the high speed for max rpms at full throttle opening. Redo the low for max and then set the idle speed.

If that gets you an improvement, go back to the high speed screw and turn it out 1/8 turn to drop the max rpms.

If that procedure isn't affecting the rpms, it may be better to replace the carb.
Old 02-03-16, 12:25 PM
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Did you remove the mixture screws and thoroughly clean the carb and install a kit?
Old 02-03-16, 12:46 PM
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Does gas drip out the carb throat when it is not running?
Old 02-04-16, 03:37 AM
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Yes carb has been cleaned several times as carb kit was installed. No fuel exiting carb throat when not running. Carb sets above tank and relies on inner pump to draw fuel (which it is). Fuel mix is 50:1 and will try needle adjustments this morning and advise.

Thanks all for the response(s)!!!!!
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