Stihl weedwacker wont start


Old 05-22-04, 02:15 PM
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Join Date: Jan 2003
Posts: 56
Stihl weedwacker wont start

Stihl SF40 weedwacker... 2 cycle....good spark...gas coming in but the original owner ran it with straight gas....thus he gave up...could the rings be cashed and not drawing in the gas as it should... took out plug and dropped in gas with no avail....i know every 4 cycle i get at least a spur but nothing on this lost at what to look 4... carb is clean and diaphram is in great shape.....
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Old 05-22-04, 04:01 PM
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Join Date: Feb 2003
Location: southern louisiana
Posts: 365
If it was ran with only gas and no oil, then the cylinder is probably scored. You can tell by removing the muffler and taking a look at the cylinder/piston/rings. If it is scored, then the piston traveling in the cylinder will not create the required vacuum to suck gas into the cylinder, it will not seal the ports that lead to the combustion chamber and crankcase, and most importantly, it will not seal well enough to create enough compression (which is why it won't start even though you pour gas strait into the cylinder). When you try to start the trimmer, does the engine turn over really easy? Try putting your finger over the spark plug hole while pulling the rope, hold you finger on the hole with moderate pressure. If there is enough compression to push your finger off the hole, then there might be enough compression to start the engine. Hope this helps. Good luck!!!!!!!!

Last edited by mower17; 05-22-04 at 04:13 PM.
Old 05-23-04, 01:10 AM
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Join Date: Jul 2001
Location: USA
Posts: 16,814
Hello saldog6!

I agree with Mower17. Running a 2 cycle engine without 2 cycle oil is the equivalent of running a regular 4 cycle engine with no oil. It ruins the piston and cylinder quickly, and often ruins other parts. Hate to tell you bad news, but it would probably exceed the value of the unit to repair it. Check the compression, or you could remove the muffler and look in the cylinder and at the piston skirt. If they are scarred up, you know it's had it.
Old 05-23-04, 05:59 AM
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Join Date: Jan 2003
Posts: 56

thats what i kind of figured as was givin to me and yes after looking into the muffler that ring is not even a goner...oh well...maybe if i open the crank up i can glue them all back together.....hehe

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