Outdoor Power Equipment and Small Engines - Stihl FS80 Questions for troubleshooting

Hi All,

A friend gave me a low hour FS80 he was having issues with, basically saying "If ye can get it to run ye can have it." Well, he was right, it starts very hard and bogs under any real throttle.

If someone could answer a couple of Q's it may help me on my troubleshooting. fyi I'm using fresh fuel with stihl oil.

- How "fat" is the spark supposed to be on these Stihls. When grounding the plug to the head, I can see a small blue spark at the plug (if in the shade) -- but I'm used to seeing it be a lot more robust. We did bypass the ignition switch with the same results. The magnets seem good on the flywheel. The plug "looks" good -- it is a bosch and is clearly getting fuel. The plug was gapped out to .30 to get it started, then backed down to .20 as per spec.

- The FS80 owners manual I downloaded shows a 3 screw carb adjustment setup (H, L, LA) -- This carb only has the low idle (LA) screw and one other. Anybody seen this setup?

- How likely is a Stihl dealer to give out info and sell parts on these given that I did not purchase the trimmer new and the owners manual is **sparse** on information besides the obvious stuff.

Thanks kindly,
George//oldscout2

Have you pulled the spark arrestor out and checked it? That sounds like it could well be the problem.

The dealer will sell parts to anyone who wants them, regardless of where they bought the equipment. I think most dealers are at least somewhat helpful even when the equipment you have isn't from them.

With the proper .020" plug gap, you won't find an explosion of a spark so I dare say you have sufficient spark. The "LA" adjustment is the idle speed screw adjustment (RPM's at idle) and the other adjustment should be the "L" fuel screw (low speed fuel circuit). The LA screw will be set at no particular setting, just at the right idle speed. The other screw should be set, initially, to 1 1/4 turns out form seated and may need a final adjustment once the engine is brought up to operating temperature.

Well, both suggestions were good and it now runs like a scalded dog. I had cleaned the spark arrestor as one of my previous steps but went back and really scrubbed it out on cheese's advice. Also tuned the carb as puey61 suggested. The trimmer is running great (and a lot stronger than I thought it'd be), much appreciated guys.

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