Stihl FS 56 RC String Trimmer

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Old 11-19-18, 08:12 PM
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Stihl FS 56 RC String Trimmer

Iím working on a trimmer and Iíve gotten it to run. I put a new carb on it and new spark plug. It wasnít running for a few years before.

It will run full speed well. The primer bulb primes. Fuel flows well. It has new fuel hoses and new filter and new vent.

It wonít idle well. It seems to either idle 3/4 speed or idle too low.

I crank it up. Rev it up and it doesnít idle down much. So I adjusted the idle screw and it lowers some but Is still super high. Then I adjust the idle screw 1/8 more turn and I rev it up and it takes a while to idle down and then it idled super low and dies.

I have the low and high screws 1.5 turns out.

I just canít figure it out how to get it to idle where the head doesnít spin.

Itís very hard to explain. If you donít understand let me know and Iíll post a YouTube video tomorrow on what itís doing.

I just donít get it. Also. When on choke for some reason it revs up super high.

The throttle is not stuck. The throttle valve is closed when running super high.

Is it lean? Rich?

What am I missing. Iím getting frustrated.
 
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Old 11-19-18, 08:43 PM
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It's lean.

Set the throttle stop for the idle speed where it keeps running. Then adjust the "L" for max speed and turn it back out slowly to see if you can get the idle down.

If that doesn't work you may have a air leak, possible at a gasket or crank seal.
 
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Old 11-20-18, 06:50 AM
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Iíve been thinking it has an air leak. Where could it have a leak in the crank seal? I donít know much about that stuff. It has new carb gaskets. I think they are good. Could I spray some carb cleaner around to locate the leak?
 
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Old 11-20-18, 08:19 AM
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The crank seals may be a little tough to spray around. They would be on the starter rope end and the output shaft end. Those provide the seal at the crankcase.

If you have a leak, since you swapped carbs, it would be at the carb gasket. The one you have may not match the mounting surfaces or the bolts may be loose. You could spray around that area easy enough.

Is it a new carb or just a different carb? If new is it OEM or an aftermarket?

See if adjusting the carb mixture helps. It may take care of it.
 
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Old 12-30-18, 07:01 PM
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Fixed it

I ended up buying another carb. The other one had a broken idle air screw. It runs perfectly now. Idles great too. Cranks on second pull.
 
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