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Saw an FS94R listed for sale on craigslist. $20!

Typical Harry Homeowner situation. The mfg date says 2014, but the machine looks nearly mint. Barely used.
The owner said it wouldn't start, and he prefers electric tools anyway.

So here we are!
It had gas (unknown age) on it, then I added my own fresh mix.
It would not fire on its own, but it would start on starting fluid, and then run continuously on its own.
It did not have any power, and would not rev above ~30% at all.
It would idle for a long time until I stopped it.

I looked at the carb (did not remove), and did not see the typical "H, L" labels for adjustment.
I only found 1 adjustment screw, with a hex head.
I got the proper tool and adjusted it.
With that adjustment, I could get it to run "perfectly". It would start up on its own, run pretty well, idle, and sit at max RPM. Used it for ~10 minutes.

The issue is, why I put "perfectly" in quotes is because it's obviously operating at sub-par performance, but I assume it is 'satisfactory'. This machine does not 'scream' like I am used to with tuning 2-stroke tools. No matter how much I turn the tuning screw, I cannot get it to scream, which leads me to believe the screw has that classic plastic limiter thingy, but I cannot see it.

This seems odd to me, as the FS94R is specifically marketed as the "high power, superlight" alternative to the 4-mix trimmers.

Any tips?

First make sure the muffler spark arrester is clean,

Second according to the service there is three adjustment screws.


Basic mixture setting
Open the high speed screw H (1) 1 1/4 turns and low speed screw L (2) 1 1/2 turns from their seats.

Start let idle for at least 1 minute then set idle speed and mixture.

Adjust engine idle speed with a tachometer.
Adjust specified engine speeds within a tolerance of ± 100 rpm.

1. Turn the low speed screw L counterclockwise or clockwise
to obtain the highest engine idle speed.
If the engine speed is not between 3,100 rpm and 3,300 rpm, abort the
procedure, set the engine speed to 3,200 rpm with idle speed screw LA
and start again with step 1.

2. Use the idle speed screw LA to set the engine speed to 3,200 rpm.

3. Use the low speed screw L to set the engine speed to 2,800 rpm. Tune to the rich side.

Tune H for no more than 8500-9000 rpm tune rich if needed to prevent overspeeding. Ignition coil will limit the Cut-off speed (rated) to 9,800 rpm.

thanks for the post.
I could have sworn the top one (where arrow is pointing) was for the adjusting slack in the throttle cable.
I may have to look again.

Rotary piston refers to the carburetor's barrel.

The throttle cable must not be under tension when the throttle trigger is released since the control valve's
rotary piston may not close properly – the engine idle speed will then be too high.

For what it’s worth I have the fs94r when they came out and the model now like 2 years ago carb changed and location of the primer. I have messed with both of mine and it always seems to run real well when at factor settings with like the smallest of adjustments if any. These are cold blooded when first fired up cold like 4-5 pulls ( strato charged 2 stroke design) cold but 1 when hot. They read like 9,800 rpm on a tach and you will hear the rev limiter breaking up. Very good units good power and lightweight. I personally recommend you get a tachometer and read exactly how stihl tells you how to tune it. Look online service manual in carb section. I run .095“ line. Never tried .105” but might be a little big but I’m sure it’s fine It might slow down some zip. Thought I’d share my feedback. Hope this helps. Good luck