Stihl FS40C String Trimmer First Use and Review

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By Allan Douglas | Aug 23, 2017

I recently wrote about my adventure in trimmer shopping, this is the follow-up to that piece as a review of my new Stihl FS40C string trimmer.

Stumbling Start

Testing was delayed by the fact that I didn’t have a 1-gallon gas can. I have several 2-gallon cans, and one is a can into which I pump precisely 2 gallons of gas for use in my 2-stroke equipment. I have some gas/oil mixed up but that’s a 40:1 mix for my older tools. The Stihl FS40C string trimmer uses a 50:1 mix.

I bought a six-pack of synthetic oil for the Stihl, each bottle mixes with one gallon of gasoline. I figured I’d use that can of new gas and two bottles of oil and be all set to fire up and see what it can do. But the manual and some commentary online talk about the need to use the gas/synthetic oil mix within 30 days or it begins to decompose, and using degraded gas/oil can void the extended warranty (four years) Stihl offers. In fact, in reading the warranty there are several ways they try to get out of paying for repairs during that second two-year period.

So I popped down to the closest hardware store and bought a 1-gallon gas can, mixed in the Stihl oil, and filled the trimmer’s gas tank.

Firing Up My Stihl FS40C String Trimmer

The controls and start-up procedure are standard and familiar. This does have a convenient feature that opens the choke automatically if I gun the engine a little after start-up.

I pushed the primer bulb five times and the trimmer started up on the third pull. It would probably have started on the first or second had I primed it more. The first two presses on the bulb passed nothing but air — being brand new and never run.

One of the issues I’ve had with my old trimmer was keeping it running while at idle. It tended to die if I didn’t gun the throttle a little while walking from one spot to the next. If I had to set it down to open a gate it was sure to quit on me; but it started up again, so it was no big deal.