# FS250 Carb Setting at WOT



## John Lyngdal (May 18, 2018)

The specs for the FS 250 are:
Engine power to 1.6 kW (2.2 bhp) at 9,000 rpm
Idle speed: 2,800 rpm
Cut-off speed (rated): 12,300 rpm
Max. output shaft speed (cutting attachment): 9,150 rpm

I took the high speed jet on the rich side at WOT to 9000 rpm then, leaned it back to 10,000 rpm with the string head installed and the line to full cutting length. I'm running 93 alcohol free gas at 40:1 with Amsoil Sabre, as the engine is running like a milling saw, WOT for long periods of time. This all seem reasonable, or should I adjust the WOT setting?


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## DND 9000 (May 19, 2018)

You can use this setting. It is definitely on the rich side. The cutoff speed range without cutting tool (electronic speed
governor) is between 11,300 to 13,300 RPM.


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## John Lyngdal (May 19, 2018)

DND 9000 said:


> You can use this setting. It is definitely on the rich side. The cutoff speed range without cutting tool (electronic speed
> governor) is between 11,300 to 13,300 RPM.



I was concerned about the Max. output shaft speed (cutting attachment): 9,150 rpm specification and running it faster than that.


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## ironman_gq (Jun 11, 2018)

Whats the gear ratio on the cutting head? If it's around 1.3 then setting the max WOT speed at 12,300 will still give you a safe output speed of 9150


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## DND 9000 (Jun 12, 2018)

Gear ratio is 1:1,4 on the FS 250.


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## ironman_gq (Jun 12, 2018)

DND 9000 said:


> Gear ratio is 1:1,4 on the FS 250.



Should be safe at the max engine speed then


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## John Lyngdal (Jun 12, 2018)

Thanks everyone! I didn't know that there was gear reduction on the head.
Time to adjust the carburetor to the optimum setting and let it rip.


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