# Stihl FS91 line speed?



## slimbo3006 (Jun 12, 2022)

So My old FS85 might be nearing her end...

looking at the possibility of replacing it. Probably either with a FS70R or FS91R. I know the 91 is a 4 mix engine and thus turns slower than a traditional 2 stroke. To compensate for this, is the gearing in the head different so as to give the FS91 a similar line speed to the FS70? If not, just seems like you would be losing a lot of RPM on the sting head. 

I have used a fs111 before but it had a metal blade on it so I really couldn't judge the speed of the head. 

I like that the 91 is also a solid shaft, not that I run brush blades often, but if I choose to....


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## ironman_gq (Jun 28, 2022)

I wouldn't worry about it, I've got the FS131 and it does everything I need and I rarely use full throttle. Way more than enough line speed.

Your FS85 is rated at 7500rpm at the trimmer head, the FS91r is 7150, not that much difference


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