Fs38 question.

M

mikeinflorida

Forum Newbie

Joined

Sep 4, 2025

Threads

1

Messages

2

• Yesterday at 9:44 AM / Fs38 question.

• #1

Hello

I bought a used Stihl fs38 weed eater. The previous owner replaced the head with one that swings 2 plastic blades. The blades are stihl brand and are a hair over 4" long. My question is at 1/4 to 1/2 throttle the rpm are already pretty high, much higher than I think they should be. At full, the engine is screaming. Seems to be the engine needs more load. Does Stihl make a longer blade which would give me bigger cutting path as well as keep the rpms in check ?


Thx


Mike

 

S

slomo

Lawn Pro

Joined

Jul 14, 2019

Threads

80

Messages

5,703

• Yesterday at 11:02 AM / Fs38 question.

• #2

Trimmers, blowers and well most all outdoor powered gear are meant to run at MAX rpm, all the time. Why? Most are air cooled. The slower you run the engine the less cooling air is generated. Next category is lubrication. Same deal here. Trimmers are meant to be at full song after you pull the rope.

Put the stock head back on. Get rid of the Barby head.

 

Tiger Small Engine

Lawn Addict

Joined

Dec 7, 2022

Threads

3

Messages

1,531

• Today at 5:49 AM / Fs38 question.

• #3

slomo said:

Trimmers, blowers and well most all outdoor powered gear are meant to run at MAX rpm, all the time. Why? Most are air cooled. The slower you run the engine the less cooling air is generated. Next category is lubrication. Same deal here. Trimmers are meant to be at full song after you pull the rope.

Put the stock head back on. Get rid of the Barby head.

Click to expand...

You don’t have enough load on the engine. Why anyone would take the good line head off and install one where you have to constantly stop and add more line is beyond me. You have to have the trimmer line all the way out for correct load, and let it rip. 2-strokes love full throttle.

 

StarTech

Lawn Royalty

Joined

Feb 19, 2020

Threads

114

Messages

12,369

• Today at 7:48 AM / Fs38 question.

• #4

 

A

Auto Doc's

Lawn Addict

Top Poster Of Month

Joined

Sep 7, 2024

Threads

17

Messages

1,327

• Today at 7:57 AM / Fs38 question.

• #5

2-strokes like this Stihl FS38 are designed to run wide open throttle for cooling and to keep the centrifugal clutch fully engaged. Putting a wider cutting head on it puts too much stress on the components.
An FS38 is a light duty DIY trimmer. If you want commercial results, consider a larger trimmer.

 

M

mikeinflorida

Forum Newbie

Joined

Sep 4, 2025

Threads

1

Messages

2

• Today at 9:30 AM / Fs38 question.

• #6

Not looking for commercial. Just me and my yard. I'll see if original owner still has original head.

 

StarTech

Lawn Royalty

Joined

Feb 19, 2020

Threads

114

Messages

12,369

• Today at 10:25 AM / Fs38 question.

• #7

Upon some research through the Stihl docs here the FS38 poly head used are three versions not two blade version. And how old the FS38 there are three different poly cut heads. One for the older FS38 and two for the newer FS38.

 

A

Auto Doc's

Lawn Addict

Top Poster Of Month

Joined

Sep 7, 2024

Threads

17

Messages

1,327

• Today at 12:15 PM / Fs38 question.

• #8

Hi Star Tech,

The head with plastic blades is an optional head that Stihl offers. It comes with hardware for different models or adapters can be purchased.

 

StarTech

Lawn Royalty

Joined

Feb 19, 2020

Threads

114

Messages

12,369

• Today at 1:46 PM / Fs38 question.

• #9

Auto Doc's said:

Hi Star Tech,

The head with plastic blades is an optional head that Stihl offers. It comes with hardware for different models or adapters can be purchased.

Click to expand...

Of course. There is the Auto Cut, Dura Cut, Fix Cut, and Poly Cut versions. I was just noting that the OP said he had a two blade Poly Cut version which Stihl does not offer for FS38