Stihl FS240 brushcutter tuning...

[10/80]

I have a new Stihl FS240 brushcutter (done about 3 hours work) that I'm having problems tuning by ear, I believe the initial carb setting are 1 to 1-1/4 turns out....At 1 to 1-1/2 turns on the H screw its still not 4 stroking and seems to be reving far too much...I'm running a fuel / oil ratio of 32:1.

 

[EFSM]

I have a new Stihl FS240 brushcutter (done about 3 hours work) that I'm having problems tuning by ear, I believe the initial carb setting are 1 to 1-1/4 turns out....At 1 to 1-1/2 turns on the H screw its still not 4 stroking and seems to be reving far too much...I'm running a fuel / oil ratio of 32:1.

Does it have a blade on currently?

 

[Brad Button]

Why are you running 32:1?? All newer equipment calls for 50:1. Sooner or later, that 32:1 will give you problems.

 

[DND 9000]

Absolutely right with using 50:1. Modern oil of today is much better as it was in the past. These machines are built for 50:1 and run a very long time with it, if taken a little care. If you don`t have a tachometer and don`t know the proper settings go to your dealer and let the dealer check it and do the tuning. Also you will not know if you hear 4 stroking or if it is the electronic rev limiter, therefore a tachometer is needed.

 

[EFSM]

Most newer equipment is just fine on 32:1, but I wouldn’t run that in a brush cutter with a blade, because the engine hardly runs hot enough to burn that much and you may get a really gunky exhaust.

Take it to the dealer and have them look at it if it is still under warranty.

 

[MtnHaul]

I have an older FS240 and it's the only power tool I've ever had where the spark arrestor got gunked up and clogged even at 40:1

 

[10/80]

Why are you running 32:1?? All newer equipment calls for 50:1. Sooner or later, that 32:1 will give you problems.

How will adding extra oil cause problems?

 

[AVB]

How will adding extra oil cause problems?

It will produce a lot carbon and clog the spark arrestor for one thing.

Note has a speed limiter set at 12,500 rpm [10,500 rpm if RC version] so these rev a lot higher.

To properly adjust the carb you need a tach and then follow the following instructions.