Breaking in a Stihl 4-Mix

[HonorAndHonesty]

I bought a Stihl FS-91 trimmer which has a 4 stroke, 4 mix engine (you mix the oil with the gas). According to the users manual you should avoid using the unit at full throttle for the first 3 tanks of fuel, The unit has a rev limiter which it will hit at 3/4 throttle with no load on the machine and with the torque of it I would imagine you would only need full throttle in really heavy grass or brush.

The unit was started by the dealer and he warmed it up and ran it a bit to make sure it was good, I have started it up and ran it thru a few heat cycles thus far under no load, I ran it between 1/4 to 5/8 throttle and alternated RPM.

Any other tips?

 

[DuckRyder]

I'd trim some stuff with it (put it under a load)...

 

[spasm3]

I usually adjust my new 2 cycle stuff a bit rich for the first hour or so. Its harder now with limiter caps. I mix my oil with high test.

 

[HonorAndHonesty]

Originally Posted By: spasm3
I usually adjust my new 2 cycle stuff a bit rich for the first hour or so. Its harder now with limiter caps. I mix my oil with high test.


I suppose I could mix the oil ratio a bit richer. I run 93.

 

[spasm3]

Originally Posted By: 5AcresAndAFool
Originally Posted By: spasm3
I usually adjust my new 2 cycle stuff a bit rich for the first hour or so. Its harder now with limiter caps. I mix my oil with high test.


I suppose I could mix the oil ratio a bit richer. I run 93.


I mean richer, with the carb. Mixing heavier oil is not the same. I use amsoil at 40:1

 

[HonorAndHonesty]

Originally Posted By: spasm3
Originally Posted By: 5AcresAndAFool
Originally Posted By: spasm3
I usually adjust my new 2 cycle stuff a bit rich for the first hour or so. Its harder now with limiter caps. I mix my oil with high test.


I suppose I could mix the oil ratio a bit richer. I run 93.


I mean richer, with the carb. Mixing heavier oil is not the same. I use amsoil at 40:1


Im just afraid to pop the caps on the adjustments because of warranty, I honestly haven't looked if stihl has caps, the echos do.

 

[AnthemBassMan]

Hopefully it won't have the caps, just the splined adjustment screws. I also run Amsoil Saber at a richer mix at 50:1. I then adjust the carb screws for idle and throttle response.

L8R,
Matt

 

[spasm3]

Yes don't pop the caps, they will void the warranty. I just bought a high end chainsaw, and i see no way to even get around the limiters.

 

[dave123]

Originally Posted By: DuckRyder
I'd trim some stuff with it (put it under a load)...
+1

 

[bubbatime]

Break in? Its a trimmer. Use it.

 

[ironman_gq]

Fill it up and run it, just don't hold it WOT when it's not cutting. They use similar engines in all their blowers and they are pretty much running WOT all the time under load.

 

[bmwpowere36m3]

Fill it up with 50:1 (Stihl Ultra, extended warranty promo) and trim stuff... I try not to run it WOT with no load. At leas that's how I broke in my FS90.

 

[itguy08]

When I got my KM-130R in 2013 I brought it home and ran it like I stole it. First thing was pruning the trees (I got the pole pruner and wacker with it) at full tilt. Still runs great and after being stored all winter with a full tank of gas started on the 2nd pull. I love that little engine - plenty of power and, IMHO sounds great.

 

[The motor guy]

I hated my still 4mix. Had to sell it before I broke someone's window. Never could get that pos to stay at the same idle speed.