Stihl FS250 carb adjustment

[BiodieselNC]

Alright guys, i know this isn't a chainsaw, but maybe you guys can help me with this. I just got a Stihl FS250 brushcutter, it is a newer model and was manufactured early 2010. Guy bought it this summer and decided it was too much and sold it to me. Thing runs great but there is only one problem. No H and L screws on the carb!!!!! All it has is the idle adjustment. On the cover/shroud there is a black rubber plug blocking where the adjustment holes would be. and the carb has H and L marked on the side, but there are no adjustable needles sticking out. I have heard these respond well to muff mod and tuning but obviously i can't tune this. Is it possible to swap to a different carb? Anybody have any insight on this?

Btw, i pulled the muffler and carb off, the piston and rings are in perfect condition, and the little motor pulls 160psi compression. I am running my mix a little rich until i can do something about this carb!

 

[Roanoker494]

What carb does it have on it now? Walbro, Zama? What is model number on the carb?

 

[lcso10]

Being that you said there were no adjustments screws other than the LA, it makes me think that this is an old stock unit. May have been sold this year but it has been sitting somewhere.
Anyway with that aside, you can replace that carb with the # 4134-120-0653It will be the adjustable Zama. They retail for close to $60.00.

 

[willsaw4beer]

Run straight up 50 to 1. Extra oil ends up leaning it out because the oil takes the place of gas so there's a leaner fuel/airl ratio.
I run a fs250r for a living, the 4 mixes are great too but the 250 is the #### plain and simple.

 

[BiodieselNC]

I'll run 50:1 i just feel it's running a bit lean, thats all. Don't wanna mess up such a nice strimmer, and i dont mind $60 for a carb if i can tune it and do a muff-mod. I like the 4-mixes because of the low end torque, but the top-end on a FS250 just blows everything else away!