STIHL FS 280 Oil mix ratio and huge revving problem!!!

[trini_fella]

Hi guys, i've recently started using my dad's Stihl which he owned for like some 8 years but never used.

First question, should i use a 40:1 or 50:1 ratio?? I've looked through alot of manuals for other trimmers and I see most of the older model like the FS 160 n 180 (which I think might be the closest to mine) use a 40:1 ratio. The newer ones specify a 50:1. I can't seem to locate my manual anywhere online and it doesn't even have it listed to order (guess i really have a dinosaur on my hands).

Secondly, and much more importantly, I've been noticing a problem when revving the machine. When I pull the throttle all the way in, instead of revving up right away, it stalls and takes about 10 seconds before the engine fires right up to max speed. Changed the filter and the spark plug recently but that's about it. It really makes using the machine impossible right now. I really need some help. Thx in advance

 

[Lawnranger]

First check the muffler and exhaust port for any carbon build up or restrictions and clean as necessary. Most likely the carburetor diaphragm is starting to harden and become less flexible which means it will start to run leaner (less fuel) and that is a bad thing. Since Stihl now owns Zama the cost of these carburetors has come down significantly and replacing the carburetor will save you a lot of time and potential head aches. Get the numbers stamped in the carburetor body and call your local Stihl dealer and request price & availability on your specific carburetor. Clean out the fuel system and use fresh mix. Check the fuel lines and replace if necessary - that goes for the air filter & spark plug, too.

I can't advise you on the mix ratio except to use what the machine calls for but I use Stihl Ultra (gray bottle) two stroke oil at 50:1 in all my equipment even if it calls for 40:1 as the synthetic oil outperforms the mineral oil products. YMMV

 

[xp14629]

It should be 50:1. Ur local stihl dealer can print a new manual off of he dealer website. Look at the gaskets on and around the carb. I have been seeing a lot of them where it looks like an oily residue around the carb mounting because one of the gaskets is leaking externally. It will normally cause the hesitation or burp Elton are experiencing.

 

[trini_fella]

Okay you guys will do and respond wit outcome. Thx so much!!!