The Forestry Forum

General Forestry => Chainsaws => Topic started by: MS251_88 on December 17, 2016, 01:33:00 PM

Title: STIHL MS251 full throttle problems
Post by: MS251_88 on December 17, 2016, 01:33:00 PM
hey guys i need a little advice. i have a STIHL MS251 that i bought a few years ago. i cut up 5 cords of wood with it when i bought it brand new and it worked awesome. but one day my brothers saw broke so i offered to bring mine to his place and saw up some wood for him. when i was filling the saw up with gas he picked up a junk of wood and a bunch of sawdust fell off the junk and went inside the gas tank. the saw hasnt worked right since. i took the carburetor apart 3-4 times now, blew the carb out with an air compressor, blew out the gas line as well but still no luck. it seems like the saw idles fine and works well between little to half throttle but when i engage the full thottle the saw bogs out once theres strain on it. its worse when i tip the saw sideways to cut a tree down. not as bad when im junking it up for fire wood. seems like you can play with the H, L, and LA screws all you want and nothing seems to work. i cleaned the spark arrestor as well. only thing i havent tried is a new plug...anyone have any suggestions? thanks in advance!!
Title: Re: STIHL MS251 full throttle problems
Post by: Caloren on December 17, 2016, 02:38:03 PM
Your fuel filter should have taken care of any sawdust that fell in the tank, if there was a LOT of dust you might have to change the filter. If that doesn't help sounds more like a hole or split in the fuel line.
Title: Re: STIHL MS251 full throttle problems
Post by: Lnewman on December 17, 2016, 11:29:15 PM
I recently had the same problem with my MS 441.  Was cutting in zero degree weather.  Then I remembered reading in the manual that I should run at partial throttle for a bit before putting the saw into the cut.  That worked for me
Title: Re: STIHL MS251 full throttle problems
Post by: ladylake on December 18, 2016, 08:08:26 AM

I wouldn't blame it on some sawdust in the tank either unless it really clogged the filter.  How cold is it ?  Saws need more fuel in cold weather and if the limiter caps are still on you might not be able to open up the adjusters far enough.  Steve
Title: Re: STIHL MS251 full throttle problems
Post by: Trooney on December 18, 2016, 09:51:32 AM
I'm with ladylake. Usually if it bogs when leaning on it it needs more fuel. Trim those limiter caps and richen it up a little bit.
Title: Re: STIHL MS251 full throttle problems
Post by: MS251_88 on December 18, 2016, 12:08:34 PM
hey thanks for the reply! what exactly are the limiter caps?? thanks!
Title: Re: STIHL MS251 full throttle problems
Post by: MS251_88 on December 18, 2016, 02:17:51 PM
i found out that those limiter caps are those little plastic things just outside of the H and L screws! i took them out but the weather is on the plus side here today! when it cools down a bit again ill try adjusting her. thanks for the info guys much appreciated!
Title: Re: STIHL MS251 full throttle problems
Post by: Gearbox on December 18, 2016, 02:28:02 PM
If you took the gas line off to clean the carb . Replace it if it is the least bit hard it could be sucking air therealso you may have poked a hole in the line when you took it off the first time . Used pliers ?
Title: Re: STIHL MS251 full throttle problems
Post by: ladylake on December 19, 2016, 11:35:32 AM

Hopefully its just tuned for warm weather, I have to adjust every one of my saws when it gets cold.  Same symptoms, doesn't want to rev up and bogs easy. Steve