20 Most Recent Stihl FS 85 Weed Eater Questions & Answers

I'm not sure of the year of your trimmer but that model in good running condition should sell for around 100 dollars.

Stihl FS 85 Weed... | Answered on Sep 11, 2020

Carb jets need adjustment.

Stihl FS 85 Weed... | Answered on Sep 04, 2016

You will find the needle-valve inside the the Carburetor reservoir bowl. Just be sure that the bowl is free of any dirt before putting it back together.
Good Luck
Rich Lilja

Stihl FS 85 Weed... | Answered on Sep 04, 2016

Hello David,
You most likely have 1 or 2 problems causing this problem, both which have to do with the carburetor reservoir bowl.
1. The bowl is contaminated with dirt in with the gas causing the port to be clogged and won't allow gas to be siphoned into the carb /engine.
2. The rubber gasket on the top of the bowl is cracked due to the alcohol in the gas and needs to be replaced!
Good luck!
Rich Lilja

Stihl FS 85 Weed... | Answered on Sep 04, 2016

Hi Trevor
Here are a few things to check.

Sounds like you have dirt/debris in your caburetor jets,fuel passages or a diaphgram that is becoming non-flexible.
Check/Clean/Replace your Air Filter, a dirty air filter can make your engine run to rich with fuel.
Also be sure to check and clean your spark arrestor in the exaust,if you have one installed on your engine.
Note:Before you disassemble the carburetor:
Write down on a piece of paper or take a picture of how the linkage attaches to your carburetor for later reference when you go to reinstall your carburetor.
Mark each piece with a awl, or some kind of instrument that will make an alignment scratch before you disassemble the carburetor into separate pieces.
That way you will know which way it goes back together when you reassemble it.
Sometimes you can get by with priming the carburetor or by using a very small shot of starting fluid and letting it run a few times like that, and it will flush the gunk out of the jets,but most of the time you will need to rebuild the carburetor.
Be sure to check your fuel tank for water and dirt/debris, if there is water/debris then you need to clean your tank.
Check you fuel line condition after a while they will degrade and need replacment.
If you need to replace your fuel line, cut the end of the fuel line to an angle for easy insertation into the fuel tank, see attached photo.
Check/Clean/Replace your fuel filter if you have one, normally they are located in the fuel tank of chainsaws and weedeaters.
When you remove your fuel lines from the carburetor be sure to make a drawing to how the lines are connected to the carburetor or take a pictue for later reference.
Normally the big line will be the line the fuel filter is connected to inside of the tank.The smaller of the two lines is the return to the fuel tank from the carburetor after it is pumped thru the carburetor by the primer bulb.
Make sure you are using fresh fuel...and oil if your using a two cycle chainsaw or weedeater with the oil to the right mixture...too much oil as it can cause hard starting and excessive smoking.
If the chainsaw/trimmer is over a couple of years old, then I recommend that you buy and install a new carburetor repair kit,because the diaphragm will get hard and that will cause it to be hard to crank.
The diaphgram may look good and flexible, but it can be deceiving and not act as a fuel pump as it should because it has become too hard and will cause hard starting,start and run and shut off, etc.
When you clean your carburetor, I recommend that you use a laquer thinner type cleaner to clean and dissolve the laquer build-up in the float and needle jet passages.
Be sure to remove all plastic and rubber parts before using the laquer thinner because it can dissolve the plastic parts and render them unuseable.
Be sure to use COMPRESSED AIR to blow out all the fuel and air passages.The higher air pressure is needed to blow some of the trash/debris from the fuel or air passages.
Be careful when blowing out the passages, because there are sometimes small rubber type seats in the bottom of some of the passages.
Keep in mind that the float (if you have one) for the carburetor must be level when you go to reassemble the carburetor or follow the instructions you get with the carburetor kit, or you could also ask the parts man that you get your kit from.
When you clean your carburetor and remove the jet screws, you will first need to lightly seat the jet screws.
But before you lightly seat the jet screws count the number of turns it takes to seat the jet screws from their original position.
Be sure to mark the turns down on a piece of paper.
That way when you put the jets back in, you know to lightly seat them first and then turn them back out to their original position before you started.
The little spring inside of the carburetor goes under the float arm.
That is where your fuel inlet needle/float valve is located...on the arm at the end.
Normally there is a small indention in the carburetor base and a small protrusion on the underneath of the float arm where the spring will be in the right postion for installation.
The spring will set in the indention and you will install the float arm with the needle/float valve and float rod into position over top of the spring,you will push down until it is in position and then you can tighten the screw that holds the float arm assembly in position.
Once you have your carburetor cleaned/rebuilt that should solve your problem.
Please take time to rate me

Fuel line trim12_21_2012_3_59_14_pm.jpg

Stihl FS 85 Weed... | Answered on Aug 03, 2016


? 6:55
Sep 16, 2011 - Uploaded by JEREMY FOUNTAIN Here is what I did for my fussy Stihl FS 250r trimmer....this after sitting all ... STIHL FS80 FS85 FC85 HS80 CARBURETOR ASSY 41371200614 ...

Stihl FS 85 Weed... | Answered on May 05, 2016

Hi, your model is an FS76, Could you please add a picture of your cutting attachment and I will try and help you.

Stihl FS 85 Weed... | Answered on May 01, 2016

could you add a picture of the particular head you're using.

Stihl FS 85 Weed... | Answered on Feb 27, 2016

do you have a spark? compression? and is fuel getting into the cylinder? more information please

Stihl FS 85 Weed... | Answered on Feb 27, 2016

possible vapour lock in the fuel tank. pop the fuel cap when it stalls, its probably under vaccum, check tank vent.

Stihl FS 85 Weed... | Answered on Feb 27, 2016

check air filter, and fuel tank vent, it could be causing a vapour lock

Stihl FS 85 Weed... | Answered on Feb 27, 2016

check for breaks in fuel line, check fuel filter.

Stihl FS 85 Weed... | Answered on Feb 27, 2016

broken or bent inner drive shaft

Stihl FS 85 Weed... | Answered on Feb 27, 2016

Not finding what you are looking for?
Stihl FS 85 Weed Eater Logo

77 questions posted

Ask a Question

Usually answered in minutes!

Top Stihl Garden Experts

ray gallant

Level 3 Expert

70853 Answers

Thomas Perkins
Thomas Perkins

Level 3 Expert

14850 Answers

bryan st

Level 2 Expert

123 Answers

Are you a Stihl Garden Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

View Most Popular

Stihl Garden

  • Stihl Garden

Most Popular Question

stihl fs 85 weed eater trigger

  • Garden