Stihl Chainsaw Carburetor Adjustment


Stihl chainsaws’ have three carburetor adjustment screws

(LA) Idle Speed screw – This controls the engine speed at idle. If set too low, the saw will die. If set too high the chain will run. This is dangerous.

(L) Low speed adjustment screw – This is the low speed jet. This is the adjustment that controls the air/fuel mixture at idle. Adjust this screw too rich and the chainsaw will blubber and die at idle speed. Adjust this screw too lean and the engine will starve. The saw will race or surge. An extremely lean adjustment will also cause the engine to die.

(H) High speed adjustment screw – This is the high speed jet. This is the adjustment that controls the air/fuel mixture at high RPMs. Adjust this screw too rich and the chainsaw will blubber, too lean and it will over rev

Safe Basic Settings

Screws (H) & (L) – Turn the adjustment Screws (H) & (L) down onto their seats (clockwise). Back them off 1 complete turn (counter-clockwise)
Screw (LA) – Turn (LA) Idle Speed screw until the chain stops. Then turn counter-clockwise one quarter of a turn.

Fine Tuning – Screw (L)

Erratic idling behavior; poor acceleration – Idle setting too lean; turn low speed adjusting screw (L) counterclockwise until engine runs and accelerates smoothly. Readjust screw (LA).

Exhaust smokes at idle speed –Idle speed setting too rich; turn low speed adjusting screw (L) clockwise until engine speed drops. Then turn screw back one quarter turn and check that engine still accelerates smoothly when you open the throttle. Readjust screw (LA).


chainsaw carburetor adjustment

Adjustment of the high speed adjusting screw(H)not only affects the power output but also the maximum off-load engine speed. If the setting is too lean (screw turned too far clockwise), the maximum permissible engine speed will be exceeded. This can cause engine damage, brought about by lack of lubrication and overheating in particular. Corrections to the setting of the high speed adjusting screw may be carried out only if an accurate tachometer is available to check the maximum engine speed of 13,000 rpm (with bar and correctly tensioned chain).

When the engine is tested at the factory the carburetor is set to obtain a slightly richer mixture to ensure that the cylinder bore and the bearings receive additional lubrication during the break-in period. This setting should be left as it is for the first three tank fillings. The high speed adjusting screw may then be turned no more than 1/4 turn clockwise (leaner mixture). Caution: The engine”s maxi­mum permissible rpm must not be exceeded! Note that even slight alterations on the adjusting screws have a noticeable effect on the engine”s running behavior. Only carry out carburetor adjustments after cleaning the air filter and warming up the engine.

If you have no means of checking the maximum engine speed, do not set the high speed adjusting screw (H) any leaner by turning it (clockwise) beyond the basic setting Above!

« Stihl Chainsaw Carburetor Tuning ChartStihl Chainsaw Troubleshooting Guide »

Stihl Carburetor Part BreakdownThis how-to works with a Husqvarna, husky, Jonsered, Poulan, McCulloch, Craftsman, Homelite, Echo chainsaws as well as a Stihl 009, 009L,011, 011T,012, 017, 018, 018C, 019, 019T, 020, 020AV, 020T, 021, 023, 024, 025, 026, 026 PRO, 028, 029, 034, 036, 036 PRO, 036 QS II, 039, 044, 046M, 066M, 088M, MS170, MS180C, MS191T, MS192T, MS200, MS200T, MS210, MS250, MS260, MS260 PRO, MS270, MS280, MS290, MS310, MS360, MS360 PRO, MS360 QS II, MS361, MS390, MS440, MS460, MS660, MS880, HT100, HT101, HT70, HT75 STIHL – Virtual factory visit

  • Anonymous

    Great saw Derek. Did you try my Stihl Chainsaw Troubleshooting Guide? If you have spark and a new plug with the correct gap, use a small squirt bottle of mixed fuel and, squirt a little gas directly into the carburetor. If it starts, clean the tank, fuel line, and carburetor thoroughly.

  • Anonymous

    Thanks for your input David. Most of the comments on this post got jumbled when I moved to Disqus. I was able to repair most, but your comment was lost.

  • Anonymous

    (Edited by a moderator) explanation: Most of the larger comments on the post were truncated when I move the comments to Disqus. I edited no ones comments I just tried restored them to the original.

    David thanks for your input it is helpful I changed this guide because of your comment, and I urge readers to look over all the comments on this page you’ll find lots of useful information.

  • Frank California

    I just downloaded the pdf file for the 017 from http://www.stihl.com they will even mail one to you if you like

  • Anonymous

    Sounds like the rings have seized to the cylinder wall, this happens a lot after storage. A little air-borne humidity has gotten into your engines cylinders causing the pistons to seize up. Take out the plug and give it a try, If your lucky your muffler is clogged. Get a good penetrating lubricant and spray it into the cylinder and let it go to work, after several hrs-days try to turn the engine over. Work it at the crank not the pull cord. Go slow.

  • Anonymous

    Great saw Derek. twodogs maybe right if their is no scoring it could be starving for fuel. try a new plug with the correct gap clean the tank, fuel line, and carburetor thoroughly.

  • Hansumboy4u

    034 ur cylinder is full of fuel when the plug is in it wont pull over ppl it over with the plug out realy fast about 20 times and then put plug it and don’t choke it ur carb it needs a kit put in it diaphragm and needle

  • Jaimegarciaramirez

    I have a Wrigley’s 025 starts on choke but when I push thaw lever for moral start it shuts off

  • Roy

    buy her an electric chain saw and a long extension cord. It’ll start everytime.

  • Thedodgeman899

    i have a newer 029 that died when was using it and now will not start or fire any clue how to get it to work?

  • Johnny varnadore

    you can still find the points but u are going to have to sent it to sihl to get them set proprley i own a small engine repair bussiness ive been doing it for over 20 years and iv always sent it to the factory but if u can set them u can come work for me

  • Johnny_brvo2u

    i dont have valves

  • Johnny_brvo2u

    thanks to ethonol for the white gunk u are going to have to take your carb all the way down idel screws and all leave the welch plugs in get u a can of carb cleaner spray every hole u see put it all back together idel screws go all the way in back out two and a half turns thats a starting point for yor h and l make sure the gasket goes on first then the diphram hope this helped johnny’s small engine repair and service llc

  • Blomberg

    Had ms 192 c-e light weight saw for 2 years, worked fine until it quit. Found Welch plug in Zama carb had dropped out. It was cemented in and not punched. Tried to cement in with Permatex #2, ran 10 minutes and quit. Plug had fallen out again, cement dissolved in gas. So made and used oblong punch to set Welch plug followed by tiny amount of old bottle of clear nail polish around edge. Dried overnight. Saw has been running with good power last two weeks. Gasoline with alcohol dissolves most cements. Have Seal-All from ACE on hand in case have to cement plug again.

  • Anonymous

    Have you determined whether or not you have spark? That would be the first step. Pull the plug out, connect it to the plug wire, and let it touch a metal part of the saw. Then pull the cord while watching the electrode on the plug. If it sparks, chances are that the ignition is ok and we can go further. If not, you have ignition problems.

  • Anonymous

    Sounds like an air leak. If you can run an engine on full choke, you definitely have an air leak somewhere, you would have to have the mixture screw bottomed out to run that lean. check to make sure the carburetor screws are tight. If those are good check the cylinder bolts are tight too. An old trick to find a vacuum leak is to get it running and spray choke or carb cleaner around it–when the revs go up listen for a change in exhaust note. If no air leak are found the carburetor may have a problem and need to be rebuilt.

  • Jphogg

    jeff have 390 ms shoots gas from carb why?

  • Interesting blog. It would be great if you’re able to provide additional information regarding it. Thanks lots

  • ED K


  • I became just browsing here and there but happened to be you just look at this post.

  • Tjones399

    Derek, I just had the same issue. I rebuilt the walbro carb on my stihl 026, new gaskets, replaced the screen you were talking about. I also used a can of carb and choke cleaner and sprayed it thru all the holes. Even removed the high and low needle valves and sprayed thru them. I re-assembled the carb (great video on you-tube). But I also replaced the fuel line and filter. It started on the second pull woooohoooo. Make sure you get the correct fuel line. If yours is an older stihl you may need the straight fuel line, not the one with the pre-bend in it. Also check your fuel tank vent. If it is clogged it wont let the carb pull gas. Also when looking at your carb from the handle make sure the impulse line (right side bottom) is fully attached to the carb. Now reassemble and seat the L and H screws Clockwise to stop. Back each one out 1 1/4 turns left. Now choke and start. Again search youtube for stihl 048 carb rebuild video.. very helpful.

  • Bearh3526

    Gentleman, need help. I been in small tools for 20. Mostly partner and large construction equipment as well as small tools. Here the problem, have a Stihl TS 460 on the bench came in not running. Been sitting. Actually looks like someone found it at the bottom of a lake. Anyway, torn it down cleaned it up. Low compression, so replaced piston and jug and rings. Compression back up. Replaced carburetor with new one. Clean gas tank and replaced filter and fuel lines.
    Problem is I can not get any fuel to pump to the carburetor. have a clear fuel line. Did a pressure test on fuel line and tank no leaks. Did a leak down test on Piston and jug. Tested ok. Also did a pressure test on new carb just to make sure no leaks. So I figure I should have had a leak some where. Still scratching my head. Can any one give me something else to look for or do. Oh yes replace plug and yes I fired it up with direct gas to carb and it ran on that fuel only and shut off

  • Frank

    I’ve been working on the same problem for about a week with a Stihl 028. I’ve rebuild the carb several times, cleaned it out, and it still only runs when I spray gas in the carb. I have to believe it is a problem with the carb, but I’m scratching my head as well.

  • Anonymous

    Sounds like you have all the bases covered but here goes.
    Change the fuel line and filter if the fuel line has a pin hole in it, the engine will suck nothing but air.
    If the fuel diaphragm has a hole in it, it won’t suck in gas either.
    Also blow through the supply hose from the tank to make sure it isn’t plugged.
    If you still can’t get air through, try to follow the fuel’s path, and blow though each hole with compressed air. You should be able to find the obstruction that way.
    Look through the carb and you should see the reed valve. This is a piece of springy metal that covers the hole. Press on it gently to see if it can move towards the crank case. If not, the valve is stuck and fuel can’t get in.
    Make sure you are using the correct fuel/oil mixture.
    Seat it mixture screw all the way in gently return to position.

  • Muleskinner750

    what are the carb screw settings for an stihl 015L?

  • Jason

    I have a brand new stihl ms290, have run roughly 5 tanks of gas through it. The saw starts fine and runs fine as long as it is horizontal or with the bar tipped up. When I tip the bar down it sputters out. Proper mixture of gas that is new within the last month…any suggestions?

  • Tjones399

    Take the carb out and rebuild it with a gasket kit. Pay carefull attention when dis-assembling it so you rebuild it with correct gasket placement. Ebay is a good place to find kits or the walbro website. Also replace needle valve and make sure the spring is centered under the metering arm and the screw is tight that holds down the metering arm. If you still have problems check your fuel tank vent and make sure spark screen in the muffler is clean. Sounds like the needle valve is not closing and opening properly letting fuel run down thru the intake manifold. Really if the saw is brand new Stihl should repair it for you for free…Should be under warrenty..

  • Tankersley Dusty

    Hi to who ever might help! I have a ms390 I had a bad fuel line witch burnt up cylinder and piston. So I got a new piston and cylinder (non stihl) and took it too a stihl dealer and they put it together. And adjusted carb. It ran good for a bit(few minutes) now it dies when I give it throttle? But still idles fine! What’s wrong?

  • Crawfjames

    hi i have a stihl 009 was going strong but now it starts sometimes idles then when u go 2 peak the revs the saw cuts out. have cleaned the carbi and filter but still no go, can any1 help with advice and help me with the (L) AND (H) settings please

  • Redtick696969

    I have an 028 stihl that wont start well runs for 2 seconds lol!!!!! I changed fuel, air filters and spark plug fuel lines it had sat fer 6 years!! and the h and l screws were not in it i cleaned carb too

  • Anthony


  • Jayarnold24

    I have an old stihl 041 AV. I started it up ran two tans a half tanks of gas through it and all of a sudden it started bogging down when I tried to rev it up to cut. Thought it might be too hot so let it cool down and cleaned it up. After checking the air filter and a cool down, it starts up fine but again I can not get it to roar to life just idle. Please help.

  • Jayarnold24

    I have an old stihl 041 AV. I started it up ran two tans a half tanks of gas through it and all of a sudden it started bogging down when I tried to rev it up to cut. Thought it might be too hot so let it cool down and cleaned it up. After checking the air filter and a cool down, it starts up fine but again I can not get it to roar to life just idle. Please help.

  • DaveDell

    My Stihl Farmboss 290 has always (2 yhears now) balked at full size cuts. It runs fine. Cuts smaller branches. If I engage any more than about 6 inches of the saw it bogs down and doesn’t cut. It does this regardelss of blade/bar combination. It’s sharp. The exhaust port and spark screen is clean as a whistle. Actually, it’s suspiciously clean with hardly any darkening of the spark screen let alone any carbon deposits. It starts and runs great with smooth accelleration. I can’t adjust the hi end to a richer setting (counter clockwise – out) because it hits a stop at the 3/4 turn. Adjusting the low end makes no difference in either direction. Adjusting the high end leaner (clockwise to less than the recommended 3/4) makes no difference. It idles fine.

    I’m using a 20 inch bar and chain. One of those low kickback chain/bar combinations with 11 teeth on the roller. It’s the ones that came with the saw new. Would going to a 10 tooth roller and chisel blade help? Would going to a 16 inch blade help?

  • D Ricker

    I have a McCulluch 1-40 with some wear but by no means worn out. Compression 120 psi, strong pull. Adjusting carb is the problem. I cannot seem to get carb adjusted properly w/o clutch and chain engaging. I can’t seem to find how much the throttle screw (touching carb butterfly) enters the equation. Should it just be barely touching to keep engine idling or screwed in further which will speed up chain even further? Any thoughts?

  • David

    I need to know the needle valve adj for an old model 031av

  • Tezyoung

    i own a 088 and it wont start theres no spark but can feel sum shock on lead when pulling

  • Arn

    Tezyoung……….Try a new plug.

  • Anonymous


  • jimmi

    stihl 044,problems solved,would fire but not start,used a business card too set the ignition between flywheel after a clean up,good tiingle at plug lead,still no go,cleaned carb completly,plus tank outlet/overflow (hard tiny screws too remove and clean,boiling water worked),still no go,seams flooded,take plug out and to my surprise the tiny bit of porcline just below plug gap was movng up and down 2mm,replaced plug with a spare…followed tips on H & L settings…welllahhh shes gong mint,thanks too google search and this forum,life s looking good for my many other c/saws..088 is next, toasted pistion,will replace with aftermarket parts 9 times cheaper than stihl orginals ; )

  • Beatricehartzell

    i have a 019t stihl it has good compresion, its geting fire to the new spark plug and it started one time , i put gas directly in the carb and it still will not start. it dont leak gas and i just cant seem to get it started can some one help me here ?

  • Prestonsarge

    I have a ms 390 the carberator need something I put a carberator from my 310 on the 390 and it works. So it the carberator put in a new diaphragm did not work.What the next thing to do?

  • Neobarbaric

    The carb with cleaner off sprays a lite mist of gas sprays on my hand then stalls out running nicely at high RPMs. Needs to b choked again then it will start. It is an older Stihl av24.

  • Doug Smo

    Exhaust may be blocked/clogged

  • Doug Smo

    Also, don’t under estimate nature. I had a generator that worked one day. Then 2 days later, it would not even turn over. Thought the engine had seized up. So I started taking it apart to find that mice had built a nest using insulation. The nest was built in the flywheel stopping all rotation.

    Some insect may have built a nest inside of the muffler. Take the muffler off and try to turn it over.

  • Doug Smo

    Gas gas gas. GAS LINE may have a crack/hole. It will let you get some gas up every once in a while or the fuel filter in the gas tank is clogged. Notice that when it runs and dies there will not be any gas in the primer bubble after it dies. If there is still gas in it then coil may have gone bad. other than these issues check the compression. Should read 90 – 110 psi.

  • Doug Smo

    sounds like the fuel filter is not laying at the bottom of the tank. check this!

  • Doug Smo

    Did the spark plug cable touch the engine head and melt through the insulation maybe. Sounds like it is grounding out before the spark plug. or replace the coil. or wiring for on/off switch could be faulty. was spark plug replaced?

  • Anonymous

    CC on (h) also check the screen in the exhaust, Air filter, Fuel filter, Collapsing kinking or week fuel line, clogged screen in the carb, or a vacuum leak.

  • Anonymous

    (h) screw controls the high RPM jet. also check the screen in the exhaust, Air filter, Fuel filter, Collapsing kinking or week fuel line, clogged screen in the carb, or a vacuum leak.

  • Anonymous

    Fuel tank vent, Air filter, Fuel filter. Hope your not over heating from an over lean condition.

  • Anonymous

    Yea 088! Try q-tip some muriatic acid on the cylinder scoring till it puddles then clean up with and 600 grit wet/dry sandpaper with a little water. rinse and repeat several times. The Stihl cylinder is much better quality. after market pistons work great

  • Anonymous

    do you have compression?

  • Anonymous

    good cleaning and rebuild.

  • don

    try cleaning the screen in the carb

  • Anonymous

    Are you getting spark when it’s hot? If not you have a bad coil.

  • Chuck Luke

    I have an 009 that starts,runs and cuts great from a cold start. Once it has run for a few minutes it bogs and stalls if on the gas. It will start right back up but will bog and stall again as soon as I give it gas. what do you think the problem is? Thanks.

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  • ozzie

    i have the same saw, when it was new it kept getting oil and saw dust in the points and would not start. as it was still new and under warranty the dealer changed over to trans. ignition system and that cured the problem. that has been a least 20 yrs ago.

  • ozzie

    i have the same saw, when it was new it kept getting oil and saw dust in the points and would not start. as it was still new and under warranty the dealer changed over to trans. ignition system and that cured the problem. that has been a least 20 yrs ago.

  • jonathan carrasco

    Hi, hope someone can help.
    I have a Stihl 009 which will not start unless a small amount of fuel is poured directly in the carburetor, once it starts like this it runs fine…..?

  • jonathan carrasco

    Hi, hope someone can help.
    I have a Stihl 009 which will not start unless a small amount of fuel is poured directly in the carburetor, once it starts like this it runs fine…..?

  • peter

    Hi I have an 046 and it has worked fine but after a time in the shed with new fuel and clean filters it s impossible to start and run. Immediately the decompression is off the timing seems to be so advanced that it is impossible to operate. A new electronic ignisian was installed and it made no difference. My mechanic has two others that are similar. Someome suggested cutting a new keyway on the flywheel but this shouldn’t be necessary as it worked perfectly earlier. Please help! [email protected]

  • Justin Jay Winter

    I’ve got an AV024 that I just rebuilt the carb on and added a new bar as it was missing it’s original (put an 18inch on it). got it all back together, first DIDN’T adjust carb settings after rebuilding it (flow lines were clear but inner membrane was pretty bad and was bogging the whole thing down) tried starting it and got it to run for about 2 seconds on the 3rd pull with choak, after that i got nothing. readjusted carb settings to technical specs (fully tighten and then counterclock turn 1 full turn on each) and i got nothing… was getting WAY TOO MUCH fuel to i tightened fully again and then did a 1/4 turn back and i’m just not getting a pbit of a pop here and there but if i loosen more it just spitting more fuel… tighten and it goes far too lean.

    rebuild kit is for a Walbro, carb is a Walbro. as stated before, needle in the kit is NOT the same as what’s in the carb… so the original was re-used. as for gaskets, gaskets were fine but the replacement membrane was NOT the standard clear poke-a-dotted membrane, instead it’s a transparent blue plastic sheet… there was no other membrane with the same cutout so i was forced to use it pre-ssuming it was correct as it’s cuttout was identical to the original.

    -I’ve got air, air filter is letting in plenty of air
    -I’ve got Fuel…. boy do i have plenty of fuel. so much so that it’s spitting out the exhaust on almost the lowest possible settings.
    -I’ve got spark… must have checked that a thousand times… it’s an old bosche but it sparks just fine.
    -I did notice the pressure line going from the carb to the lower crank case is using an identical hose to that of the fuel hose and i’m pretty sure it’s suppose to use a different one… however if that was the issue, i wouldn’t be getting fuel so it’s obviously not causing a problem if it’s sending plenty of pressure for the fuel to be pushed into the carb. and according to the parts list, the normal hose that goes there is about the same in inner diameter and length, just a different outer molding.

    I’m a diesel mechanic and a metal fabricator… yet for some reason this little pea burner is being the most frustrating thing I’ve ever worked on… any ideas?

    Before I went to rebuild it, it started just fine but bogged REALLY bad and acceleration with the chain clutch disengaged (no load at all) was poor at best with it taking about 5 seconds to get to full speed at all full throttle.

  • Jason Jones

    I have had my MS290 for 4 years started cutting out at idle, replaced air filter and started messing with idle adjustment that worked for a day. Took it in and the local shop found a busted piston. Wanted what I thought was too much to replace so I bought new cylinder/piston rebuild kit and did it myself.

    Did I need to put some sort of lube in the crankcase (bottom of cylinder)? I used 2 stroke oil to lubricate the new bearings, crankshaft, and piston for insertion but not to excess.

    It fired right up upon reassembly but the problem remains I can get it to stay idle by backing off the idle speed adjustment but afraid to keep messing with the adjustments. Anything I am missing? Thanks

  • Simon Auh

    Im trying to get a troubleshooting manual for Stihl 070. Any pdf for download?

  • jeremy

    why can’t I get my stihl chainsaw 024 started. I’ve been trying 2 adjust my H/L . but can’t get set just right. I need help/

  • J

    Make sure you have the off switch set to the choke or start position. Those two positions have compression release to start them