I have a stihl 021 that doesn't want to idle, and bogs when going from low rpm to higher rpms, once on the high end it runs fine, just wondering where to start and what to look for. Thanks, Scott

Turn both low and high adjustment screws carefully clockwise all the way in - do not overtighten.. Then back out each two full turns. Set the idle speed control for highest setting. Prime and start and let it run and warm up for about 15 seconds - then lower the rpms a tad and then adjust the low end screw for highest rpm. Then reset the idle to lower reasonable level. You may have to go back and forth with those two adjustments till it runs fine at low idle speed..

Then accelerate to highest speed and set the high adjustment for highest rpm. Then go from idle to high speed. If not smooth a small adjustment on the high speed screw is in order. Keep doing that until you get a nice smooth transition form low speed to high speed.

carby idle adjustment or a carby kit and clean needed

carby has a high and a low rpm jets

STIHL MS 290, 310, 390

https://www.stihlusa.com/.../instructionmanuals/stihl-ms-290-310-390-owners-instructio...
Instruction Manual - improper use can cause serious or fatal injury. MS 290. Warning! ..... model. Safe use of a chainsaw involves. 1. the operator. 2. the saw.

how did you adjust a pre-programmed ECU idle settings ??? please be more specific

the vehicle's ECU is pre-programmed to run higher than 1000 rpms while in "open loop mode" then idle back down to ~750 rpms once the engine reaches operating temperature "closed loop mode"

did you tap into the OBD 2 port and used a laptop to change the settings?

Adjust the high speed screw on carb

Install a new spark plug

Use fresh fuel

Check out related help links to troubleshoot these problem:----Click the link below:---Idles Fine but RPM jumps in drive mode?http://technoanswers.blogspot.in/2012/07/idles-fine-but-rpm-jumps-in-drive-mode.html
---------Mitsubishi Lancer rpm needle bounces?http://technoanswers.blogspot.in/2012/02/mitsubishi-lancer-rpm-needle-bounces.html
--------How to adjust rpm on 2009 dodge charger SRT8?

http://schematicsdiagram.blogspot.com/2011/12/how-to-adjust-rpm-on-2009-dodge-charger.html
---------
Engine cuts out at 3000 RPM?http://schematicsdiagram.blogspot.com/2011/12/engine-cuts-out-at-3000-rpm.html

---------

Cold start problem and vehicle shudder around 2500 to 3500 rpms
http://repairhelpcenter.blogspot.com/2012/10/cold-start-problem-and-vehicle-shudder.html

---------
High rpm in neutral? Inconsistant high RPM in neutral?http://technoanswers.blogspot.in/2012/02/high-rpm-in-neutral-inconsistant-high.html

-----------
Jetski Sputters and Low RPM? http://whatisbyme.blogspot.in/2012/07/jetski-sputters-and-low-rpm.html

--------
Fuel Injection Problem And RPM suddenly increaseshttp://whatisbyme.blogspot.in/2012/07/fuel-injection-problem-and-rpm-suddenly.html

----------
2005 Toyota Highlander: Engine runs hard RPM below 3000?http://whatisbyme.blogspot.in/2012/05/2005-toyota-highlander-engine-runs-hard.html

---------
1987 Toyota Camry: RPM Drops going Up hills?http://whatisbyme.blogspot.in/2012/05/1987-toyota-camry-rpm-drops-going-up.html

-----------
Cruise Control stops working, Excessive cranks to start the engine and RPM goes max 2500 http://whoisbyme.blogspot.in/2012/07/cruise-control-stops-workingexcessive.html

----------
1990 Toyota 4Runner: Engine cuts off when reaches 2000 RPM?

http://whatisbyme.blogspot.in/2012/05/1990-toyota-4runner-engine-cuts-off.html

------------
1999 Toyota Camry: Erratic stalling and high engine RPM at idle?

http://whatisbyme.blogspot.in/2012/05/1999-toyota-camry-erratic-stalling-and.html

---------
1995 Toyota LS: Misfire at idle or low RPMhttp://whatisbyme.blogspot.in/2012/04/1995-toyota-ls-misfire-at-idle-or-low.html

-----------
Lexus RX: Tapping noise under Valve Cover At Low RPM?http://technoanswers.blogspot.in/2012/04/lexus-rx-tapping-noise-under-valve.html

----------
These will help.
Thanks.

The "H" is the adjustment for the higher rpm range
The "L" adjusts the acceleration and low rpm
The last is the Idle screw

First check the air cleaner. Clean or replace it. You need to set the mixtures for the carburetor. You will find a Low and High adjustment screw usually on the left or right side of the carburetor on the outside of the housing. At idle turn the screw in or clockwise until the rps starts to decrease. Then start turning it out till you hit max idle rpms. Turn screw back in a quarter to half turn and it should be idling smoothly. Be careful here and get someone to hold saw if necessary but hold in throttle to full speed and do the same with high adjustment screw. turn it in till rpm starts to drop then back it out until you get to max rpm and it won't go any higher then turn it back in a half a turn. After adjusting the mixture it might be necessary to readjust the idle speed.

Find the 2 screws. There will be a (h) high and (L) low. These are for hig rpms and low rpms. First tighten the screws. Then unscrew them about 1-1/4 turns. Then start the saw and let it warm up. Start with the high rpms first pull the trigger all the way then adjust the screw in 1/8 turns either way until it is running good at high rpms. Then work on the L rpms. Get the saw to idle then pull the trigger, there should not be any hesitation when going from L to H rpms. Just adjust the low same as the High. They have to work together so if the high is good and the low is not just right turn the h a small amount. If you have any more questions let me know

The main jet need cleaning.(you should clean them all though)

Main Jet: Main jet comes into play at three-quarters open to full throttle conditions. CRITICAL to high-speed engine operation. Not only does it meter the gas into the engine, it can aid in cooling the engine as well.

Please rate this Fixya

the vehicle has a rev limiter built in. this is what you probably feeling. Are you passing? The rpm's shouldn't be that high at 60