Stihl 162 Carburetor Adjustment (Tuning Guide)
On the STIHL MS 162, do not treat the carburetor as a standard H-and-L tuning unit. Its carburetor is factory-calibrated; the LA idle-stop screw is the only routine user adjustment, if fitted. Check fuel, filter, spark plug, and exhaust first. Follow the exact manual, and stop if the chain moves at idle.
If you have pulled the starter 30 times, the next step is not turning every screw you can find. A few basic checks can show whether the MS 162 has a fuel, air, spark, or idle problem, and help you avoid replacing parts without evidence. I use the same order each time: confirm the model, check the basics, then consider the approved idle adjustment.
Confirm the MS 162 and adjustment limits
The MS 162 carburetor is factory-calibrated, not a general-purpose carburetor for routine H- and L-screw tuning. Model variants and manuals can differ, so check the saw’s model label and matching STIHL instruction manual before making an adjustment. The LA idle-stop screw, if fitted, is the only routine user adjustment described here.
Look for screw labels before touching anything. Do not turn sealed or limited H or L screws, remove limiter parts, or copy settings from another saw. A screw position that works on a different model may be wrong for yours.
The manual is also the authority for your bar and chain. Common MS 162 setups use a 3/8-inch Picco chain, but pitch alone does not confirm a match. Bar length, chain gauge, and drive-link count must all suit the saw and bar.
Next step: Write down the exact model and check its manual before adjusting the carburetor.
Prepare the saw and work area
A safe baseline makes symptoms easier to judge. Work outdoors, wear eye, face, hearing, hand, leg, and foot protection, and keep people clear. Inspect the throttle trigger and interlock, chain brake, chain catcher, handles, bar, and chain before starting. Do not test-run a damaged saw.
Use fresh fuel mixed at 50:1 with STIHL two-stroke oil, or oil that meets the manual’s specification. Add suitable bar-and-chain oil. Check for leaks and confirm the chain is correctly tensioned. With the engine off and chain brake released, the chain should move freely by hand while wearing gloves.
Start the saw by the manual’s cold- or warm-start method, with the saw firmly supported. Keep the bar clear of people and objects. Do not rev the engine with the chain brake engaged. Once running, check that the chain stops at idle and that oil reaches the chain.
Check likely causes before adjusting idle
A saw that stalls, idles poorly, or will not start may have a problem that carburetor adjustment cannot fix. Fresh fuel, a clean air path, a sound spark plug, and clear fuel and exhaust paths are basic checks. I check these first because each can change how the engine runs and mimic a carburetor fault.
| Check | What to look for | What to do |
|---|---|---|
| Fuel | Stale fuel, wrong mix, or a leak | Replace with fresh, correctly mixed fuel; repair leaks before running |
| Air filter | Dirt or blockage | Clean or replace it as the manual directs |
| Spark plug | Damage, heavy deposits, or a loose cap | Inspect and service it using the manual’s instructions |
| Fuel line and filter | Cracks, leaks, or restricted flow | Stop if damaged; have the fuel system checked |
| Muffler and spark arrestor | Heavy blockage or damage | Clean or service as the manual directs |
| Cutting attachment | Wrong fit, poor tension, or binding | Confirm the approved bar and chain match; correct tension |
Do not pour fuel into the intake or use starting fluid as a shortcut. If the saw still will not start, follow the manual’s starting procedure and have spark and compression tested with suitable tools. Opening the carburetor or guessing at its settings can create new problems.
Next step: Fix any leak or restriction before judging idle speed.
Adjust the LA idle stop, if the manual allows it
The LA screw sets the throttle’s idle stop. It is not a substitute for fixing a fuel, air, ignition, or compression fault. Use this adjustment only if your MS 162 version has an LA screw and its manual gives an adjustment procedure. The stated idle-speed reference is 2,800 rpm, but confirm the specification for your exact saw.
- Put the saw on stable ground outdoors, with the chain clear of anything it could touch.
- Start and warm the engine as the manual directs. Keep two hands on the saw when required by the starting instructions.
- If the manual permits, use a suitable tachometer and follow its LA procedure. Make only the adjustment the manual describes; do not set an assumed wide-open-throttle speed.
- Check that the engine idles reliably and the chain remains still.
If the chain starts moving, stop the engine and do not use the saw. If the engine will not idle without chain movement, stalls when you release the throttle, or races after you let go, stop adjusting and arrange qualified service. Do not compensate by turning H or L screws.
Read the symptom before choosing the next step
A symptom points to a check; it does not prove which part has failed. The table below helps decide whether the approved idle adjustment may apply or whether the saw needs diagnosis. A hanging or unusually fast idle is a stop-work warning, not a reason to keep turning the LA screw.
| Symptom | First checks | Adjustment decision |
|---|---|---|
| Starts, then stalls at idle | Fuel condition, air filter, fuel delivery | Use LA only if the manual allows and the chain stays still |
| Chain moves while idling | LA setting, then carburetor or engine condition | Stop; do not cut until corrected |
| Engine races or idle hangs | Intake leak, fuel delivery, carburetor fault | Stop; do not try to tune it out |
| No start after repeated pulls | Correct start method, fuel, plug, air and exhaust path | Do not adjust the carburetor without evidence |
| Runs poorly under load | Fuel flow, air filter, exhaust, chain condition | Service diagnosis; do not turn H or L screws |
A restricted fuel supply or intake leak can make an engine run too lean, meaning it gets too much air for the fuel available. Lean running can damage or seize the piston. Do not try to cover up a suspected lean condition by enriching the mixture with random screw turns.
Diagnostic examples: when adjustment is not the fix
These are practical examples of how to sort symptoms, not claims about a specific repair or a guaranteed result. They show why I check the simple causes before changing an adjustment. The goal is to make the next step evidence-based, rather than buy a carburetor or guess at a setting.
- It starts, then dies at idle: Check fuel age and mix, air-filter condition, and the manual’s starting steps. If those checks pass, an LA adjustment may be relevant only when the manual permits it.
- It idles, but the chain creeps: Stop the engine. The chain must not move at idle. If the manual’s LA procedure does not correct this safely, seek service.
- It races after the throttle is released: Stop running it. A high or hanging idle can signal a fault beyond the idle-stop setting, including an air or fuel problem.
- It will not start after many pulls: Recheck the cold- or warm-start method and inspect basic items. A carburetor adjustment is not a reliable fix for unknown spark, fuel-delivery, or compression faults.
Next step: If a safe manual adjustment does not restore stable idle with a stationary chain, stop and have the saw checked.
Know when to stop and get service
Service is the safer choice when the MS 162 cannot idle properly, the chain moves at idle, the engine races or hangs at high speed, or it stalls despite correct fuel and basic checks. These signs can point to a fault that an idle-stop adjustment cannot correct. Continuing to run a saw with a suspected lean condition risks major engine damage.
A technician can test fuel delivery, ignition, compression, and possible air leaks rather than replacing parts at random. Ask for the test results and the model-specific service data used. Do not run the saw while waiting for service if it has a fuel leak, unsafe idle, or moving chain.
FAQs
Does the MS 162 have adjustable H and L screws?
Do not treat it as a standard H-and-L tuning platform. Its carburetor is factory-calibrated. Check the exact manual, and do not turn sealed or limited H or L screws.
Which carburetor screw can I adjust?
The LA idle-stop screw may be the only routine user adjustment, if fitted. Follow the procedure in the manual for your exact MS 162 version.
What idle speed should an MS 162 have?
The operating reference given here is 2,800 rpm. Confirm the value for your exact model in its STIHL manual; do not use an assumed maximum no-load speed.
Should the chain move at idle?
No. The chain must remain still while the engine idles. Stop the saw if the chain moves, and do not cut until the problem is corrected.
Can I tune the carburetor by ear?
No. Do not tune by ear or use an unverified RPM target. Use only the manual’s approved LA procedure, if applicable.
What fuel mix does the MS 162 use?
Use a 50:1 mix with STIHL two-stroke oil or oil that meets the specification in the saw’s manual. Do not use straight gasoline or stale, incorrectly mixed fuel.
Why does the saw stall even if the carburetor is set correctly?
A dirty air filter, stale fuel, restricted fuel delivery, a fouled plug, or a blocked exhaust can cause poor running. Check these before suspecting carburetor calibration.
Can I keep cutting if the engine idles high?
No. A high or hanging idle can signal a serious fuel or air problem. Stop the saw and arrange qualified service.
Should I turn the H or L screw if the engine lacks power?
No. Do not turn those screws or defeat limiter parts. Check basic maintenance items, then seek service if the saw still lacks power.
What should I do if adjustment does not fix the idle?
Stop adjusting. If the saw stalls, races, or moves its chain at idle, have the fuel and air systems and engine checked by a qualified service provider.
(This article was written by one of our staff writers, Robert Callahan. Visit our Meet the Team page.)
