When a chainsaw starts then dies, the usual culprits are stale fuel, clogged air or spark arrestor, a lean idle, or a failing spark plug.
What This Guide Delivers
You’ll get a simple flow that finds the stall, clear steps that take minutes, and safe ways to test without guessing. No fluff, just fixes that work in a yard or on a job.
Chainsaw Not Staying Running: Quick Checks
Before you grab a screwdriver, confirm the basics. Fresh mix, clean air, sharp chain, and correct tension all affect idle and throttle. A saw that fights the cut or loads the clutch will bog and quit.
Fast Symptom Map
Match what you hear and see to a likely cause, then jump to the fix. Use this first table to save time.
| Symptom | What It Points To | Quick Check |
|---|---|---|
| Starts then dies at idle | Lean idle, clogged air filter, or fouled plug | Warm saw, raise idle a touch; clean filter; inspect plug |
| Bogs with throttle | Dirty spark arrestor or plugged fuel filter | Brush screen; pull fuel filter and check flow |
| Dies when tipped | Cracked fuel line or loose pickup | Shine light in tank; flex lines for splits |
| Surges, hunts, won’t settle | Air leak at carb boot or crank seals | Spray soapy water near joints; note idle change |
| Only runs on choke | Carb jets gummed by old gas | Drain and clean; run fresh mix through |
| Chain creeps at idle | Idle set high or clutch sticking | Back idle screw off; check clutch shoes |
Start With Fuel, Air, And Spark
Most stalls trace to one of these. Work clean, away from flame. Use premix or mix fresh 50:1 two-stroke fuel and store small batches. If your saw sat on E10 for months, swap it out. Ethanol can pull in water and leave varnish that starves a tiny jet.
Need a reference on mix and containers? See the official STIHL 50:1 mixing guide for ratios and fueling tips. For a brand page that lists common “starts then dies” causes with fixes, check Husqvarna’s help article on why a chainsaw starts and then stops.
Fuel System Refresh
Drain the tank and purge the line. Pop the fuel filter and replace if flow is weak or the felt looks dark. Refill with fresh mix. Prime until the bulb returns fuel cleanly. If the saw only runs with the choke, varnish is likely. A small dose of carb cleaner in the throat can confirm the direction, but a proper clean means removing the carb and washing the metering parts.
Air Filter And Spark Arrestor
Wash a foam filter in warm soapy water and dry. Tap a felt filter to knock dust out, or swap it. A packed spark arrestor screen chokes the exhaust and causes a stall when throttled. Brush the screen with a brass brush or heat it off the muffler and burn the soot out, then reinstall.
Spark Plug Check
Pull the boot, remove the plug, and read it. Dry tan is healthy. Wet and black means rich or flooded. Gap it to spec, clean or replace. While the plug is out, ground it to the case and crank—look for a snappy blue spark.
Idle And Mixture: The Three Screws
Your carb has three adjusters on most pro saws. L sets off-idle mix, H sets top-end mix, and LA (or T) sets idle speed. A saw that runs then quits at idle often needs a small bump on LA after the engine is warm.
Safe Idle Set
Warm the saw ten minutes. Turn the LA or T screw clockwise in tiny steps until the chain almost wants to move, then back it off until the chain stops. Snap the throttle. The engine should pick up cleanly and settle without dying.
Cleaning Up Off-Idle
If it stumbles right when you touch the trigger, turn the L screw clockwise in a small step to lean the mix, test, then fine-tune back if the idle hangs. If it sags as you rev and recovers slowly, add a touch counterclockwise on L. Make changes in eighth turns and retest.
Top-End Caution
H affects power and heat. If you lack a tach and a model spec, don’t chase top-end on guesswork. A safe sign is a crisp four-stroke burble at full throttle that cleans under load. If you hear a dry, high pitch at wide open, that’s lean—back off.
Mechanical Load That Causes Stalls
Not every stall is fuel or spark. Extra drag can pull rpm down until the clutch lets go. Fixing that load can make the tune fall into place.
Chain Tension And Bar Oil
Set tension so the drive links just kiss the bar groove and the chain still pulls by hand with gloves. Oil flow should leave a faint line on fresh wood. Dry rails or a blue chain means heat and drag.
Clutch, Sprocket, And Brake
A dragging chain brake band, a worn rim sprocket, or clutch shoes that stick can stall a small engine at idle. Spin the drum by hand with the brake off. If it drags, service the brake cover, clean chips, and inspect the band. Replace a hooked rim.
Intake Leaks
Torn intake boots and loose carb mounts let unmetered air in. That creates a lean mix that dies at idle and races when you blip the trigger. Look for splits, loose clamps, or fuel staining at joints.
Step-By-Step Fix Plan
Work from easy to deep. The order below catches nine out of ten stalls in ordinary use.
1) Replace Old Fuel
Dump the tank, fit a new filter, and fill with fresh 50:1. If the saw sat all season, run a premixed alkylate can for a tank to clean light gum.
2) Clean Air Path
Service the filter, clear the spark arrestor, and confirm the muffler outlet is open. Re-test idle and throttle. Many “dies at idle” issues stop here.
3) Set Idle Warm
With a hot engine, tweak the LA or T screw so the chain rests but the motor doesn’t cough out. Snap the trigger and watch for clean return to idle.
4) Tidy The L Circuit
Adjust the L screw in tiny moves until tip-in is smooth. Always return to idle and confirm the chain is still still.
5) Inspect Lines And Vent
Cracked fuel lines suck air. A stuck tank vent will starve the carb and kill the saw after a minute. Loosen the cap and see if it now keeps running. If yes, replace the vent.
6) Deep Clean The Carb
If nothing sticks, remove the carb, note screw positions, and strip the float bowl and metering cover. Clean jets with carb spray and a soft tag wire. Fit a kit if the diaphragm is stiff or creased.
Specs And Targets You Can Use
These are typical values and checks for many two-stroke saws. Always follow your model’s card if you have it.
| Item | Target Or Tip | Why It Matters |
|---|---|---|
| Fuel mix | 50:1 with fresh, name-brand oil | Correct oiling keeps heat in check |
| Idle speed | Set so chain is still, engine steady | Stops clutch drag stalls |
| Air filter | Clean often; replace when torn | Airflow keeps tune predictable |
| Spark plug | Dry tan, correct gap, snug crush | Strong spark holds idle |
| Arrestor screen | Brush clean; no heavy soot | Exhaust flow supports throttle |
| Fuel age | Use within 60 days | Old fuel gums tiny jets |
Safe Test Habits
Wear eye, ear, and leg protection, set the brake when starting, and never drop start. Test cuts with clear footing and no one near the bar tip. A steady setup helps you hear small changes in the tune.
When The Saw Still Quits
If you’ve set idle, cleaned filters, and fitted a new plug and it still fades out, you may have low compression or a crank seal leak. That calls for a pressure and vac test and a cylinder peek. Shops can do this fast with the right tools.
Keep It From Coming Back
Fuel And Storage
Mix small batches, label the can, and cap tight. Run the saw dry for storage or use canned alkylate fuel. Store the saw empty in a cool, dry spot. These small steps keep jets clean and diaphragms fresh.
Cutting Habits
Keep a sharp chain and let the saw rev before the cut. Don’t force the bar. Clearing chips, oiling well, and easing the nose out of pinches saves rpm and keeps a tune stable.
Quick Prep List Before Work
Top the tank, check chain tension, test brake, tap the filter clean, and crack the cap to be sure the vent isn’t stuck. A two-minute prep prevents a mid-cut stall.