Chainsaw Won't Start? 6 Fixes in the Order to Try Them
Lawn Tool Hub is reader-supported. We earn a commission from qualifying purchases made through links on this page, at no extra cost to you. Learn more.
The short answer
Work the list in order: (1) fresh mixed fuel, (2) spark plug, (3) air filter, (4) flood clear, (5) carburetor adjustment, (6) fuel filter and lines. About 80% of no-starts end at steps 1 – 3, and most of those are stale fuel from last season. If it starts, runs, and dies when you give it gas, that is a carb low-speed jet or fuel-delivery problem, not spark.
STA-BIL Fuel Stabilizer
Stabilized fuel survives the off-season; stale fuel is next spring's no-start. Run it through the carb before storage.
A gas chainsaw that refuses to start after a winter in the shed is not broken — it is usually pickled. Old two-stroke mix turns to varnish, the fuel line hardens, and the plug fouls from all the failed starting attempts. Before you diagnose anything else, put fresh 50:1 mix in it. Half the time that is the whole fix.
The Order to Try Things
- 1Fresh fuel, correctly mixed. Dump the old mix — do not top it off. Gas starts degrading in 30 days, and two-stroke mix degrades faster. If the saw sat all winter with fuel in it, drain the tank and the carb bowl if you can.
- 2Spark plug. Pull it, check the electrode for oil fouling or cracking, gap it to spec (usually 0.020 in) or just replace it — plugs cost a few dollars. A wet plug after failed starts means flooding, not a bad plug.
- 3Air filter. A foam or felt filter clogged with sawdust chokes the engine. Wash foam filters in warm soapy water, dry fully, lightly oil if the manual says so. Replace felt filters.
- 4Clear a flood. Choke on, plug out, pull the starter 5 – 6 times with the plug hole facing down. Dry the plug, choke off, full throttle lockout, and pull until it catches.
- 5Carburetor adjustment. If it starts, idles, then dies when you throttle up, turn the low-speed (L) screw out an eighth turn at a time. If it runs at speed but won't idle, adjust the idle screw up slightly.
- 6Fuel filter and lines. The in-tank filter hangs on a pickup line and clogs with varnish. Fish it out with a wire hook, replace it, and squeeze-test the lines — if they crack instead of flex, replace them.
Myth
If it won't start, the carburetor is shot and needs rebuilding.
The Fact
Carb rebuilds are the last resort, not the first. Stale fuel, a fouled plug and a clogged filter account for the overwhelming majority of no-starts and take ten minutes to rule out.
Parts Worth Having on the Shelf
STA-BIL Fuel Stabilizer
The cheapest insurance in small-engine ownership. Stabilized fuel lasts through the off-season; unstabilized fuel turns to varnish and creates next spring's no-start. Run the treated mix for a few minutes at the end of the season so it reaches the carb.
Carburetor Adjustment Tool
Most modern saws use splined or special-head screws specifically so homeowners can't tamper with emissions settings. The right tool costs about $10 and turns a factory-set carb from untouchable to tunable.
Spark Plug for Your Model
Check the manual for the exact plug (many small saws share the CMR6 family). Buy two: one on the shelf means a fouled plug is a five-minute fix instead of a trip to the dealer.
Frequently Asked Questions
- The saw starts and immediately dies. What is it?
- Fuel delivery almost every time: clogged in-tank filter, cracked fuel line, or a carb low-speed jet varnished shut. Fresh gas through a cleaned system usually fixes it.
- How do I store a gas chainsaw so it starts next season?
- Either run the carb dry and store it empty, or fill with stabilized fresh mix and run it briefly. Both work; the middle ground — old fuel sitting in the tank — is what causes no-starts.
- Can I use car gas without oil mix in an emergency?
- No. Two-stroke saws need oil mixed into the fuel. Straight gas even briefly can score the piston. Four-mix engines (like some Stihl and Honda units) are the exception — check your manual.
The Gear We’d Buy
Everything referenced in this guide, in one place.
STA-BIL Fuel Stabilizer
PreventionStabilized fuel survives the off-season; stale fuel is next spring's no-start. Run it through the carb before storage.
Typically $10 – $20
Carburetor Adjustment Tool
DiagnosticModern saws lock the tuning screws behind special heads. Ten dollars turns a factory-set carb from untouchable to tunable.
Typically $8 – $15
Spark Plug for Your Model
Fouled plugs cause more phantom faults than any other part. Buy two and keep one on the shelf.
Typically $4 – $10
Lawn Tool Hub is reader-supported. We earn a commission from qualifying purchases made through links on this page, at no extra cost to you. Learn more.
Key Takeaways
- Fresh 50:1 mix fixes most no-starts before any diagnosis.
- Then spark plug, air filter, flood clear, carb, fuel filter — in that order.
- Runs-then-dies means fuel delivery; won't-fire-at-all means fuel or spark.
- Stabilize fuel at season's end and next spring starts on the first or second pull.
Reviewed by
The Lawn Tool Hub Test Bench
We buy, borrow and break lawn tools on our own yards — clay in the back, sand-cut Bermuda in the front — and write down what actually changed the result.
Keep reading
The Best Cordless Chainsaw for Suburban Yard Work
Battery chainsaws sized for real yard work: limbing, storm cleanup and small fells. We compare runtime, bar length, chain speed and which battery platform is worth buying into.
Mini Chainsaw vs Full-Size: Which One Actually Earns Its Spot
6-inch mini chainsaws are everywhere. We compare them against a real 12 – 16 inch cordless saw for pruning, storm cleanup and safety, and name who should actually own which.
How to Sharpen a Chainsaw Chain with a File (and When to Replace It)
Sharpen a chainsaw chain by hand with the right round file, the right angle and consistent strokes. Includes the file size for your chain pitch, the 5-second dullness test and when a chain is past sharpening.
Prevention
STA-BIL Fuel Stabilizer