STIHL Chainsaw Won't Start? The Parts We Replace Most (After Sitting or When Hot)

Chainsaws are the second-busiest family in our repair records — almost 900 parts installed on saw repairs. On STIHL saws, the parts we replace most are air filters, spark plugs, fuel filler caps and carburetors. Here's how to narrow down which one your saw needs.

Quick reference

STIHL chainsaw won't start after sitting

This is the classic. Fuel left in the saw over a few months evaporates and leaves varnish in the carburetor and stiffens the fuel line.

1. Dump the old fuel. Refill with fresh 2-stroke mix made with STIHL HP $18.46 or HP Ultra $22.76 oil.
2. Check the fuel line inside the tank — if it's hard or cracked, replace it (for example the MS 210/230/250 fuel hose $17.39 or MS 260 fuel hose $9.78).
3. Replace the fuel pickup filter if it's dark or clogged.
4. If it still won't run right, the carburetor needs a rebuild or replacement. The C1Q-S76D carburetor for MS 230/250 $41.30 is one of the carbs we install most (19 repair orders).

Floods, hard starting or won't fire

Pull the plug. A wet plug means flooding — set the switch to run, open throttle, pull until it fires to clear it. A fouled or worn plug should simply be replaced: the NGK CMR6H $14.96 and NGK BPMR7A $10.94 are the plugs we install most on STIHL saws, depending on model.

Then the air filter. STIHL's 1141 140 4400 $16.52 and the flocked filter for MS 210/230/250 $9.77 are the two most-replaced parts on chainsaws in our records (38 and 34 repair orders). A dirty filter makes the saw rich, hard to start and weak.

Leaks fuel, won't hold prime

STIHL's tool-less fuel caps have a seal that wears and lets air in or fuel out. Fuel filler caps (0000 350 0533 $9.78, 0000 350 0537 $8.69) appear on 19 repair orders each from our service department's repair records. If the cap won't lock or you smell fuel, replace it.

STIHL chainsaw won't start when hot

If it starts cold but won't restart hot, check for a too-rich mixture from a clogged air filter first, then vapor lock from a soft fuel line near the cylinder. If both are good, an ignition module breaking down with heat is the next suspect — that's worth a shop diagnosis.

Won't stay running or won't idle

Usually a clogged idle circuit in the carburetor, an air leak (cracked intake boot or fuel line), or idle speed knocked out of adjustment. A rebuild or the correct replacement carb for your model is the usual fix.

While it's apart

Sharpen or replace the chain — STIHL 36RS 3/8" .063 chain is the chain we install most — and check the bar rails and sprocket.

STIHL starting procedure (it matters)

Many "won't start" saws are just flooded from a wrong starting sequence. Use the master control positions in your manual: cold start (choke), pull until it pops, move to the half-throttle/warm position and pull until it runs. Repeatedly pulling on full choke after it has popped floods the cylinder.

Fuel tips that prevent most saw repairs

• Mix only what you'll use in a few weeks.
• Use quality 2-stroke oil at the ratio on the bottle.
• Empty the tank before long storage.

Parts in this guide

AIR Filter$16.52AIR Filter-flocked MS 210230250021023025$9.77CMR6H-3365-SLDNGK$14.96BPMR7A NGK Spark Plug$10.94Filler Cap$9.78Carburetor C1Q-S76D MS 230/250$41.30Fuel Hose MS 210230250021023025$17.39Stihl HP 5.2 OZ 2 Cycle Engine Oil 6 Pack$18.46

FAQ

Why won't my STIHL chainsaw start after sitting?

Old fuel has varnished the carburetor or hardened the fuel line. Replace the fuel, fuel line and pickup filter; rebuild or replace the carburetor if needed.

What spark plug does a STIHL chainsaw use?

It depends on the model; NGK CMR6H and BPMR7A are the plugs we install most on STIHL saws.

Why won't my STIHL chainsaw start when hot?

Check for a clogged air filter (too rich), a soft fuel line near the cylinder (vapor lock), then the ignition module.

Related guides

• STIHL Chainsaw Chain Cross Reference (Pitch, Gauge & Links)
• Zero Turn Won't Start? Causes Ranked by Real Repair Data (and the Parts That Fix Them)
• Zero Turn Won't Move or Go Forward: Belts, Idlers & Hydro Fixes
• Lawn Mower Runs Then Dies? Fix the Fuel System in This Order
• STIHL TS 420 Parts: Spark Plug, Air Filter Kit & Wear Parts

Repair statistics in this guide are aggregated from our service department's repair records. Part numbers come from manufacturer parts lists; always confirm fitment with your model and serial number.