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How to start a brush cutter

Cold engine, warm engine, or cordless — starting a brush cutter is easy once you know the sequence. Here's the step-by-step, plus what to do when it won't fire.

By · Updated · first published

In short:To start a cold petrol brush cutter, set the stop switch to on, press the primer bulb until fuel shows, close the choke, pull until the engine coughs, open the choke and pull again; let it idle before cutting. A warm engine starts without choke. Easy-start systems such as Stihl ErgoStart, Husqvarna Smart Start and Stihl's decompression valve make the pull lighter. Cordless machines start at the trigger after the safety lock-off. Stale fuel is the most common reason a petrol machine won't start.

Starting a petrol brush cutter (cold engine)

  1. Fuel and safety. Check there's fresh fuel, place the machine flat on the ground, and make sure the cutting head is clear.
  2. Switch on. Set the on/off switch (stop switch) to the on position.
  3. Prime. If it has a primer bulb, press it 4–6 times until you see fuel.
  4. Choke on. Move the choke to the closed (cold-start) position.
  5. Pull to first fire. Hold the machine down and pull the starter cord firmly 2–4 times until the engine "coughs".
  6. Choke off. Move the choke to the run (open) position.
  7. Pull to start. Pull again — it should start. Let it idle for 20–30 seconds to warm up before cutting.
Tip: machines with an easy-start system (Stihl ErgoStart, Husqvarna Smart Start) need much less effort — the same steps, just a gentler pull.

Starting a warm petrol engine

If the engine is already warm, skip the choke: switch on, prime if needed, leave the choke in the run position, and pull. Forcing the choke on a warm engine floods it.

Starting a cordless brush cutter

  1. Slide in a charged battery until it clicks.
  2. Press the safety lock-off button.
  3. Squeeze the trigger — it runs instantly. Many models have a speed dial for grass vs brush.

When it won't start

  • Stale fuel is the number-one culprit — drain and refill with fresh (or alkylate fuel).
  • Flooded engine (you smell petrol): move choke off, hold full throttle, and pull several times to clear it.
  • Fouled spark plug — clean or replace it.
  • Clogged air filter — clean or replace.

For more, see our maintenance guide.

Four-stroke engines

Four-strokes such as Honda's GX25 and GX35 and Makita's MM4 engines start the same way — primer, choke, pull — but run on unmixed petrol. Check the engine oil level before starting: many four-strokes won't start, or will stop, if the oil is low. Never put two-stroke mix in a four-stroke tank.

Easy-start systems explained

  • Spring-assisted starters (Stihl ErgoStart on the FS 55 C-E and FS 70 C-E) store energy in a spring, so a slow, smooth pull turns the engine over.
  • Decompression valves (Stihl's Easy Start on the FS 131) release compression during the pull, which matters most on bigger engines.
  • Smart Start and fuel pumps (Husqvarna 122C and 128R) reduce pull resistance and prime the carburettor.
  • Automatic chokes (Einhell GC-BC 52) take the guesswork out of the choke position.

Safe starting position

Start on flat, bare ground with the cutting head clear of the ground, grass and your feet. Hold the machine down firmly with your left hand on the housing or handle and pull with your right; never drop-start it in the air. With a blade fitted, make sure the blade guard is on and nobody is within 15 metres. Remove the harness hook while starting if the manual says so.

Quick troubleshooting

  • No sign of firing: stop switch on? Fresh fuel? Spark plug clean and gapped? Try a new plug.
  • Fires then dies: open the choke as soon as it coughs; check the air filter isn't blocked.
  • Runs only on choke: usually a dirty carburettor or old fuel — see runs only on choke.
  • Won't idle: see brush cutter won't idle.

Frequently asked questions

Why won't my petrol brush cutter start?

The most common causes are stale fuel, a flooded engine, a fouled spark plug or a clogged air filter. Start with fresh fuel and a clean plug — that fixes most no-start problems.

How do I start a brush cutter when the engine is warm?

Skip the choke. Set the choke to the run (open) position, prime a couple of times if it has a bulb, and pull — a warm engine usually starts without choke and without full throttle.

How do I start a cordless brush cutter?

Fit a charged battery, release the safety lock-off, then squeeze the trigger. There's no choke or pull cord — it starts instantly.