You pull the cord, and nothing. Then again, and again, until your shoulder complains. It’s a frustrating way to start a day’s cutting, but the good news is that most chainsaw faults fall into a small handful of causes. Working through them in order tells you whether it’s a two-minute fix or a job for our workshop, and our chainsaw repairs team runs through the same checks every week.
A two-stroke engine runs on fuel, spark and compression. If it won’t fire, one of those three is missing, and diagnosing in that order stops you from replacing parts at random.
Start with the obvious, because the obvious is right surprisingly often. Is there fuel in the tank? Is the chain brake off? Is the stop switch in the run position? Plenty of saws arrive on our bench perfectly healthy, just switched off.
Old petrol causes more no-start faults than anything else. Mixed two-stroke fuel degrades within weeks, leaving a sticky residue that clogs jets and gums the carburettor.
Work through these checks:
If fresh fuel gets it running roughly, the carburettor probably needs cleaning and rebalancing. That’s fiddly work and easy to make worse, so it’s usually worth passing over.
Pull the plug and read it. Light tan means the mixture is about right. Black and oily suggests it’s running rich or the air filter is choked. Wet with petrol means it has flooded, so leave the plug out and pull the cord to clear the cylinder.
Spark plugs are cheap, and they do wear. If the electrode looks eroded or the gap has opened, fit a new one before chasing anything complicated. When a fresh plug still gives no spark, the ignition coil or kill switch wiring is the likely suspect, which needs proper testing.
Compression is the one you can’t bodge. If the cord feels loose and easy to pull, the piston rings or cylinder may be worn or scored. That often follows a run on the wrong fuel mix, or long use with a starved air filter. Don’t keep yanking at it, either. Running a saw with poor compression can turn a rebuild into a write-off, so bring it in and we’ll measure it first.
Sometimes the saw runs fine, and the problem is everywhere else. A blunt chain forces you to lean on the bar, which overheats the engine. A loose chain throws off the bar, and worn drive sprockets chew through new chains quickly.
Check the bar rails for uneven wear and clear the oil hole while you’re there. If the chain isn’t lubricated, everything wears fast. A sharp chain and clean air filter prevent most of the repairs we see, and lighter jobs are often easier on a battery saw from the EGO Power+ range.
How often should a chainsaw be serviced?
Once a year for occasional home use, or every few months if you’re cutting most weeks.
Why does my chainsaw start then cut out?
That usually points to fuel supply: a blocked filter, a perished line, stale petrol or a blocked tank vent.
How long does stored petrol stay usable?
Treat mixed two-stroke fuel as good for around a month.
Is it worth repairing an older chainsaw?
Often yes. Quality saws are built to be rebuilt, and the common parts are inexpensive.
If fresh fuel, a new plug and a sharp chain haven’t solved it, the fault is deeper. Our mechanics have spent over a decade repairing saws for arborists and homeowners across Carmarthenshire, work that earned us a feature in PROARB magazine. We’ll tell you what’s wrong, what it costs and whether it’s worth doing. Contact our workshop to book your saw in, or call into the showroom.
