Should I run my chainsaw dry?

Running your chainsaw dry comes with some risks but there’s another option, that’s simple and inexpensive. You’ll be glad you read this, I promise!

Should I run my chainsaw dry? You should never run your chainsaw dry. You should instead use a quality gas stabiliser. A stabiliser will keep your fuel fresh and protect your fuel system from damage caused by stale gas.

In this guide you’ll learn the risks associated with running your saw dry, you’ll understand what components are at risk and also a fool proof alternative to running your saw dry.

This stuff is all pretty basic, I promise you won’t need a degree in engineering to apply this knowledge.

Empty chainsaw tank

Use a gas stabiliser

Don't run your saw dry

I know plenty of people who run their kit dry when not in use and for most it works out just fine. However running your saw dry can cause the finely balanced and delicate carburettor components to become problematic.

Although the gas has been drained from the tank and the engine ran to a stop. The carburettor components still have a residue, that can cause problems as it drys.

Carburettor parts at risk

Most small engine fuel systems are operated by gravity, lawnmowers, snowblowers, tillers etc. So long as the gas tank is higher than the carburettor, a constant gas flow is available.

Small engine handheld equipment however isn’t always held with the gas tank above the carburettor and so a fuel pump is needed to ensure a constant gas supply.

Your saws fuel pump is a diaphragm, basically a rubber gasket cleverly designed to act like a pump. The pumping action is powered by the rotational movement of the engine, it creates a pulsing vacuum.

The pulsing is what moves the gas from the gas tank to the carburettor, no matter what level the gas tank is positioned.

The fuel supply is proportional to engine speed. More engine speed (revs) equals more fuel supply. A wonderfully clever system.

Chainsaw diaphragm set

Diaphragm

Carburettor Diaphragm gasket

The rubber diaphragm is designed to be flexible, it’s mission critical. The gas and two stroke oil help keep the rubber conditioned. And as you’ve likely guessed, running the fuel system dry, drys out the diaphragm material making it stiff.

You’ll find it difficult to start a chain saw engine with a dry stiff diaphragm gasket, and the only fix is to go ahead and replace it.

If the saw does start you may find it bogs down when working. There are lots of causes of bogging but a diaphragm which isn’t supple enough to move a plentiful supply of gas is high on the list of suspects.

Chainsaw gasket set

Gasket set

Carburettor needle valve

The diaphragm has two important functions, supply’s the gas to the carburettor as you know, but it also helps control the needle valve.

The needle valve meters the amount of gas that reaches the engine. An engine that’s getting too much gas is as ineffective as an engine that’s not getting enough.

The needle has a rubber tip which seals a fuel inlet port inside the carburettor. When the needle tip is in the needle seat (default position) gas can’t flow to the engine.

The diaphragms second function is to press on the needle metering valve arm. The valve arm is a spring loaded lever that pushes the needle into the needle seat (default position).

As the diaphragm pulses, it presses on the lever allowing the needle to lift and gas enter the engine.

So what’s the problem? The needle seal (rubber tip), like the rubber diaphragm is designed to be submerged in gas and oil. Allowing it dry out may cause the needle to stick in the closed position, which as you know blocks gas flow. A pink coloured needle tip means it’s worn.

Carburettor needles

Carburettor Needles

Fixing a sticking Carburettor needle valve

In theory fixing a sticking needle valve is an easy enough problem to solve. The valve simply needs a little nudge to break the seal.

Often just filling the saw with fresh gas, turning it over a few times, leaving it sit for a day or so, it becomes a non problem. If that fails, you’ll need to roll up the sleeves and clean the carburettor (see below).

Carburettor needle

Carburettor Needle valve

Carburettor cleaning

Some carburettors will be easy to access and some will be a total pain in the jacksie. If you’re going to the trouble of removing the carburettor, might as well clean it, replace all gaskets and needle valve.

You can buy a complete repair kit or just replace the whole carburettor, most aren’t that expensive.

Replacing Your carburettor

Although some carburettors may look identical they are calibrated to your engine size. The wrong carburettor will supply too much gas or not enough, so be sure to fit the correct carburettor.

Your old carburettor will have a code cast or stamped into the body, use that code to order your new carburettor.

Some saw manufacturers make their own carburettors but most fit third part carburettors, Walbro and Zama are quality, popular carb manufacturers.

I’ve listed all the most popular ones here together with the tools you’ll need to fit. “Chainsaw parts & tools”

Gas stabiliser

Gas stabiliser

Use a gas stabiliser

My top tip is use a gas stabiliser. It offers the very best protection for your saws fuel system. It removes any risk of gumming which as you know is nasty crap that will cost you a packet to repair.

Stabiliser will keep your gas fresh and protect your carburettor from gumming.

You can use it in all your small engines from lawn mowers to chainsaws, 2 stroke and 4 stroke. It’s not a substitute for two stroke oil, you still mix the oil and gas as per normal.

I’ve listed a gas stabiliser on my “Chainsaw parts & tools” page.

Gas stabiliser

stabiliser

How to use the gas stabiliser

Simply mix the bottle of stabiliser in your refuelling can to the ratio specified. Then mix it with two stroke oil as per your saws user manual.

Your equipment won’t be protected until you run the engine a while to distribute it throughout the fuel system.

Related Questions

How do I winterise my chainsaw?

  • Remove bar and chain
  • Clean sawdust from the saw body, chain and bar
  • Clean air filter
  • Store saw with choke on
  • Fill bar oil reservoir
  • Fill tank with fresh gas, add fuel stabiliser and run engine
  • Spray saw with WD40 
Auto Technician and Writer at | Website

John Cunningham is an Automotive Technician and writer on Lawnmowerfixed.com. I've been a mechanic for over twenty years, I use my knowledge and experience to write "How to" articles that help fellow gear-heads with all aspects of mechanical repairs, from lawn mowers to classic cars.