Here’s TUAK’s very first (and possibly last) how-to essay. If you already know how to use and maintain a chainsaw, or if you just don’t have one, proceed no further because this is rather long.
If you do own one and are feeling a bit uncertain on some related matters, click away.
BTW, if you do take the time to read this for information and find it inadequate, please leave a comment as to how it could have been improved. When writing a piece like this it’s very easy to make assumptions about what readers do and don’t already know. Y’know?
The thing to remember about a chainsaw, in terms of its maintenance, is that any time you’re using it you’re beating the hell out of it. A good saw will give you years of good, trouble-free service just like any tool. But that’s only if you treat it right. You just can’t ignore maintenance and expect it to keep running, because a little abuse and neglect goes a long way.
Consider the engine, for example.
That tiny little single-cylinder, two-stroke sucker can only do its thing under full-throttle, at which it’s cranking something like 13,000 RPM. The frictional loads it has to deal with are enormous (more on them later.) It has no liquid coolant, no bath of crankcase oil, and it will drag six feet of sharpened chain links through hard, seasoned wood all day long. Or not, depending on whether you do your part.
So let’s go through the parts of the chainsaw, and what care it needs to keep running right.
This is the drive sprocket, which is where the chain meets the saw. Depending on the brand of the saw the sprocket can take different forms, but they all do the same thing. The sprocket links with the drive tabs on the chain and sends it whipping around the bar at lethally high speed.
This is the bar. The chain’s drive tabs run in grooves on the top and bottom of the bar, and run through a sprocket on the front end. All the force exerted on the chain causes wear on the bottom side of the bar, which is why most chainsaw bars are reversible – you can mount it with either side down. By the end of a long winter, you’ll be happy for that.
Some bars use a “hard nose” design, which eliminates the bar sprocket. They’re more expensive, but get rid of a moving part that’s a common failure point. If you keep the sprocket clean and greased, though, it’s rarely a problem.
This is the chain tension adjuster. Again, it looks different on different saws but they all do the same thing. More on chain tension later.
This is the air filter. On your car, you’re probably used to not giving your air filter much thought but that won’t work well on a chainsaw. The saw works in an incredibly dirty environment, and the filter is a simple screen. It gets dirty very fast, and needs cleaning often. The simplest and best way to clean the filter is to spray it out with air pressure.
That complicated-looking black thing in front of the upper handle is the actuator for the chain brake. If the chain hangs up in a piece of work, the saw will kick back toward you and that’s never a good thing.
The idea is that your hand will slip off the upper handle and bump the brake actuator. If that black actuator gets bumped it will click forward and lock a brake band around a drum, preventing the drive sprocket from rotating. It’s kind of a complicated mechanism, but when it’s working right that will make the chain stop moving right away.
That’s fine, but there are issues. If you ever try to rotate the chain on the bar and it won’t move, check the chain brake actuator first. Just try to move it toward the rear of the saw. If it moves backward with a solid click, you just fixed the problem.
Also, and this is very important: On Husqvarna saws, the brake band is mounted right on the inside of the sprocket cover. If the brake is actuated, it will be impossible to remove the cover without using force. I can’t tell you how many saws I’ve repaired where people went ahead and applied that force. DON’T DO THAT. On a Husky saw, if you can’t get the cover off the very first thing you should check is whether the chain brake is applied. If it is, turn it off and the cover will come right off.
I don’t know if any other brands use this design. The only one I’ve seen is Husqvarna. But if you’re having trouble getting the cover to want to come off, don’t force it. Check the chain brake.
This is the bar oil reservoir. Friction between the chain and the bar produces a lot of heat, and you will tear up both if you don’t keep them lubricated. All modern chainsaws have automatic oilers so you don’t have to give bar lubrication much thought as long as the oiler is working, but you do want to keep sure that it is working. If you’re ever not sure, just aim the end of the bar at an uncluttered patch of ground while the saw is running and hit the throttle. At full speed, the chain should lay a line of oil on the ground. If it doesn’t, stop cutting till you find out the problem.
As you can imagine, all that centrifugal force wants to send oil flying everywhere. That’s why bar oil is specially formulated to be extra sticky compared to motor oil. It’s more expensive, but this isn’t a place to save pennies because bars and chains are even more expensive. Much more. Make sure you keep oil in the reservoir.
This is where the mixed fuel goes.
Remember that the chainsaw’s engine has no crankcase. It’s lubricated through the fuel. You must not ever run straight gasoline in a chainsaw. So you’ll need a dedicated fuel container and a supply of mix oil. Mix your fuel according to the instructions on the oil bottle. When in doubt, too much oil is better than too little. Too much will cause your engine to run a little smoky and possibly, eventually, clog the spark arrester on the muffler. Too little will cause your engine to seize, and convert your expensive saw into an unusually dirty paper weight.
And of course this is the chain. The chain must be sized correctly for the saw and bar, and the cutting links must be kept sharp. If you find the saw reluctant to cut, or if the chain starts trying to burn its way through wood, the chain is dull and must be sharpened.
We could do a whole article on just this one part: Different sizes and types of chains, how to size them, how to sharpen them. We don’t have space for any of that. When in doubt, consult your dealer. But I will say one thing here about dull chains. When you cut with a dull chain, you’re doing more than burning wood and tearing up cutting links. In order to cut with a dull chain, you need to bear down on the saw, right? When you do that, you’re taking months of life not just off the chain, but also off the bar, the drive sprocket, and the engine. Think of that burning smell you detect as being the smell of burning money, and then stop cutting until you can sharpen the chain. Most serious chainsaw users keep several chains around. They’re easy to swap out.
Okay, let’s get to work!
To mount the chain, orient the chain so the cutting blades on the top of the chain face toward the front of the saw. NOTE: It is possible to mount the chain backward. This doesn’t really hurt anything, but the saw won’t cut. To repeat: the cutting blades on the top of the chain should face the front of the saw.
Now wrap it around the drive sprocket, making sure the drive tabs mate with the slots in the sprocket.
Now put the bar in place on the bar studs. Push it all the way to the rear at first, and don’t worry about connecting it with the tensioner. Drape the chain on the bar so it engages with the upper slot and the bar sprocket. The bottom part of the chain should hang down loose.
Now gently pull the bar forward, and engage it with the stud of the tension adjuster. On some saws, the adjuster is on the sprocket cover so you’ll need to install the cover for this step. If you run out of chain before you can get the stud through the hole in the bar, back off the adjuster by turning it counterclockwise. At this point, the chain should still be quite loose.
If you haven’t already, go ahead and mount the sprocket cover now. Don’t tighten the nuts, because we still need to adjust the chain tension.
Pull up gently on the chain. If the drive tabs come out of the bar groove, the chain is too loose. So rotate the chain tension adjuster clockwise, which will move the bar outward and tighten the chain. Do this gently: You don’t want the chain too tight.
When gently pulling on the chain causes the drive tabs to come up off the bar but not all the way out of the groove, you’re about right. Now rotate the chain on the bar. It should move freely.
If it doesn’t, check the chain brake. If the chain brake is not actuated, you’ve done something wrong. Back up and find the problem. Don’t try to use the saw unless the chain is rotating freely on the bar.
Starting the Saw
All set? Okay! Having checked your fuel, bar oil and chain tension, it’s time to fire this bad boy up. Starting a cold chainsaw engine comes in two stages. Do it right, and we’ll have you going in no time. Screw it up, and you’ll flood the engine. You don’t want to do that.
Make sure the chain brake is OFF.
Push the power switch to the ON position. Pull out the choke lever. Leave the throttle alone. Hold the saw down with one hand, and pull the starter cord sharply with the other. After two or three pulls, the engine should start and immediately die. That’s fine, that’s just what it’s supposed to do. You just properly primed the fuel system.
NOTE: Some chainsaws have primer bulbs to help this process along. I dislike this feature a great deal because they don’t really help things, they make it easy to flood the engine without ever pulling the starter cord, and they’re a common failure point. But if you’ve got one, you’ve got one. Read and follow the directions carefully.
Open the choke. On some models you can do this by flicking the throttle trigger. On others, you need to push the choke lever in. Hold the saw down with one hand, and pull the starter cord sharply with the other. After two or three pulls, the engine should start and keep running.
Individual chainsaws develop personalities. Some saws like a little throttle to get started at this stage, but it should still idle with your finger off the trigger. If you must give the engine some throttle, be mindful of where the bar and chain are. If you goose the throttle, the chain will spin. That can ruin your whole day if you’re not ready for it.
That’s almost it! You’ve got a running chainsaw in your hands, so you really shouldn’t be reading this right this minute. Just a few more words:
First: If you have trouble starting the saw, you’re running the risk of flooding the engine. If you can’t start the engine and you start smelling gasoline, stop immediately. You flooded it. Remove the top cover, remove the spark plug, and note that the electrodes are all covered with liquid fuel. The engine will never start once that happens. Dry the plug electrodes carefully. Then before re-installing the plug, pull the starter several times to run air through the cylinder and try to get any liquid fuel out of there. Re-install the plug and cover and go back to Step 1.
While you’re using the saw, periodically stop the saw to check and adjust the chain tension. Chains stretch. A chain that’s too loose will come right off the bar. It will damage the chain and may damage you.
I have actually met someone who tried to adjust the chain tension while the engine was running. Only the one guy, though, because almost everybody is smarter than that.
A Word About Spark Arresters
At the outlet of the muffler, you will find a little removable screen. That’s the spark arrester, and it does just what the name implies.
Sometimes at the shop we got customers who complained that they could start their saw easily enough but it wouldn’t develop any RPMs or power. Most often, the fix for this was very simple. Remove the small screw(s) holding the arrester screen in place, and pull it out with small pliers. If the screen is clear, that’s not your problem. But often you’ll find that the screen is clogged. This is caused by too much oil in the fuel mix. It doesn’t do any serious harm, but the engine won’t run right until you clean the screen.
That goop is burned on. The best way I’ve found to clean it is to heat it red-hot with a propane torch, then scrape it clean with a wire brush or screwdriver.
A Word About Cleanliness
A chainsaw works in a terribly dirty environment, and it will get terribly dirty. Some parts need to kept reasonably clean or they won’t work right. Most of this is common sense. The air filter, for example: You should clean it after every session. The engine draws a great deal of air through a tiny carburetor inlet, and you’ll be surprised how fast the filter can clog. NEVER EVER RUN THE ENGINE WITHOUT A GOOD FILTER.
On my older Husky 55 the chain tension adjustment point is between the saw and the bar, a dumb design they changed on the newer models. Dirt just packs in there, and I have to scrape it out several times a session. You get used to it.
Obviously, you need to clean all around the bar, chain and drive sprocket inside the sprocket cover. Dirt and sawdust mixes with bar oil at this point and it doesn’t just drift in, it’s apparently packed in under great pressure. Keeping this area completely clean requires a level of OCD your humble writer does not possess. But at a minimum you do need to keep it from packing up so deep that it starts impeding moving parts, okay?
At the point where the bar is pinched against the saw, there’s a little slot where the bar oil comes out to lube the bar and chain. Check this any time you have the bar off, to make sure it isn’t getting clogged with dirt. That’s a common way for the automatic bar oiler to fail.
Make sure dirt and sawdust doesn’t start packing between the heat sink fins on the engine’s cylinder head. It’s an air-cooled engine, which means air has to be able to get in there. Packed crud in there can ruin the engine forever.
Don’t forget the starter mechanism, on the opposite side of the saw from the sprocket cover. From time to time, remove the starter and make sure dirt, sawdust and twigs aren’t getting involved with the starter cord. Most designs have a couple of centrifugally-actuated levers that can become too dirty to do their trick: Make sure they remain free on their springs. Also, from time to time pull out the cord all the way and make sure it isn’t fraying. A frayed cord should be replaced as soon as possible because they do break. When it breaks, there’s no more saw for you.
Do I really need to tell you that you shouldn’t leave your chainsaw outdoors? Yet people do, and suffer the consequences, and the main reason is that automatic oiler. The big problem with chainsaw storage is that they tend to leak oil at all times, and bar oil is insidious stuff. Like I said earlier, it’s stickier than regular oil and harder to clean out of other materials.
Get your chainsaw its own container. You will thank yourself for this. Regular chainsaw cases, though expensive, are a very good investment in chainsaw longevity. Personally, I use a big Rubbermaid tub in which I store the saw and all its tools, spares and materials like bar oil, mix oil, and fuel. That way, in addition to keeping it out of the weather and ensuring it doesn’t make a mess, I always know where all the other bits are.
Leave it in the sun, or just leave it laying around for a few months, and gasoline goes bad. Not being a chemist, I can’t tell you why this is and don’t care. All I know is two things: Bad gas smells really foul, and it’s death to chainsaws.
Chainsaws use diaphragm-type carburetors, which are extremely sensitive to bad gas. Bad gas attacks the diaphragms, turning them stiff and brittle and incapable of doing their thing. It can also do other bad things to your saw, but that’s the most common and it’s a show-stopper. A good shop can get you running again, but it’s really best to prevent the problem.
Two rules, which you break at your peril:
1.Always check your fuel by smell before pouring it into your saw.
2.Never store a saw long-term with fuel in it.
When you’re getting ready to store your saw, empty the fuel tank. Then start the engine and run it until it dies for lack of fuel. It won’t hurt anything, but leaving the fuel in there might.
For gasoline that’s going to be around for a while, go to an auto parts store and get yourself a bottle of fuel stabilizer. Then use it faithfully. You will look so much smarter if you do this.
Speaking of Spares…
Here’s a list of things I always keep on hand, to make sure I can cut wood any time I want to:
Chains: I like to have at least five on hand, but I heat with shaggy-bark Juniper which is as chainsaw-unfriendly a wood as exists anywhere. You should have at least two or three chains.
Air filter: Not essential, but removes the temptation of continuing work with a damaged or over-clogged filter.
Starter cord: Believe me. Sooner or later you’ll want this.
Mix oil, obviously
Bar oil. If you find yourself completely without bar oil, clean motor oil is better than nothing but it doesn’t work as well. You shouldn’t use substitutes here. Also, I’ve met some people who think this is a good place to recycle dirty used motor oil. They’re wrong.
As for tools, the only tool not associated with chain sharpening you really need is a flat-blade screw driver and two sockets, one for the bar nuts and one for the spark plug. The screwdriver will do double duty for scraping out the worst of the built-up crud. If you buy your saw new it will probably come with a gadget called a “Scrench,” which has all three tools built into one.
That’s all I can think of right now. If you read this and found a question unanswered, please leave your question in the comments because I’m trying to make this as complete as possible without making it 10,000 words long.
Thanks for reading! Let’s be careful out there.