Stihl 025 Piston 1123 030 2002

Part description: Stihl 1123 030 2002 piston

Replacement 42mm piston, rings, pin and clips for Stihl 025 chainsaw model.

42mm diameter

Uses Stihl 1123 034 3003 42mm piston rings.

Other part numbers:
11230302002

All right folks, we're doing another video today. We’ve got a Stihl 025 chainsaw that does not run. Stick around.

All right, here's the deal. I was cutting a tree down with this bad boy, not one lick of trouble. Started cleaning up the branches, not one lick of trouble. All of a sudden it started running worse and worse, and then I could hardly keep it running. When I was cutting, it was bogging down real bad, and finally it got to the point where it wouldn't run at all.

So I'll show you what the problem is. We're going to take the thing all the way apart, but first we'll start by taking the muffler off because that's where the problem can be seen. I'll show you what it is.

I've had this problem before on this chainsaw, and it doesn't say anything bad about the chainsaw because this chainsaw went for about twenty years without ever having a problem. I think the problem is the gas I've been mixing for it because all of a sudden I've had this happen twice, and my blower once. I kind of blamed the blower when it happened, but now that this is the third time, I believe the problem is my gas.

If you look inside this hole for the exhaust, you can see that the piston is badly scored, and the rings are as well. That's the problem.

What I believe happened is that I was not using good enough oil in the gas mix, and as a result it prematurely wore out these cylinders, pistons, and rings. After I do this repair, I am going to buy some higher-quality two-cycle oil and double-check my mixing method.

Like I said, for years I never had an issue and I always used the Stihl two-cycle oil. Lately I haven't been using it. In the last few years I've been buying the cheap stuff, and I'm pretty sure that's why I'm having issues here.

So we're just going to pop that fuel line off. We're going to pop this linkage off by simply pulling it out like so, and we're going to pop the throttle linkage off by simply popping that out like so.

Now we can pull the carburetor off. I have had the carb off and cleaned it thoroughly, and this thing is crystal clear, so that isn't the problem. I already showed you the problem. I don't know why I'm even telling you what the problem isn't.

Anyhow, here's a little pro tip. I get a little clamp like this and stick it on the fuel line to clamp it off because we're going to be turning this thing upside down, and I don't want gas spilling all over.

We'll take the blade off and get it out of the way. Once I fixed this the first time, it ran fantastic for a little while. It was one tree's worth of cutting. It was a big tree, but again, this thing is twenty years old and never had a problem. Then I had a problem, fixed it, cut one tree, and now I have the same problem.

Just pop these little plastic pieces off and get the shroud out of the way. There's not a screw in here, don't be fooled by that, but there are four screws we have to remove to get the handle off.

Then I should be able to pull this handle off like so. We'll pull this little piece off, pull the spark plug out, and pull these two wires off. Then we should be able to pull this out of here.

This is just a rubber grommet fit, and it can be a real pain to get in and out. Then there's this little rubber grommet deal. Just push that in, and we should be able to pull this off and pull the wires through.

Don't lose this little guy. This is the vent for the gas tank. We'll leave that on there for now.

Next we'll take off the recoil starter. First let's put the clamp back on so we don't lose our gas. It would probably be a good idea to empty the gas, which I'm probably going to do anyway because I'm going to make new gas and buy some new Stihl two-cycle oil. I don't want to keep doing this all the time.

There are just four little screws that hold this on. The nice thing is all these screws are the same, so we can just throw them in our tray and not worry about sorting them.

Now we have this. The first thing I want to do is pull this little ground wire off because if I forget about it, it's going to be a problem later. This is the only screw that's really different. It's a little smaller than the others.

Now we've got to pull the flywheel. This one is a regular thread. The piece on the other side is reverse thread, so we just want to loosen this one normally. Usually a few hits with the impact takes it right off.

Then we're going to take a little punch and the flywheel comes right off. Don't lose the little keyway key. It likes to stick to the magnet, which is actually nice.

Then we need to pull this side apart. There's a little C-clip in here. Just pop that off. There's a washer on here too. Throw it in the tray.

As long as it's unlocked, this will pull right off. There's a little bearing in here we want to keep track of.

Now we're going to need a 3/4-inch socket. We're going clockwise to get this part off. If the engine turns with it, stick the spark plug back in a little bit so we get some compression. That gives enough resistance to remove it.

Pull the spark plug back out. Next, there are four bolts underneath this that need to come out.

At this point, there is nothing holding the engine together, so it should come apart. This piece slides out. This is what runs the oil pump.

Get this off the crankshaft. The bottom section is a little stuck, but with a little persuasion it pops right out.

Here's the piston itself. You can see it is badly scored. I can't even get the rings off because they're completely stuck.

This piston is pretty much garbage. The cylinder doesn't feel too bad, but they sell the whole cylinder and piston assembly, so we're just going to replace that.

This intake tube pops right off. Here are the new parts. I got this off Amazon for about $36.

It seems to be packaged pretty well, which is a good thing. We've got a new spark plug, a new cylinder and piston assembly, and an extra little piece that goes in here. I don't know why there's an extra one, but okay.

We're going to take this off. There's no sealant or O-ring in here, and it looks like there's a groove for one, so I think I'm just going to put a little Permatex in there.

We'll apply a light bead so it doesn't squeeze out everywhere.

There's a little piece right there that needs to go on the drive side because it's part of the oil pump system. That needs to be on this side or you're going to have a problem.

Then we'll put this on. It only fits one way. Stick it on with the little tab pointing down. Then we'll put this little plastic piece on and make sure we get the little hose attached.

Stick that in the hole and get everything settled. Then run the screws in from the bottom and snug them up.

Now let's put this side back together. Take our little piece and run it on. It just goes right in there.

Then we'll take this mechanism and remember that it's reverse thread. We'll start it by hand and then tighten it so it locks itself.

Take the little bearing and install it. One important thing: if you look in here, you'll see where that little lever goes. It actuates the oil pump. We need to make sure it lines up with this notch. If it doesn't, it won't go together properly.

Once that's lined up, install the washer and C-clip. It should spin freely.

Now we'll go back to the flywheel side. Install the flywheel and the retaining nut. Tighten it the same way, then reconnect the ground wire.

Next we'll install the handle assembly. Before that, put the cap back on the Permatex so it doesn't dry out.

Feed the two wires through the hole and reinstall the bushing. Then route the spark plug wire.

The next tricky part is getting the rubber boot through the hole. Carefully use needle-nose pliers and work it through without damaging it.

Then route the fuel line through its hole and reinstall the clamp. There's another little hose that connects to the orange fitting. Use needle-nose pliers and work it on.

Now we can put the handle on. Sometimes this is the biggest pain in the neck, and sometimes it goes on easily. This time it went on pretty easily.

Install the four screws and the two screws on the bottom.

Next, remove this little nylon guide so you can reinstall the plastic cover behind it. Then reinstall the guide.

Now we can move on to the carburetor. Make sure the metal tube goes into the rubber fitting. Put the gasket on and then install the carburetor.

A lot of times this area is full of sawdust and debris, so you may want to clean it out first.

Reconnect the fuel line, reconnect the wires, and hook up the linkages. One linkage is for the choke and the other is for the throttle.

Now install the intake assembly. It has a gasket and two nuts. Tighten them down.

Reconnect the wire and install the spark plug. I’ll gap it properly off-camera. Then install the air filter, which I recently cleaned. It’s not new, but it’s good enough.

Install the cover and snap it into place. The intake side is done.

Now we'll install the muffler. Insert the two mounting bolts, put the backing plate in place, and then install the muffler. Tighten the nuts and the muffler is back on.

All that's left is to install the blade. Put the blade on, install the cover, and tighten everything up. It doesn't need to be extremely tight, just enough to hold everything securely.

I'm getting some new fuel, but I'm going to try it now just to see if it works.

Okay, success.

Now we'll finish this beer and maybe a few more because it's pretty dark and late out. Tomorrow I'll get some new gas and finish cutting up this tree.