Restoring a Chainsaw – Carb Adjustment and Sharpening – Part 2

Craftsman 20" Chainsaw Restoration

Now that the carburetor has been put in, it’s time to finish the chainsaw and put it to a test. I did find one problem, the chainsaw was leaking oil. When I looked into the saw, I found that at some point, the chain was off the guide and chipped the area where the oil gets fed to the chain bar.

After I address that,  I’ll be doing a carburetor adjustment for the fast and idle mix. Subsequently, I’ll be sharpening the chain, and will then tension the chain and take it out for a few quick cuts. I’ll show step by step, how to sharpen a chainsaw and what chainsaw sharpener to use.

Chainsaw Oil Feed

Before I sharpen the chainsaw, fixing the oil well that got chipped was my first priority. I’ll tackle that first before moving on to the carb adjustment. I’m not usually a big fan of JB Weld. Since this saw will only see occasional use, I would try using that for a repair. I thoroughly cleaned the area where the JB Weld would be applied. I then mixed up a small batch and built it up around the repair area. It was important to let the “weld” cure, so I let the repair sit for 24 hours.

Applying JB Weld to Oil Well
Applying JB Weld to Oil Well
JB Weld Filler Before Filing
JB Weld Filler before filing
Filing the JB Weld Fill Flush with the Oil Well
Filing the JB Weld Fill Flush with the Oil Well

After that, I carefully filed down the weld so that it was flush with the rest of the oil well. Carefully filing around the contour was my next step. I did not want to leave any bulges or projections that the chain might catch on to.

On to the first test. I wanted to see if the repair to the oil well would work. I put on the bar and chain and attached the cover. Taking it outside I ran the saw at high speeds. I could see a nice strip of oil being sprayed on the ground. It seems to be holding fine so now on to the carb adjustment.

Carburetor Adjustment

Making a carb adjustment on a chainsaw may seem intimidating but is relatively easy. Small engines have two idle adjustments, a low speed and a high speed idle adjustment. The picture is hard to see but in the slot, there is a low speed idle adjustment on the left,and a fast idle adjustment on the right. In any event, they will be clearly marked on all carbs. The large screw on the top is the where you adjust the idle speed. To adjust the fuel mixtures, first turn both the fast and idle screws all the way in and then back them out one turn.

Next I want to make to make sure the bar is clean with no obstructions. Do this by running the edge of a paint scraper along the ridge in the bar. Before putting the bar and chain on I also applied some 30 weight oil to the sprocket on the tip of the bar.

Cleaning the Chainsaw Bar
Cleaning the Chainsaw Bar

Idle Mix Carburetor Adjustment

Clean the air filter before proceeding. Start the saw and let it warm up. Adjust the idle speed slower until the chain just stops moving. Start with the idle mixture. Turn that screw clockwise, listen for the engine to start picking up speed. At that point, turn the idle mixture screw counter-clockwise until it start to speed up again, if you keep going it will start to sputter and slow down, stop there. Turn the screw slightly clockwise again so that the engine runs smoothly. Ideally, this point should be between the two points (Clockwise and counter-clockwise) but closer to the rich side.

Chainsaw Idle Speed fuel mix Adjustment
Chainsaw Idle Speed Adjustment
Chainsaw Idle and Fast Mixture Screws
Idle and Fast Mixture Screws

Fast Idle Carburetor Adjustment

After adjusting the idle mix, I re-adjusted the idle speed and went on to the fast idle adjustment. Running the saw at wide open throttle, turn the screw clockwise, the saw will start to speed up. Do this in short burst as teh engine is running very lean at this point. Once you find the point where the engine is running very fast, slowly back the screw out counter-clockwise. The engine should decrease speed and then start to accelerate again.

Continue backing the screw out in short increments. At some point it will start to have a muffled sound and run a little rough. Stop there and turn the screw clockwise a small amount until it runs smooth again. It should be running slightly rich at this point which is where you want it. Now that we’ve finished with the carb adjustment, it’s time to move on to sharpening that chainsaw.

How to Sharpen a Chainsaw

Before doing a test, I wanted to sharpen the chainsaw. What seems like a tedious job is actually quite easy.  I’ll cover all the details on how to sharpen a chainsaw here. The two key areas you want to focus on are the depth gauge fins and the actual cutting teeth. I’ll start with the depth gauge fins. The depth gauge fins are there to control the depth of cut. If they are too tall, the cutting teeth will not be able to reach the wood you are trying to cut. To short and the cutting teeth will dig in to deep, increasing the chance of the saw kicking back. You should use a depth gauge guide and file, similar to this one. Depth gauge and File.

Depth Gauge Fins

First, clean off a spot on one of the cutting teeth with acetone or alcohol. I do this to mark where I am at on the chain. Use a sharpy to mark the spot you just cleaned off.

Marking chainsaw chain With Sharpie
Marking chain With Sharpie
Chainsaw Depth Gauge Filing
Chainsaw Depth Gauge Filing

Place the guide on the chain so that the guide is sitting on the cutting teeth, exposing the depth gauge fin in the slot in the middle. Using a fine tooth file, gently file the fin down so it is flush with the dip in the guide. Move on to the next one and continue down the length of the chain. When you’ve reached the spot you have previously marked you will be complete with the Depth gauge Fins.

Chainsaw Sharpening the Cutting Teeth

The Right Chainsaw Sharpener Tools

Start at the location you previously marked. The key chainsaw sharpener tool is a fine toothed rat-tail file with a depth guide. You want to make sure you have the correct file size. The cutting teeth typically come in three sizes; 5/32, 3/16 and 7/32. You should be able to find the correct angle on the chain itself. The chain guide that goes into the slot on the bar is usually marked with the correct size. Saw chains are easily sharpened if you use the chainsaw sharpening guide seen in this picture. The guide will keep the file to the correct depth and is inscribed with the correct angles to use when sharpening the teeth, typically most saws have the teeth set at a 30 or 35 degree angle.

Sharpening the Cutting Teeth

Looking at the picture, you can see that the file and guide are placed on the chain. The file is resting inside the tooth. The guides is positioned so that the guide angle at the top is aligned with the cutting edge of the teeth along side it. Gently slide the file forward applying light pressure down and against the tooth you are sharpening. When filing the cutting teeth, always file in a forward motion. Several light passes should do the trick. I have noticed that after a few passes, the resistance lessens. To me that means that I am done with that tooth and I move on to the next. There are other chainsaw sharpener tools, but you will find that the rat tail file with a guide is one of the most common sharpeners available.

Chainsaw Sharpening Angle and Depth Guide
Chainsaw Sharpening Angle and Depth Guide
Running File Forward to Sharpen chainsaw tooth
Running File Forward to Sharpen tooth

Continue along the chain. I prefer to just work on the teeth that are all at the same angle until I have gone completely around the chain. Turn the saw around and begin on the teeth that are at the opposite angle of the ones I just completed. I recommend wearing heavy work gloves when sharpening a saw. Personally, I prefer to do this bare handed (carefully of course). There’s a certain feel to the file when the tooth you are sharpening is done which is easier to feel bare handed.

Testing the Chainsaw

Now that the oil feed is repaired and the saw has had a carb adjustment and been sharpened it’s time to give it a test. I fired it up and let it warm up. I tackled some of the dead fall that we had from the last few hurricanes that brushed by us. The saw ran like a champ and cut through several tree limbs effortlessly.

Here’s a short video of me testing the chainsaw and some dead wood that was blown down during the last storm (2018 Hurricane Michael). This was hardwood, not rotten!

On a final note, I found a sharpening add on tool by Dremel. Dremel Sharpening Attachment. I have ordered one and am going to try it to see how well it works. I’ll write a review on it and pass on my experience to you.

Part 1 of the Craftsman Chainsaw Rebuild – Part 1