I periodically stop by pawn shops to browse. Being a DIY junkie, I can never have enough tools in the shop. Pawn shops can have some good quality tools at really good prices, you just need to catch them while they are there. I recently stopped by one of the shops and found an old Craftsman 20″ chainsaw, Model 358-351202
They let me take it outside to test it. It started and ran after a couple of pulls. The chain was in good condition. So I took it home for $25. At home I gave it a bit more testing and found that it wasn’t oiling the bar when I ran it. So I put it up and earmarked it for a future chainsaw restoration project.
Unfortunately, while testing it, I had put a 40:1 mix with ethanol. When I took it out a few months later a second problem had evolved. It would only run for 30 seconds or so and stall out. I figured the carburetor had gummed up because of the ethanol.
The carb should have been an easy fix. In the past, I’ve just gone to ebay and bought a carb for other gas tools. They usually ran about $15.00. As it turned out, this carb (Walbro HDA-49-1) was no longer manufactured and scarce. The ones that were were available ran around $100.00. So I fell back to rebuilding the carb.
Preparing for the Chainsaw Restoration
I ordered a carb rebuild and a fuel line kit for it. I also downloaded the Walbro manual as well as the craftsman manual for the chainsaw. I’ve rebuilt a few Walbro carbs in the past, thankfully their manuals are readily available for download. Once I had everything together I started the rebuild.
While disassembling the chainsaw, I noticed that there were a few bolts missing. I made a list of these so I could later go down to the ACE hardware store to get replacements. Ace is a great place for nuts and bolts, if you cant find what you need there, it probably doesn’t exist. So here are the basic steps I took to get this chainsaw up and running
Chainsaw Bar Oiler
Before going in after the carb, I wanted to make sure the oiler worked. I took off the chain bar cover and removed the bar and chain. The problem was I had suspected. There was a huge buildup of old sawdust and oil blocking up the whole works. I cleaned that out by
- spraying it liberally with engine cleaner (the non foaming kind).
- Use compressed air to blow out all of the gunk that was built up in that area.
- Reassemble the bar, chain and cover.
- Run it for a few 30 second bursts.
I saw that the chain was leaving a nice streak of oil on the ground. Satisfied that the oiler was good I went on to the next step.
Chainsaw Restoration – The Carburetor
Here are the steps I used to rebuild the carburetor.
- Removed the cover and air filter
- I noticed that the air filer was fairly clogged up so soak it in a mixture of water, dawn dish washing detergent and ammonia
- Removed the choke and choke linkage
- Disconnected the fuel line
- Removed the two nuts holding the carb on to the manifold
- Pulled carb out while simultaneously unhooking the throttle linkage
At this point I noticed that there was another fuel nipple facing the inside of the chainsaw. This was for an impulse line, unfortunately the old line had disintegrated. A quick look yielded no clue as to where it was supposed to go. I eventually figured this out and you can see in the section for replacing the fuel line how I found where it went. I learned a long time ago that pictures are worth a thousand words when re-assembling anything. So I took a series of pictures as I disassembled the carburetor (See below). I laid the parts out in the order they were disassembled.
Disassembling the Carburetor
- Disassembled fuel and impulse side of carb
- Disassembled metering and pump side of carburetor
- Removed fast and slow idle screws
- before removing these I screwed them all the way in until they stopped, carefully counting how many turns it took. That way when re-assembling the carb, I could set them back close to their original positions. I would probably change that when tuning the carb but I think it is a good reference point to start at. You can see the notations I made on this in the middle picture above.
- Gave the carb body and covers a 4 hour dunk in carb cleaner
- Rinsed the carb body out with water and blew it out with compressed air
- Using the pictures (and at times the Walbro manual)
- reassemble the fuel impulse side of the carb with new components
- reassembled the pump side of the carb
- I used the new needle valve included in the rebuild kit but kept the old metering lever. My thoughts are that it was in excellent condition and would need no adjustment. The walbro manual specifies that the back of the metering lever should be flush with the body of the carburetor without lifting the metering needle. This proved to be true (see picture).
Installing the Carburetor
- Installed the carb on the chainsaw. Before installing it I made sure to inspect the gasket. This saw had a two part gasket. The first part had a metallic lip that fit into the manifold. It also had a rubber backing. The second part was a metallic gasket that fit against the rubber and sits between the carburetor and the first part of the gasket. I cleaned the metallic gasket and bolted the carb in. The throttle linkage was a bit challenging but I was able to get it in with a bit of wiggling.
Fuel and Impulse Line Replacement
As part of getting this saw back in shape I thought it would be a good idea to replace the fuel line. As you read earlier, there was also a secondary line on this car. That line is the impulse line. An impulse line on a carb uses pressure from the cylinder to drive the fuel pump in the carb. The nipple on the cylinder is typically below the level of the piston. It proved to be difficult to find on this particular saw.
Finding the Impulse Nipple
I ended up taking off the starter. Once I had the starter off it took no time at all to find the impulse hose nipple. it was on the side of the chainsaw where the starter was, and I could see remnants of the old hose as well a hose clamp attached to it. You can vaguely see it in the picture below on the left. The challenge was how in the world was it originally routed? I followed the wiring for the on off switch on the handle and saw that the wires went through a small hole in the carb compartment. I poked the hose through there and miraculously, it popped out right where the impulse nipple was.
After a few gymnastics with a long needle nose pliers I was able to get the hose on to the nipple. Feeling adventurous, I also attempted to get the hose clamp on it as well. Luck appeared to be with me on this as I was able, after a few attempts to get the clamp on as well. You can see this in the picture below on the right.
Putting The Chainsaw Back Together
I put the saw back together, in the reverse order that I had taken it apart. Put some fresh fuel in it and took it outside for a test run. It started right up and ran well, both at idele and at full speed. There was one small hitch though. At full speed the automatic oiler spewed oil like a Texas gusher. I did a bit more research and found that this model had an adjustment screw at the bottom of the saw (see picture). Turning the screw clockwise decreases oil flow and counter-clockwise increases it. Of course it was backed out almost to its stop position. I adjusted it back down and ran the saw. The oil flow was normal now.