Fixing a McCulloch Eager Beaver 2.0 CID Chainsaw

Back Story

My dad bought this McCulloch Eager Beaver chainsaw (Model 60012312, 2.0CID) in 1987, and used it up through the mid-90s, when he replaced it with a bigger Craftsman saw. The little McCulloch sat in the garage for a while, then sort of disappeared. Years later, I found it in the same place as my old boombox: buried in a brush pile in the back yard. If you've read some of my other articles, you'll know that I never throw anything away if I can fix it. Considering that not all of the parts were there, and that it had been sitting out in the weather, half buried in dirt, leaves and bugs for over 10 years, it would be a challenge, but I like to think that there's nothing I can't fix.

I found an old junk saw of the same model on eBay for $10, it didn't work either, but it had all of the parts this one was missing and the price was right.

Disassembly and Cleaning

Getting it apart was actually pretty straight forward. There was a lot of dirt and bugs inside, since it had been sitting outside for years and years, but none of the screws were overly corroded. To disassemble it you cut the cord on the pull starter, remove the starter, remove the handle bar, then the hand guard. There are three or four long hex screws holding the housing to the crankcase, once you remove those everything should just slide out.

The flywheel is friction fit to the crankshaft. To remove it loosen the nut (the threads are reverse) and use a wood block and hammer to pound on the crankshaft. The shaft should pop loose after a few knocks. Be careful not to lose the little alignment key.

Be careful when removing the clutch. Like most saws, it has a centrifugal clutch, which uses a powerful spring to hold the two halves of the clutch together. If the spring is damaged or the clutch is cracked, discard it safely and replace it. New ones are only a few bucks.

To clean everything I just soaked it in paint thinner overnight and washed everything down with Simple Green the next day. The inside of the cylinder still looked a little rough, so I wrapped some paper towels to a drill bit and polished the inside of the cylinder with some polishing compound and water.

Reassembling the Piston and Connecting Rod

This part is not fun. This is where you have to cram all of those little roller bearings back into the connecting rod and somehow get the wrist pin back in without them going anywhere. There is a secret trick, though: grease. Pack the inside of the connecting rod bearing with grease, then insert the roller bearings one at a time. It's tedious, but the grease holds the bearings in no matter which way you turn the rod, so getting them all in isn't that hard. Be sure to count the bearings as you're putting them back in, leaving one out could be really dangerous. There should be 21 bearings, there shouldn't be any space between them, and you should be able to slide the wrist pin in with little to no resistance. Go ahead and attach the connecting rod back to the piston. Slide in the wrist pin in one fluid motion, being careful not to knock any bearings out of the connecting rod. It should go pretty easy if you've greased everything well. Make sure the circlips are seated in their grooves.

The crankshaft end of the connecting rod is a little easier, since it's open ended. Packing the bearing with grease still helps, though. Pack ten bearings into the connecting rod, and ten more into the rod cap, then gently press them together around the crankshaft journal and tighten the bolts. Torque them down pretty tight.

Measure the new rings against the old ones. Start by placing an old ring in the cylinder and squaring it with the piston, then use a feeler gauge to measure the gap. Do the same with the new rings. If the new rings have a smaller gap, use a sheet of sandpaper to grind them down to the same size as the old rings. Seat the new rings in the ring grooves. Actual ring pliers help with this step, but if you're cheap you can do it by hand, just be careful not to stretch the new rings too much, they're pretty fragile. It doesn't matter where the gap in the rings are, they'll rotate around the piston a little on their own at first.

Fixing the Sprocket

I had two sprockets: the one from my saw was in great shape, but had a rusted stuck bearing; the one from the junk saw had a worn sprocket with a good bearing. Fortunately, these are just press-in roller bearings. I removed the good bearing from the bad sprocket by putting it in a vice with a 9 mm socket on one side of the bearing and an 18 mm socket on the other side, then tightening the vice. It works as well as a bearing press, but has the advantage of not costing anything. Then all I had to do was pop the good bearing into the good sprocket.

Cleaning and Rebuilding the Carburetor

This saw uses a Zama model M1/M7 carburetor. I disassembled the entire carburetor for this step, here's how to do it. Remove the four screws on the bottom and remove the fuel pump casting, gasket, pump diaphragm, plastic spacer, gasket, metering diaphragm, and metering disc. Take out the screw holding in the metering lever, then remove the lever and needle valve, being careful not to lose the tiny spring that holds the metering lever up. Underneath the welch plug is a small fuel passage leading from the hole where the low speed needle goes to the three tiny low speed mixture jets inside the barrel of the carburetor. Since the rebuild kits I've seen don't come with one, I'd recommend leaving it alone unless you know the low speed mixture jets are clogged.

The brass thing you see in the middle is the main jet nozzle, it's connected to the hole where the high speed mixture needle goes. It can be pressed out using a vice and a metal rod smaller then the nozzle's OD, but I don't recommend removing it unless the check valve is damaged or there's solid dirt inside the small fuel passages inside it that can't be blown out with carburetor cleaner. Unscrew the high and low speed mixture screws, along with the idle speed setscrew.

If you're going to remove the choke and throttle valves, start by removing the brass screws in the butterfly valves. Don't put a lot of downward pressure on the screws, doing so will bend the shafts and cause them to bind when they're reinstalled. The shaft of the choke valve can be pulled out, but there is a tiny spring and a ball bearing (this is what holds the choke open) buried in the casting which will pop out of the tiny hole to the right of the air intake and disappear if you're not paying attention. The throttle valve's shaft is held in place by an E ring, and will slide out easily once it's removed.

Separate all of the "soft" (plastic and rubber) parts: the diaphragms, gaskets, needle valve, plastic disc, and spacer, from the "hard" (metal) parts. After cleaning with a brush and soapy water to remove any large dirt, the hard parts should be soaked overnight in the main ingredient in carburetor cleaner: acetone. It's great for removing grease and the varnish left by stale fuel, but it dissolves some plastics; don't get any on any of the soft parts. Drain off the acetone, then add the soft parts and soak everything in a gentler solvent like mineral spirits or kerosene. You can use a wire brush on the aluminum casting. Use a pipecleaner soaked in acetone or paint thinner to clean out all of the holes and fuel passages. Then use compressed air to dry the parts, and blow any remaining particles out of the four million tiny intricate holes in the castings.

It's probably a good idea to replace the diaphragm and all of the gaskets, even if they're not excessively worn. Gasoline nowdays pretty much always contains some percentage of alcohol, and the old soft parts aren't designed for that. The rebuild kit for this carburetor is Zama part number RB-19. It's been discontinued, but NOS and repro kits can still be found on the net; Sears stocks a lot of old parts, if you can't find it there try Amazon and eBay. It comes with a little mesh screen, which is installed on the fuel pump near the fuel inlet.

The reassembly order goes like this: metering lever and needle valve, plastic disc, metering diaphragm, gasket, plastic spacer, gasket, pump diaphragm, fuel pump. After reinstalling the metering lever, bend it up or down so that it sits flush with the gasket surface of the casting. Either the carburetor cleaner, or modern ethanol-gasoline blends will have dissolved the sealant on the welch plug; use a solvent resistant sealant like Permatex to replace it. Be careful to align all of the gaskets to the holes in the body of the carburetor, one hole supplies pressure pulses from the engine to the fuel pump, and another supplies pressurized fuel from the pump to the carburetor. A blockage or leak in either one will prevent the carburetor from working.

If you took the choke and throttle valves out, reinstall them now. Twist the throttle valve one full turn to tension the spring. Poke the tiny spring, followed by the tiny ball bearing into the tiny hole to the right of the air intake and slide in the shaft of the choke valve. Install both butterfly valves. The brass valve is for the throttle and the steel valve goes on the choke. Tighten both of these screws very well and use threadlocker, the consequences of one of them coming loose is pretty grim. The holes in both valves should be covered completely by the shafts.

Reinstall the idle speed screw, then the high and low speed adjustment screws. The long needle is the low speed needle - don't mix them up. Tighten both needles all of the way, then back them out one full turn.

Manufacturer's Disassembly and Servicing Instructions
How Tiny Carburetors Work
I feel kind of special since somebody from the Zama company actually took time to respond to my request for a parts list and assembly diagram for a 25 year old carburetor. I really can't tell you how much I love it when a company stands behind its products. Thank you Zama.
Parts List
Assembly Diagram

Photo Gallery

The carburetor assembled.	All of the carburetor components.	Assembling the carburetor.
Replacing the clutch/sprocket bearings.	Removing the clutch.	Removing the crankshaft and piston.
Replacing the crankshaft bearings.	The inital disassembly, after soaking thoroughly in penetrating oil.	The finished product.
The socket for the oiler. I drilled this out and fitted it with an automatic oiler.	Reassembling the piston.	Inserting the retainer for the wrist pin.

Specs

• Displacement: 2.0 CI/33 CC
• Power: 1.8 HP/1.35 kW
• Fuel Mix: 20:1
• Spark Plug: Champion DJ8J or equivalent
  
• Air Filter: 216905 or 91460 or 214224

Instruction Manual

You wouldn't believe the time I had trying to find a manual for this thing. The McCulloch company that made this saw doesn't technically exist anymore, having been bought out by like 5 other companies since this thing was made, and is currently owned by Husqvarna, along with Poulan, Jonsered, and Weed Eater. They weren't any help. If you do a web search for this manual, most of the stuff that comes up is weird virus and spyware sites that I'm pretty sure are owned by the Russian mob. I finally did find one, even though I did have to pay for it. So here it is, free for the taking.

• McCulloch Eager Beaver and MAC 100 Series Operator's Manual