McCulloch MAC 10-10

[junglebiker]

Look what just got dragged into my shop! A pretty decent looking MAC 10-10!

Papua New Guinean guy who owns says he's had it a long time and it used to run, he just wants me to get it started. I'm guessing I'll probably have to go through the points, maybe check the carb, new spark plug? Anything else I should be aware of on these? Never worked on one before, though I have worked on a couple of similar vintage Homelites.

 

[RocketSurgeon525]

Nice find! That MAC 10-10 looks like a fun project. Along with points, carb, and spark plug, I'd check the fuel lines and tank for gunk or cracks since old fuel systems can be sneaky. Also, make sure the muffler isn't clogged and the air filter's clean. Compression test might help too, just to know what you're working with.

 

[junglebiker]

Had a chance to dig into the old 10-10 today. First I checked for spark, which was present, but seemed just a little weak to me, so I decided to check the points.. Other than a bunch of fine, oily sawdust, the inside of that thing was pretty clean and the points looked almost new. I watched Bellhopper McCulloch's video on adjusting the points, the gap was a little small, so I set them the way he said (0.019") and whaddya know? Started on the first pull. Sounds good, too. There are a couple of issues, however:

1.) the choke plate interferes with the air filter element. The way it is now, there is no way to ever open up the choke completely--I'd say about 3/4 is all you can get before the plate runs into the air filter. Works just fine without the air filter. Not sure what the problem is, I'll take a look at a parts diagram and see if there is some kind of spacer missing or something.

2.) the spark plug cap is loose and gradually vibrates off of the plug while it is running. I watched it fall off and watched the spark jumping a pretty good gap between the cap and the plug before I shut it down. This I think I can fix--I keep plug caps in inventory for other small engines, I am pretty sure I can put one of those on here.

 

[junglebiker]

Well, I got the new plug cap fitted, so that's an improvement. I also put a really small washer on the stud under the air filter element--this gives just enough clearance for the airfilter housing screw to be tightened down without actually stopping the movement of the choke butterfly. I can still feel that the butterfly is hitting the inside of the air filter, but at least now the choke can be moved all the way into the completely open position. Is this just the way they are? Or are you supposed to leave the air filter housing screw loose?

I see that some 10-10's have a screw (like the one I am working on) and some (later ones?) have a large hand operated square knob that looks a little like the gas cap. I suppose it's possibel that the air filter element itself is somewhat compressed in the area where it gets squeezed between the housing screw and the top of the carburetor, so maybe a new air filter element would fix it? I'm a little apprehensive about that little washer I put in there--I could easily see somebody dropping it down the carb. Probably I should try to convince my customer to buy a new air filter element. I see that they are still available.

 

[junglebiker]

Things are becoming more clear to me. This 10-10 must be a very early one--it has a different air filter than the commonly available one and the only one I saw that would fit the one I am working on was $85, so that's not going to happen. I also see that McCulloch must have figured out that this was an issue, as later saws actually have a steel plate that bolts over the carb and prevents the air filter from interfering with choke operation.

Anybody know if I can retrofit the later "carb bracket" to the older saw?

Here is the one I have (number 43 in the diagram, also you can see here the older style air filter element) and a pic of what I assume is a newer style off of eBay:

 

[tgile7]

Did you get it going?

 

[junglebiker]

Yup. Starts easy, runs good. I took out the little washer that I had put over the airfilter cover mounting stud and replaced it with a really short piece of fuel line about 1/8" long. This makes it possible to install the filter and the cover and screw it down tight enough to ensure a good seal all around but not pull the filter and cover down tight enough to where they prevent proper operation of the choke. I can still feel the choke butterfly rubbing against the inside of the filter when I use the choke, but at least it is now possible to open the choke all the way--it was not possible to do that before, which also means that the gap between the filter and the mouth of the carb was only about 1/16" before, so that couldn't have been helping. It's easy to see why they changed the filter and filter cover on later versions of the 10-10. I'm still somewhat astonished that this saw has lasted 50+ years here in Papua New Guinea. I mean, I suppose it could have already been an old saw when it was brought here, but I doubt it--I know that McCulloch used to be a major brand here "back in the day", before the utter domination (locally) of Stihl and Husqvarna. But in the 20+ years I've been here, I've only seen 2 complete McCullochs and a handful of peices of McCullochs and all were very old.

Now I'm just waiting for the customer to come pick it up.