McCulloch Chain Saws

[rwoods]

I have never had a problem with any of my 82cc MACs leaking bar oil - until I gave one to my brother. He eventually gave it back because it poured oil. Sure enough after running, it would leak copious amounts of oil. I couldn’t figure out the problem. As MAC fate would have it, the fellow I bought it from years earlier contacted me to see if I still had it and would I sell it back to him. Being blessed with an abundance of these saws and having experienced seller’s regret myself many times, I readily agreed. I warned him of the unresolved oil leak. He fooled with it and eventually tracked it down to the adjustment screw being backed out almost completely. Why this would cause a massive not-running leak, I don’t know. Anyway he said tightening the screw fixed the leak and it oils fine.

Ron

 

[fossil]

To follow up on the chain issue...

For some reason the chain had tightened itself up after those few minutes of running. I loosened the bar nuts and then it could be pulled around freely again. But while I was trying to set the tension after that it would do the same thing repeatedly. If I got it just a bit too tight it would lock up. In order to get it to stay free-moving I had to have it adjusted a little looser than I would normally run a chain. I'm sure it has to do with the fact that the bar is ancient and the chain has seen its better days too. Now that the saw is running I will get a new bar and chain eventually.

I did use it for a while. Used it for what is probably the least appropriate thing you could do with a PM800... cut the sucker branches off all the maples and other trees on our property. My arms are still sore! But it ran and cut well! There is just a slight bog after idling for a short while when I go to give it gas again. A quick blip of the throttle and it clears up. I'm sure a little carb adjusting will make things better.

And why oh why do these Macs leak oil SO BADLY!! This restored PM800 and the running PM800 I just bought leak it like a sieve. I do have a new gasket I'm going to try on one of them but damn it sucks!!

Rob

Do you have a rim set up or a spur on it? Worn spurs will cause the chain to follow a different path sometimes and when they jump out of the worn groove the chain tightens a lot. If that's not the issue do check the length of the chain against a newer one. Sometimes they do stretch a little too far and bind up. Just like it's the wrong pitch.

The oil tanks on mine do leak some. If you don't plan to go back into the tank to adjust the oiler you can put a little Motoseal or some sealer on both sides of the gasket.
I do think there's a sweet spot when tightening up the cover. If you go too far they seem to leak more.

 

[heimannm]

If the cover has been overtightened in the past it is possible it has been distorted or cracked. The later models like the PM had some additional stiffening ribs cast in but that is not always enough.

The OEM gaskets are pretty thin and that doesn't help. EBay seller gotfishon has some nice reproductions from slightly thicker material that work nicely.

Mark

 

[Darrin Cromwell]

Ah. Maybe that's what it was. Well, it's over now. I pulled it out and put in in a few times to see if I could loosen things up. I looked at the ring end gap in the exhaust port and it looked fine. But it was still pretty sticky when going above the exhaust port. Finally, when I was pulling it back out it came fast at the end and the top ring must have caught on something as it exited the cylinder. Cracked a 3/8" chunk out of it. Ring is no more.

The good news is that with only one right it slips in and rotates just fine. Regardless of whether that one ring is in the top or bottom groove. So something was definitely up with the one ring. Anyway, I'll need to find a new ring now and get back to it later.

Walter - How did you reduce the ring width? I assume this means slightly increasing the inside diameter of the ring, right? Did you just use a grinding wheel or sanding disc on a dremel and free-hand it around the inside of the ring?

Really appreciate the guidance folks!

Thanks,
Rob

McCulloch pistons have a cold rolled pin at the slit of the ring to keep them positioned properly

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[BigBlue]

McCulloch pistons have a cold rolled pin at the slit of the ring to keep them positioned properly

Thanks. I had learned that earlier. That didn't have anything to do with my issue. My issue was with a ring that apparently was too 'deep' in the radial direction, which caused it to stick in the cylinder because it couldn't get into the ring groove far enough. A replacement fixed that. Interestingly, I had to buy a set of 2 rings and one of the replacements was also too deep. The saw is back together and running now, as reported back a few posts.

Rob

 

[heimannm]

I found the chainsawr pistons and rings don't fit properly, the groove is not deep enough and the rings stick out too far and bind in the bore. I solved this by making a simple jig to hold the rings in my lathe and took the Dremel with a small stone to reduce the width of the ring so it would fit. Walter Glover ran into the same issue and came up with the solution first.

And not all McCulloch saw and kart engines used a locating pin for the rings. Certainly later mode 10 Series did, but many others did not.

Mark

 

[fossil]

Question for you large MAC saw guys.

I finally collected all the parts I think I need to button up the CP125. I am putting the clutch and sprocket on and have a question about the thrust spring washer between the drum and the clutch shoes.
The ID of the washer is much larger than the crankshaft at the clutch. It certainly doesn't look right to me. This was the washer that was in the saw as purchased.

Am I missing something or is that the way it's supposed to be.

That aside, I'm not sure why a flat washer wouldn't work.

 

[leeha]

That's the way they are Tim. Put it in and go.

 

[fossil]

That's the way they are Tim. Put it in and go.

Thanks Lee

 

[heimannm]

Many, if not all of the saws with those spring washers have the felt washer adjacent to the PTO side seal. I think the point of the spring washer was to keep the drum fairly tight to the felt to keep stuff from getting in there.

Mark

 

[fechtichmac]

Thought the same...
and the felt disk should be oiled frequently.
Think , in some OM they wrote that.

Many, if not all of the saws with those spring washers have the felt washer adjacent to the PTO side seal. I think the point of the spring washer was to keep the drum fairly tight to the felt to keep stuff from getting in there.

Mark

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[fossil]

Thought the same...
and the felt disk should be oiled frequently.
Think , in some OM they wrote that.

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From a manual. I only have a piece of that manual but it looks like a MAC publication.

 

[Neat_Hedgehog]

Mac 2-10


A little rough around the edges, as you can see from the dowel handle and flaking paint. But it runs nice. ...when it runs. I didn't want to take a picture without knowing it ran (it ran last year), so I cranked it over yesterday... nothing. Didn't seem to be sparking under compression, no pop even with ether (although the little fire cloud from when I tested the plug too close to the hole said it worked ok without compression, haha), so since it was too hot to do anything else today, I freshened up the points, reset gaps, shot all the contacts with electronic cleaner. Now it's running good.



That's still the original bullfrog in there. I didn't want to convert it since they're such a goofy design it makes me nostalgic. I have over bored the inlet for the primer to fit a Homelite duckbill, though.

 

[fossil]

Sort of got the CP125 running today. To say it oils would be a gross understatement.

The saw feels like the timing is way advanced. I set the points at .021 and the FW key is in there but it kicks back hard when it dies at a low idle.

I'm having trouble tuning it. It sort of wants to idle but not well I tried the recommended initial setting at 3/4 idle and 1-1/8 high and played with it from there. Rev's up well.

I really feel I have carb issues. I think I'll take a run at that first.

That saw really has a nice bark to it at idle.

 

[brandonstc6]

I have a Mcculloch 795. Someone has swapped it over to a Tillotson HL carburetor. Is this better than the Mac carburetor? Also, the fuel line is broken off. Will a replacement fuel line work with the Tillotson carburetor? Also where can I get a fuel line for one?


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[Walter Glover]

Sort of got the CP125 running today. To say it oils would be a gross understatement.

The saw feels like the timing is way advanced. I set the points at .021 and the FW key is in there but it kicks back hard when it dies at a low idle.

I'm having trouble tuning it. It sort of wants to idle but not well I tried the recommended initial setting at 3/4 idle and 1-1/8 high and played with it from there. Rev's up well.

I really feel I have carb issues. I think I'll take a run at that first.

That saw really has a nice bark to it at idle.

Tim do youhave a DVM to check points opening? Need to confirm timing advance first.

 

[sawfun]

I set my points from .015 to .017 on those large Mac's.

 

[Drptrch]

I have a Mcculloch 795. Someone has swapped it over to a Tillotson HL carburetor. Is this better than the Mac carburetor? Also, the fuel line is broken off. Will a replacement fuel line work with the Tillotson carburetor? Also where can I get a fuel line for one?


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I swapped mine over to a HL 63A , choke now, no primer like the flatback and it starts and runs better. The primer rod and button now operate the choke.

Erik

 

[fossil]

Tim do youhave a DVM to check points opening? Need to confirm timing advance first.

I do. No degree wheel though.

I set my points from .015 to .017 on those large Mac's.

I'm using the setting that's listed in the IPL. I've also seen .020 in a manual.

 

[emf123]

I do. No degree wheel though.

I'm using the setting that's listed in the IPL. I've also seen .020 in a manual.

That was the initial setting from the factory, however they changed it to .016 on the karts and big saws. It was posted in a service bulletin, I was just looking at it, so I'm absolutely positive of the info.

Eric