MCCULLOCH The official McCulloch thread

[Al Smith]

I like to use tall nuts (this Amazon lister calls them high nuts) for bar nuts on the large frame saws.

Mark

Mc Master-Carr refers to them as "high profile flange nuts " which they carry but looking at them I could not find 3/8"- 24 size . I made a set of long nuts for a 650 gear drive and used washers under them .50 some years of use does a number on the bar stud threads .

 

[JIMG]

Hello all,
Picked up 3 old macs this week, 250 super,
7-10 and a PM80 for about US$50 all looking a bit sad. The SP80 had a broken rope so threw the 7-10 recoil on it and 5 pulls and it ran!
Further inspection, apart from paint all but gone it has no missing parts and structurally very sound.
When running seems to race slightly when idling so maybe air leak somewhere?
Always wanted to rebuild a 80cc 10-series, is there anything I should look out for? After 50 years would the crank seals need replacing?
Also find it vibrates more than my PM700 anyone have suggestion on what may be causing this?
Cheers!

I just did an 80 not too long ago. It's currently just about my favourite 28" bar saw.
This being such and old machine If it were me I would take it all the way down. I would check all rubber components, impulse line, gas line, all of the AV components (the front ones seem to wear the most), the rubber intake boot. I would clean and rebuild the carburetor and replace the intake gaskets, the crankshaft oil seals, the PTO side bearing. Check the piston and cylinder for wear, clean up the cylinder. The vibes may be due to a worn or damaged piston. Check the gas tank for leaks. Seal the tank with red kote or similar. The little phenolic disc inside the oiler sometimes wears away and you might want to check that if it oils poorly. Chainsawr had some last I checked.
I used threebond to seal the crankcase back up. No problems so far after about 8 or 10 tanks through it.
I know I'm forgetting things but that's about how I would approach it.

 

[heimannm]

dhoey - when the fuel line failed it may have sent some bits into the carburetor. Probably worthwhile to remove the carburetor and give it a thorough going over.

NZsaws - the SP80 should be much smoother than a PM700 due to the anti-vibe system. As jimg stated, give that saw a complete going over before you put much run time on it. Makes me wonder if the clutch or flywheel have a problem causing the vibrations...

Mark

 

[NZsaws]

I just did an 80 not too long ago. It's currently just about my favourite 28" bar saw.
This being such and old machine If it were me I would take it all the way down. I would check all rubber components, impulse line, gas line, all of the AV components (the front ones seem to wear the most), the rubber intake boot. I would clean and rebuild the carburetor and replace the intake gaskets, the crankshaft oil seals, the PTO side bearing. Check the piston and cylinder for wear, clean up the cylinder. The vibes may be due to a worn or damaged piston. Check the gas tank for leaks. Seal the tank with red kote or similar. The little phenolic disc inside the oiler sometimes wears away and you might want to check that if it oils poorly. Chainsawr had some last I checked.
I used threebond to seal the crankcase back up. No problems so far after about 8 or 10 tanks through it.
I know I'm forgetting things but that's about how I would approach it.

Thanks JIMG. Will start the rebuild process!
It's still got reasonable compression and all the AVs look real good so hopefully can make a good runner out of it. Older Macs are quite rear down this part of the world.

 

[NZsaws]

dhoey - when the fuel line failed it may have sent some bits into the carburetor. Probably worthwhile to remove the carburetor and give it a thorough going over.

NZsaws - the SP80 should be much smoother than a PM700 due to the anti-vibe system. As jimg stated, give that saw a complete going over before you put much run time on it. Makes me wonder if the clutch or flywheel have a problem causing the vibrations...

Mark

Hello Mark and thanks.
I feel privileged receiving advice from the kings of the McCulloch world!
As previous will start pulling apart. Looks like it's not run for 20 years so something must be a bit frozen. Hopefully nothing terminal.

 

[Maintenance Chief]

The early two man saws (5-49, 12-25, 7-55, and the 99) were all equipped with rotating counterweights to help reduce vibrations.

View attachment 437222

Counterweight cover and cylinder installed, muffler and carburetor in place with solid rubber "gaskets" to allow pressure testing.

View attachment 437223

I had to take it mostly apart again in order to apply some Dirko HT to the counterweight cover gasket and cylinder gasket to stop them from leaking.

I also pulled the primer apart to check it over, replaced an o-ring and pressed it back together.

View attachment 437224

In order to get it the gland pressed to correct depth I put a mark on this piece of tubing. I'll keep it with the two man diaphragms & carburetor parts for the next one.

View attachment 437225

Mark

Fantastic engineering for the time, it must have been a huge piece of technology for timber cutters at the time.

 

[Maintenance Chief]

A light bar on an old 81 makes a huge difference in balance and handling, .404 full comp.

 

[FergusonTO35]

One has to wonder what McCulloch would have become if they had the same sort of family leadership Stihl has. Stihl was able to continue on and thrive after Andreas died, while Mac slowly decayed into utter irrelevance after Bob's exit.

 

[Al Smith]

Regarding those bone shaker10 series it seems to me it is more prevelant on earlier 10-10 models and not so much on like the 700. As been said the larger 81 cc saws Sp81,850 etc. are the smoothest of the series .As far as the power the 81's might be old but they will still carry the mail .Not as fast as a more modern saw but that horizontal cylinder design produces some good torque .

 

[mgr1]

Titan 60, Mac 970, promac 61 piston.
Any one that has some measurements?

Overall length and compression height from top of pin?

 

[NZsaws]

Along with the SP80 came this 250.
Freed up the flywheel pawls and now runs with a shot down the carb!
Feels like it needs a carb refresh but otherwise pretty clean junk
Is it possible to identify the carb without removing it, was there a Tilly or Mac option?

 

[heimannm]

mgr1 - None of those models were prevalent here in the US. I have a 227510 piston on hand (from the Titan 560) which was the 54cc version of that saw. Piston dimensions are 1.770" diameter, 1.540" overall height, 0.830 CL of the wrist pin to the top of the piston (close as I can determine).

The PM61 piston PN is 227511, that saw was also called a Titan 620...

Mark

 

[mgr1]

mgr1 - None of those models were prevalent here in the US. I have a 227510 piston on hand (from the Titan 560) which was the 54cc version of that saw. Piston dimensions are 1.770" diameter, 1.540" overall height, 0.830 CL of the wrist pin to the top of the piston (close as I can determine).

The PM61 piston PN is 227511, that saw was also called a Titan 620...

Mark

Thanks for the info.
Piston 227511 it is. It's a 47mm piston

 

[Al Smith]

Along with the SP80 came this 250.
Is it possible to identify the carb without removing it, was there a Tilly or Mac option?

Hard to say but guessing with a black cover it could be a later model .It might be either carb but again a guess ,with a choke might be a Tilley HL.That thing could be a super ,can't tell from the picture .Now if it is a Tilly no problem but if it's a Mac flat back parts are or were not easy to find last I checked . I for one never figured out why they ever used a Mac flat back when they already had the Tilley HL.
FWIW I've got a super 250 with a flatty that has caused me to exercise my broad knowledge of profanity .If I ever get around to doing a total restore on that thing it will have Tilley HL in it's stead .

 

[Scott Kelsey]

So the SP81 and PM55 have been getting some excersize lately.
Took down a 36" willow oak that has stood beside my grandparents house as long as my grandparents could remember.
Today i started storm cleanup at our house.
Been busy with others that had it worse and just getting to ours.
SP81 just makes me smile. Its the perfect size for taking down those larger trees.
PM55 is a snappy little rascal. Makes quick work of limbs and anything up to around 18".

Guy with the SP81 is my dad. Will be 78 on 10-26 and still going strong.
No i didnt let him run it. I was greedy...View attachment 437026View attachment 437027View attachment 437028View attachment 437029

That's a beautiful 81. May I ask what size bar that is?

 

[heimannm]

MAC (Walbro) with a choke. Very nice carburetors.



Mark

 

[heimannm]

I was taking care of a few small issues on the 7-55 project. The stop switches on these are very hard to come by so I have made an effort to fix them if it is at all possible. It is a relatively simple pull to stop (make contact) affair that fits inside throttle housing on the handlebar. Jumping ahead a little, the saw is mostly assembled here...



Switch out of the saw and clamped in the vice. Carefully spread the tabs to open it up.



Well this is a problem, those two tabs are supposed to be the contacts in the switch.



I was successful in soldering the tabs back in place, well close enough to work anyway.



Here's what some of them look like. That extra tab makes the ground contact within the switch. The one above has one terminal externally grounded.



Mark

 

[heimannm]

Jeff Fox (cinci5) has been making gaskets and diaphragms for these carburetors. He includes the hollow rivets with the parts, and I drill the old rivets out and move the metal plates from the old to the new.



Jeff also made me a couple of jigs to help position the plates when putting these together.



I use some LocTite 380 around the rivets to insure they are sealed as well as around the perimeter of the plates to keep them affixed to the diaphragm. I also use a thin bead around the edges of the gasket/diaphragm to keep the assembly together.



I'll note here that there are two different diaphragms found on the two man saws and they are not interchangeable even though they look very much alike. The key is to look at the cover for the fuel channel, if it has the channel use 25945, without the channel use 18199.

Carburetor shown here is disassembled and has the fuel channel.



I had a lot of trouble getting the fuel to flow into the carburetor on this one, I tried bending the metering lever to help, took several tries to get it close to being right. This is the first time I've had to do anything other than just put the carburetor together and it was somewhat frustrating.....

Mark

 

[heimannm]

And now...my biggest act of stupidity...

I left the transmission off during my early test runs, greatly reduces the weight when carrying it back and forth outside for testing, inside for work. I installed the clutch when assembling the engine mostly so I would not lose the brass washer that goes behind the clutch.



During testing, I could never get the engine to rev up properly, always acted like it was under a great load. It also would not idle down as it should...I took a break to finish up a Husqvarna 262XP that had been setting for a couple of weeks.

Ready to give up I used compressed air to clean the saw off (I'd been running in outside on a dry patch of mostly bare ground) and noticed a cloud of black dust out of the clutch area...without the transmission in place the clutch was running against the front housing...

Test transmission in place, re-adjust the throttle cable, and we have a mostly successful runner. There are still some issues coming back to idle but it restarts easily and I think I can make a demo cut next weekend if I can touch up the chain a bit.



I will install the bow bar for the GTG to complete the ensemble.



Mark

 

[edju1958]

I finally got around to the SP125 today.All I needed to do was put the chain back on & the different nuts from the seized 1-45,right? Wrong! Every time I tried to tioghten the nuts the chain would bind.I ended up pulling the clutch to see if the needle bearing was bad or if it had a bad rim.I've never run into this before,but on my particular saw I found that I had to tighten the front nut first,then the rear nut.I also found that there are supposed to be a lock type washer behind the nuts.There were no washers on the studs previously which was why the one nut vibrated off & the other nut was loose.I got it all back together & it started right up on the 2nd pull & the chain seems to be tensioned properly.Still a lot of limbing to do on that big oak we dropped last week,so I hjave no idea as to when I'll get to use the 125 again.