McCulloch Chain Saws

[McCullochKid]

So while thinking about the G-70 with a fresh mind today, an idea came to me.
Are the fuel tanks more or less the same on these 10 series saws? I have an extra 10-10A that is a bit beat up and missing a couple things, but the fuel tank is fine on it. Could I just do a switcheroo and swap that tank onto the G-70? That way I wouldn't have to buy a new tank, and if the SDC that is on the 10-10A is appropriate I could use that too.
I even have an extra carb kit for that ready to go, so I could possibly have the G-70 running and ready to go into some wood very soon if I can just swap stuff around.

 

[vinnywv]

You should be able to just fine. Most all the ten series parts interchange.

 

[Maintenance supervisor]

The air filter cover is mostly the only difference, but some had adjustable carbs through the tank also.
There's not a big difference between the carburetors either , some are very good runners though sdc44a for me and the old reliable sdc37. I'm also into the sdc 65 where a fixed jet was. So i order of how I listed my favorites here , long needle ( through the tank adjustments) ,short (strait) needles, and fully adjustable (angled) needles.
I believe that the venturi diameter only varies by 2mm from smallest to largest.

 

[heimannm]

The smaller SDC numbers (16 and below) have a .625" venturi, the larger numbers (18 and above) have a .750" venturi. The difference doesn't seem to noticeable on smaller saws, but does make a difference on the SP125.

I have been working off and on on this junk yard dog SP125 project lately. I had some parts in a box ready to sell but the buyer never came through and I wanted a test bed for a 3D printed intake boots I have been working on (TPU or Thermal Poly Urethane material). With some help from Vinny and Leha I think I have everything needed to put it together and give it a go. It is a conglomeration of mostly worn out, broken down bits but it will serve the purpose intended. The mounting holes for the muffler were evidently wrecked at some point and the previous owner drilled them out and tapped them 5/16" so I will stay with the CP125 style muffler for now. I was able to find a NOS muffler cover in the attic along with a decent spark arrestor screen. The only lower brace I have that isn't broken has badly corroded so I sand blasted it clean and an working on getting it patched up with some JB Weld.

The AF cover had been modified for improve flow.



If I can't locate a keyed clutch I will cut the ears off this one from a RH start saw.



I will need to rebuild a different fuel cap, this one is used when I am cleaning out a fuel tank with the BB's by rotating it slowly in the lathe.



I already located an oil cap, manual oiler works but I haven't been able to confirm the automatic oiler works yet.



The clutch cover had a hole in the back that I have already patched with JB Weld, and this crack. I will paint it and use it as is until I find a better one.



I have a few more pieces in this box plus a few more boxes that I have already taken over to the new building.



This shroud is in much better condition than the one currently on the saw so I will change it out.



This is the lower brace that was badly corroded, currently undergoing JB Rehab.



The saw starts well, idles nicely, revs responsively, and generally sounds good. I thought I'd measured the compression at 90 PSI but I can assure you it is much higher than that now that I've run it a bit. I will add one of my steel full wrap handle bars and use 3D printed clamps when the time come.

Mark

 

[emf123]

Hey Mark, I see your junk yard dog is coming along nicely, just like mine!
My clutch cover was cracked in the same place, actually worse than yours. Lots of JB weld and bondo in mine, there's lots of casting voids to stuff it into to reinforce it. It's actually going to get painted soon. I got the fuel tank, air filter cover, oil tank and brace painted black. The rest of the pieces will be yellow.

 

[McCullochKid]

Got started on the tank swap today. Getting the tank off of the G-70 was a straightforward yet frustrating process. Once I started digging into it I realized just how completely filthy the saw is, especially the area between the main body of the saw and the gear case... I have no clue where to begin on getting that spot clean lol.
To make matters worse there's this weird thick grey grease everywhere. It appears to have been applied mainly to the pull rope mechanism, but it's also present on a lot of the screws like it's some sort of threadlocker.
Despite my best efforts to avoid doing so, some gunk broke off and fell into the intake where its resting on the side of the piston. I got most of out out but some small specs of it fell deeper in where it's hard to reach. Is there a good way to flush that out somehow, or do I need to split it in half now to clean it properly? I was hoping to avoid that for now.

Beyond that, I did a test fit of the upper half of the G-70's fuel tank on the 10-10A lower half that I was hoping to use. It appears to fit great, and thankfully the top plate thingy from the Tillotson carb fits right onto the SDC, so the air filter cover screws on tight like it should. I think the all-yellow look is pretty cool too.





The only issue I could find is that there doesn't appear to be any thread on the two holes seen at the bottom here. I don't know if they're covered up by paint or if they just weren't used on this 10-10. Thoughts?
By the way, I'm not sure if this is even an original McCulloch fuel cap or not, but do you put a new rubber check valve in this like the normal plain square McCulloch fuel cap? I'm not exactly sure what's going on with the metal tab here.

 

[mogulmasher]

That metal on cap is for a chain so you don't lose cap when fueling. My 10-10s has it all intact on gas cap and also on oil fill cap. First of many Macs I've had that actually has had this feature.

 

[Brian Thacker]

The smaller SDC numbers (16 and below) have a .625" venturi, the larger numbers (18 and above) have a .750" venturi. The difference doesn't seem to noticeable on smaller saws, but does make a difference on the SP125.

I have been working off and on on this junk yard dog SP125 project lately. I had some parts in a box ready to sell but the buyer never came through and I wanted a test bed for a 3D printed intake boots I have been working on (TPU or Thermal Poly Urethane material). With some help from Vinny and Leha I think I have everything needed to put it together and give it a go. It is a conglomeration of mostly worn out, broken down bits but it will serve the purpose intended. The mounting holes for the muffler were evidently wrecked at some point and the previous owner drilled them out and tapped them 5/16" so I will stay with the CP125 style muffler for now. I was able to find a NOS muffler cover in the attic along with a decent spark arrestor screen. The only lower brace I have that isn't broken has badly corroded so I sand blasted it clean and an working on getting it patched up with some JB Weld.

The AF cover had been modified for improve flow.

View attachment 873633

If I can't locate a keyed clutch I will cut the ears off this one from a RH start saw.

View attachment 873634

I will need to rebuild a different fuel cap, this one is used when I am cleaning out a fuel tank with the BB's by rotating it slowly in the lathe.

View attachment 873635

I already located an oil cap, manual oiler works but I haven't been able to confirm the automatic oiler works yet.

View attachment 873636

The clutch cover had a hole in the back that I have already patched with JB Weld, and this crack. I will paint it and use it as is until I find a better one.

View attachment 873637

I have a few more pieces in this box plus a few more boxes that I have already taken over to the new building.

View attachment 873638

This shroud is in much better condition than the one currently on the saw so I will change it out.

View attachment 873639

This is the lower brace that was badly corroded, currently undergoing JB Rehab.

View attachment 873640

The saw starts well, idles nicely, revs responsively, and generally sounds good. I thought I'd measured the compression at 90 PSI but I can assure you it is much higher than that now that I've run it a bit. I will add one of my steel full wrap handle bars and use 3D printed clamps when the time come.

Mark

I have a chain cover that is cracked in a similar fashion. Have you tried those low temperature welding rods on something like this? If so how did it work?

Brian

 

[heimannm]

I have only used the "aluminum brazing" material on some lighter gauge stuff like handles with cracks or holes worn in them. I was thinking of applying JB Weld on the inside, maybe pressing a piece of wire screen or hardware cloth to add some reinforcement but I need to confirm there is clearance for the extra material.

Mark

 

[Maintenance supervisor]

Got started on the tank swap today. Getting the tank off of the G-70 was a straightforward yet frustrating process. Once I started digging into it I realized just how completely filthy the saw is, especially the area between the main body of the saw and the gear case... I have no clue where to begin on getting that spot clean lol.
To make matters worse there's this weird thick grey grease everywhere. It appears to have been applied mainly to the pull rope mechanism, but it's also present on a lot of the screws like it's some sort of threadlocker.
Despite my best efforts to avoid doing so, some gunk broke off and fell into the intake where its resting on the side of the piston. I got most of out out but some small specs of it fell deeper in where it's hard to reach. Is there a good way to flush that out somehow, or do I need to split it in half now to clean it properly? I was hoping to avoid that for now.
View attachment 873642
Beyond that, I did a test fit of the upper half of the G-70's fuel tank on the 10-10A lower half that I was hoping to use. It appears to fit great, and thankfully the top plate thingy from the Tillotson carb fits right onto the SDC, so the air filter cover screws on tight like it should. I think the all-yellow look is pretty cool too.
View attachment 873643
View attachment 873644
View attachment 873645
View attachment 873646
View attachment 873647
The only issue I could find is that there doesn't appear to be any thread on the two holes seen at the bottom here. I don't know if they're covered up by paint or if they just weren't used on this 10-10. Thoughts?
By the way, I'm not sure if this is even an original McCulloch fuel cap or not, but do you put a new rubber check valve in this like the normal plain square McCulloch fuel cap? I'm not exactly sure what's going on with the metal tab here.
View attachment 873641

The duck bill valve can be changed in that cap like normal.

 

[heimannm]

I just put that cap together with the screw so I could use it when cleaning out tanks, I fill the tanks 1/2 full of BB's then let them rotate slowly in the lathe for about an hour in each direction. I have other caps that I can refit with new duck bill valves. I even made a special fixture to support cap when replacing the sintered metal screen after knocking a hole in a couple of caps trying to get them to seal properly.

Mark

 

[Maintenance supervisor]

I have only used the "aluminum brazing" material on some lighter gauge stuff like handles with cracks or holes worn in them. I was thinking of applying JB Weld on the inside, maybe pressing a piece of wire screen or hardware cloth to add some reinforcement but I need to confirm there is clearance for the extra material.

Mark

I knew someone who made knifes with tree burl handles, he told me that they're inherently prone to cracking. The secret to his making the strong was building a simple vacuum chamber (large glass jug) for the epoxy to cure in. I guess it makes it very dense / no microscopic bubbles.
This is one of the handles with a slight blue color epoxy.

 

[vinnywv]

Got started on the tank swap today. Getting the tank off of the G-70 was a straightforward yet frustrating process. Once I started digging into it I realized just how completely filthy the saw is, especially the area between the main body of the saw and the gear case... I have no clue where to begin on getting that spot clean lol.
To make matters worse there's this weird thick grey grease everywhere. It appears to have been applied mainly to the pull rope mechanism, but it's also present on a lot of the screws like it's some sort of threadlocker.
Despite my best efforts to avoid doing so, some gunk broke off and fell into the intake where its resting on the side of the piston. I got most of out out but some small specs of it fell deeper in where it's hard to reach. Is there a good way to flush that out somehow, or do I need to split it in half now to clean it properly? I was hoping to avoid that for now.
View attachment 873642
Beyond that, I did a test fit of the upper half of the G-70's fuel tank on the 10-10A lower half that I was hoping to use. It appears to fit great, and thankfully the top plate thingy from the Tillotson carb fits right onto the SDC, so the air filter cover screws on tight like it should. I think the all-yellow look is pretty cool too.
View attachment 873643
View attachment 873644
View attachment 873645
View attachment 873646
View attachment 873647
The only issue I could find is that there doesn't appear to be any thread on the two holes seen at the bottom here. I don't know if they're covered up by paint or if they just weren't used on this 10-10. Thoughts?
By the way, I'm not sure if this is even an original McCulloch fuel cap or not, but do you put a new rubber check valve in this like the normal plain square McCulloch fuel cap? I'm not exactly sure what's going on with the metal tab here.
View attachment 873641

Your fuel cap question is answered. The 2 holes at some point were threaded. Might try a bit of a larger screw maybe metric so its just bigger. Or tap them. They help with vibration and leaking at the back of the tank.

I have to agree that saw is filthy. And yes the all yelliw have a good look i swapped out the tank on my 6-10 this year for an all yelliw tank. The carburetor just was too finicky. Put on a 10-10 tank and tilly fixed jet carb. World of difference in it. Runs very very well now. And it looks good all yellow. Just needs a 6-10 air filter cover to be right. It wears a 7-10 sticker now. I could make it a very early 7-10 with a LH starter and different clutch cover pretty easy. But it adds weight and takes away from what it is too much so it will stay that way until i find a 6-10 sticker. That gear saw is going great. Really enjoy reading your progress.

 

[Woodslasher]

Somebody better jump on this! @Jay Hansen

 

[Woodslasher]

@John Lyngdal

 

[John Lyngdal]

I saw that ad earlier today.
So many projects, so little time.

 

[McCullochKid]

I think I may have discovered why I thought the G-70 had less compression than I expected...
While using a Q-tip to carefully pick out the junk that fell on the side of the piston, I quickly became aware that the gentle pressure of that is enough to slightly rotate and rock the piston side to side inside of the cylinder, creating a nice clunking sound each time you do it.
Any ideas what's going on here? Is it toast? Seems kind of odd that there's that much play yet it's still able to run(off of a prime at least).

 

[Jethro 2t sniffer]

I think I may have discovered why I thought the G-70 had less compression than I expected...
While using a Q-tip to carefully pick out the junk that fell on the side of the piston, I quickly became aware that the gentle pressure of that is enough to slightly rotate and rock the piston side to side inside of the cylinder, creating a nice clunking sound each time you do it.
Any ideas what's going on here? Is it toast? Seems kind of odd that there's that much play yet it's still able to run(off of a prime at least).

Rings still working their magic. A piston will wear away getting looser in the bore it starts to hurt the bore eventually. Piston slap

 

[vizette]

I have only used the "aluminum brazing" material on some lighter gauge stuff like handles with cracks or holes worn in them. I was thinking of applying JB Weld on the inside, maybe pressing a piece of wire screen or hardware cloth to add some reinforcement but I need to confirm there is clearance for the extra material.

Mark

Project Farm did a good review of these; melting temp, holding strength, etc... If I remember, Bernzomatic rods rated well in his review, and surprisingly, the ones from Horror Freight.

I've used them a couple times (I want say mine are Alumiweld rods - had them laying around for like 20 years) and they are amazing, but you have to get the part really clean, and REALLY hot. I repaired a cylinder with one, but I had to get on it with a small oxy/mapp torch to get it hot enough since a cylinder is basically a big heat sink. Also patched up an XL12 handle that ripped open at the bottom bolt holes, but was able to get away with just MAPP on that one. I couldn't tell what was rod and what was original aluminum when I filed down the excess.

I'm definitely a fan of JB, but I wouldn't hesitate to use a rod on that clutch cover just for the overall strength vs JB in an obviously stressed area. I would definitely get in there prior though and open that crack up, just like you would if you were to TIG it. If the crack is all the way through, all the better - cut that crack open all the way through with an abrasive disk (e.g. dremel) and fill it back in.

 

[Brian Thacker]

I think I am going to try that. I will let you all know how it works out.

Brian