McCulloch Chain Saws

[bob kern]

7-55 going back together. The 7-55 like many of the early McCulloch saws has a rotary valve for the intake.

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As the crankshaft rotates the valve opens a passageway into the crankcase.

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Cage for the needle bearings and needles stuck to the crankshaft with a little dab of grease.

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If you work carefully, you can stick the rod cap in place as well.

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Make sure the pips on the rod and cap line up.

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The points are external so there is a pushrod that rides a cam on the crankshaft.

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The early model two man saws featured some counterbalance weights to help reduce the vibrations.

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Crankshaft seals have been replaced, but now I have a leak around the counterweight cover. I may have to use some Dirko on the gasket and mating surfaces. I do have a nice strong spark.

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Mark

Once again , excellent info Mark! Thanks.
I got a saw going for the boyfriend of a former employee this evening. Of course I steered the conversation to old macs. He said he has one in his shop that leaked oil so bad he never used it. I believe from the description it may be a 1-75. I pulled up a pic and he's 99 percent sure that's what it is. Says he has a case and all. It will be interesting to see if it's a home made case or a factory issue one. Wouldn't that be something!

 

[MacAttack]

Mark's 7-55 project inspired me to have a look at my 4-30. The saw seems very complete but the recoil is all kinds of messed up. Initial observations include compression is way down and main bearings have some play...this saw might always just be a conversation piece.

I can honestly say I've never been more confused by a recoil. It was bound up pretty bad due to some kind of bizarre spring/bushing thing being deformed. The recoil spring is broken, and unless I'm crazy the crank seal is actually in the recoil housing???

 

[heimannm]

That flat ground spring is an overrunning clutch for the starter, grips the starter shaft in one direction to pull the engine over and slips in the other direction so it doesn't pull the rope back in if the engine kicks backwards. That spring is definitely out of service. I probably have one if you ever decide to try and make the saw run again.

The clutch is running in the gearbox oil so the seal in the starter is to prevent the oil from leaking out. There is another seal in the crankcase behind the gearbox.

Mark

 

[MacAttack]

Thanks Mark... I will have to decide if it's worth the time, effort and expense. I would guess a 4-30 isn't exactly a fast cutting saw haha.

Right now I'm focused on the 450, waiting for my piston / cylinder / crank assembly to arrive.

 

[heimannm]

A healthy 73 will stomp a 450 if you can handle the saw.



This is a 77 but the displacement is the same. The 77 has a different carburetor set up but the engines are pretty similar.

Mark

 

[bob kern]

Was someone looking for a yellow tank Mac 15?
It's in Illinois

 

[MacAttack]

A healthy 73 will stomp a 450 if you can handle the saw.

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This is a 77 but the displacement is the same. The 77 has a different carburetor set up but the engines are pretty similar.

Mark

I just realized Mark.... my old 50's McCulloch is actually a 4-30, 87cc, not a 73. So now it makes sense that a 7-30 would spank a 450, it's a 120cc saw! I fixed my typo in my other posts.

Maybe I'll have to tear into it when time allows though, thanks!

 

[MacAttack]

Got the piston / crank / cylinder assy today for my 450 project. It looks very nice, bearings feel smooth even. The reed block insulator even looks intact. (New one on the right side)

 

[Jeffrey F.]

Got the piston / crank / cylinder assy today for my 450 project. It looks very nice, bearings feel smooth even. The reed block insulator even looks intact. (New one on the right side)

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Very nice !

 

[heimannm]

I spent an inordinate amount of time on the primer and oil pump(s) yesterday.

On the primer, I tapped the plunger 8-32 and use my old cheapo WalMart slide hammer to pull the pump apart. This is the orientation of the primer on the saw, fuel enters the lower port (red) and is pushed up into the carburetor (red port) when the spring returns the plunger. The cup seal is 24104 and the o-ring is a 010. I was able to reuse the felt seal/packing, the ring holds the felt in place.



It is important to get the gland pressed back into the proper position so I made a little guide from a piece of tubing I had on hand. If you look carefully you can see the groove and the hole in the gland aligned with the outlet port.




These is another disk with a hole and a small check ball at the very bottom of the primer but I did not have to remove them on this one.



The manual oil pump is a pretty simple affair.



If you press the plug on the end the pin will come out releasing the plug.



At that point the whole plunger can be pushed out.



Again, the o-ring is a 010 and the cup seal is 24104.

To access the felt seal/packing in the other end of the pump you have to remove the washer. On some, the stake marks are pretty light and you can just pry it out. On others it may be necessary to drive a bit of material back from the edges.





Here you can see the felt seal/packing and washer, there is also a 010 o-ring at the bottom of the gland.



Apparently I forgot to take any photos but I replaced the felt with bushing made from UHMW PE with an o-ring on either end.

Good news is with new cup seals installed, the oil pump is working. Bad news was the original oil pump from this saw (brass plunger in the photos) was so badly worn I had to rebuild a second pump from a parts saw on hand to be sure the rod that drives the pump won't fall out...

Mark

 

[heimannm]

The fuel lines and oil lines are often in bad shape on these old saws. That is a "complete" line attached to this tank, and what was left of the fuel line on this current 7-55 project laying on the tank.



I was able to clean most of the old line out of the banjo fitting, and expanded the brass a bit with a hollow punch to allow me to use a piece of modern fuel line material for this saw. The fitting in the tank is standard 1/8" pipe, but the banjo fitting is a sort of inverted compression fitting. Because of the way the fuel line attaches to the carburetor, you really need to use the banjo fitting.





Mark

 

[MacAttack]

Great work Mark, your rebuilds have got to be the pinnacle of vintage McCulloch restoration, haha.

 

[flatsfisher]

PM1000 disassembled for final cleaning, then paint removal of parts to be repainted.

 

[MacAttack]

This saw is just filthy.... I got the phenolic disc and pump shaft out of the oil pump, I have PB blaster soaking it. I'm crossing my fingers that it works, especially if it has one of those tiny check balls like in a Mini Mac.
I will also need to clean up the bore for the disc and hopefully get it moving smoothly again.

Slow and steady on this rebuild....

 

[heimannm]

Stop switch needed repaired. Clamp it in the vise and spread the tabs.



Those tabs are supposed to be attached to the base of the switch as contacts.



That worked.



Not pretty but it worked. The switch above (from this 7-55 project) is externally grounded to the case.

This switch from an earlier project saw was grounded internally through a third contact.



Mark

 

[heimannm]

Carburetor rebuild is normally required. Jeff Fox (cinci5) makes these gaskets and diaphragms and supplies hollow rivets so you can swap the metal plates from the old to the new.

Drill out the rivets, clean up the plates, and attach them to the new diaphragm. I use some LocTite 380 around the rivets to be sure they are sealed, around the perimeter of the plates to keep them attached, and at the gaskets to keep the assembly together.



Jeff made this template for me and I assembled the base of this jig to aid in keeping the assembly in proper alignment as the LocTite sets up.





24945 is the diaphragm used with the later carburetor with the fuel channel. Earlier models did not have the fuel channel and used a different diaphragm (18199).

Fuel channel on the left, no fuel channel on the right.



For this 7-55 project I took the carburetor completely apart for cleaning and inspection.



I had some trouble getting the fuel to enter the carburetor on this one. It would run on the primer (pulls fuel from the fuel bowl) but would not pass fuel through the carburetor. I continued to disassemble and re-adjust the metering lever until I got it to operate decently. I have never had to do this on my previous 3 or 4 saws.

Mark

 

[heimannm]

Just a note for any of you working on a two man McCulloch saw, if you install the clutch, also install the transmission when you test run the engine...or be stupid like me and wonder why the saw seems to be under load when you accelerate it. Once I installed a "test" transmission and adjusted the throttle cable I was able to get the saw to operate almost normally.





Mark

 

[flatsfisher]

saw a MAC battery charger on marketplace. looked like a 10-10.

 

[MacAttack]

It ain't pretty.... but after an hour with a Dremel and various brushes and abrasives, I got the oil pump diaphragm bore cleaned up and when I operate the pump it appears to work!

This is by far the dirtiest and most corroded Mac I've ever worked on. And they say a Mini Mac is hard to work on??? Hahahaha... give me a Mini Mac any day over this front tank Frankenstein of a saw.

 

[Rotax Steve]

saw a MAC battery charger on marketplace. looked like a 10-10.

Those I've seen before. I believe the charger is an attachment you install like you do with the bar and chain. The one I saw was also on a 10-10 and if I remember right I don't think it was a McCulloch accessory? Don't know if they were made for other models or brands?