MCCULLOCH The official McCulloch thread

[Maintenance Chief]

I had the 73 together last week only to discover a crack in the gearcase cover that was weeping oil.

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Took the saw apart, cleaned the cover thoroughly and applied some J B Weld to the inside, back together and at least that leak was cured. Still weeps a little around the starter cover and now the primer is dripping a bit.

At least it was running again, much like before though with good top end but won't continue to run at idle.

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Mark

If you were actually going to run this beast at say gtg's or such ,how hatd would it be to convert it to say a tillotson from an 090 or something?
Just wondering.

 

[heimannm]

Not really possible. The early saws were rotary valve, and the carburetor was built in to the handle/frame of the saw. The throttle is a sliding gate built into the side of the saw, the "venturi" of the carburetor is also the hole for the air filter, the high speed needle is built into the top of the rear handle, and the metering system and low speed adjustment are built into the only carburetor body that detatches from the saw.

The big hole is for the air filter, and that portion also makes up the venturi. The metering body with the low speed adjust attaches below.



The high speed needle is in the handle portion. That long lever allow you to adjust the H setting with the saw in operation.



You can see the high speed needle passing through the side of the venturi chamber. At the bottom of the venturi chamber you can just about see the throttle gate in the 5:00 position.



I will try to add some photos of the metering chamber with the low speed adjust later on.

Mark

 

[heimannm]

Here is the metering portion of the carburetor with the low speed adjust (mounted below the venturi). There are two lines from the fuel tank, one suppy and one return and the nipples are even color coded on the fuel pump and the metering body so you can't get it wrong. Black for supply and silver for return.



As noted, the early saws were rotary valve design, here is the side of a 3-25 with the rotary valve and throttle gate removed.



Rotary valve and throttle gate installed.



Cover over the rotary valve and throttle gate installed. Here you can see the crankshaft is rotate to open the valve, throttle is closed.



Crankshaft rotated to close the valve, throttle closed.



The air/fuel mixture passes through the venturi, past the throttle gate, and makes a 180° turn to go into the crankcase.

Mark

 

[heimannm]

Finally, the cover over the throttle is installed sealing the system.



"Best technology available"...at the time.

Mark

 

[jacob j.]

Finally, the cover over the throttle is installed sealing the system.

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"Best technology available"...at the time.

Mark

McCulloch's engineering was amazing for the time. The CP saws were game-changers for sure and other companies adopted many of McCulloch's engineering ideas. Using a rotary valve on a chainsaw in the mid-50's was a pretty wild idea.

 

[edju1958]

Great news- I finally got the pesky Super 10-10 put together with the carb on today.I swapped everything off the saw ontop a different short block & it runs great now.Only thing is I'm not quite happy how it oils.It does oil,but not like it should,a little on the skimpy side.

 

[edju1958]

On yet another note.....I received the PM605 today that I bought 2 weeks ago.The front handle & part of the rear handle were bleached white from sitting in the sun.I thought I'd have my hands full with this saw.I took the chain brake off & cleaned out the hardened sludge,pulled the plug out - it looked to be a fairly new Champion DJ8J & put a prime in it & put the plug back in.I didn't expect much,but it fired.Next I tried to get the fuel filter out to have a look,but it was so big I couldn't get it out of the tank.I figurerd screw it & put fuel in & had the saw ruinning in 3-4 pulls.Had to step the idle up a bit.I couldn't believe the saw ran! There is an issue with the manual oiler - the button wants to stick.I don't know if someone bent the rod,or if it's not the correct rod.I've had an incorrect oiler rod on a PM610 recently.I'll check it out more tomorrow & should have some pics as well.




Ed

 

[Al Smith]

That 73 or 76 my uncle had was heavy when I was 16 years old and at 35 it hadn't lost any weight .That thing had a steel cable for a start cord .

 

[heimannm]

That is "wire rope" Al, don't want to upset Carl...

New project on the bench this afternoon. Can you guess what it is?









I went through the primer on the 73 again today and believe I have the leak stopped, or at least slowed to the point I can ignore it. Seems my son forgot an o-ring when he put the new seal and packing in on Saturday.

Mark

 

[edju1958]

Mark,I'd have to say it's something to do with McCulloch,Lol.

 

[farminkarman]

That is "wire rope" Al, don't want to upset Carl...

New project on the bench this afternoon. Can you guess what it is?

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I went through the primer on the 73 again today and believe I have the leak stopped, or at least slowed to the point I can ignore it. Seems my son forgot an o-ring when he put the new seal and packing in on Saturday.

Mark

No, but it looks big.

 

[edju1958]

I found the problem with the PM605 oiler rod issue.It seems that the PO had decided to pull it out for some reason & put it back in sideways causing it to bind.Put it back in the correct way & it works great now.

 

[Woodslasher]

797L if I see the tag right.

 

[Al Smith]

I never really knew much about uncle Chucks big old gear drive .Quite frankly I didn't know nearly as much back then as in later in life .It had either a 30" or a 36" bar and must have had a governor because it didn't wind up that fast .That said unless you were gorrila strong you could not stall it .At that time good old bull headed unc Chuck had a little Homelite he carried around in a 5 gallon bucket .TSC special $89.95 .

 

[Dream]

That is "wire rope" Al, don't want to upset Carl...

New project on the bench this afternoon. Can you guess what it is?

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I went through the primer on the 73 again today and believe I have the leak stopped, or at least slowed to the point I can ignore it. Seems my son forgot an o-ring when he put the new seal and packing in on Saturday.

Mark

The correct term is "wire rope".
A steel cable is a different construction, and meant for a different purpose.
This is coming from an overhead bridge crane technician with 31 years experience to date.
Id be more than happy to explain the difference, just not here, so PM me for that.
On the new project, its definitely a large frame saw.
I'm learning more as time and experience permit.
It has the same basic outline as a 797/125 series saw, but I cant offer any further observation.

It's a "Redwood killer". Thats all I know.

 

[heimannm]

No AV and the front mounted pulse oiler tell you this is a 795L. I've heard that there were some 797L models produced as well but I've never seen any documents that would confirm it.

I'm not sure but I think the clutch cover was only found on the 795L and some PM105 models. Of course, the IPL's for those two models reference different part numbers and appear to be different.

Mark

 

[heimannm]

795L is cleaned up and has been moved into the display.







Mark

 

[heimannm]

Next challenge is this 1-75 with multiple issues. I have a 1-85 that is an outstanding performer so I really want to get this one running and make some test cuts.









Start with a little tear down for cleaning and inspection.



Mark

 

[heimannm]

I think I've uncovered the reason for the low compression...



Second ring on top of the first.



Rings were also somewhat stuck in the grooves, most likely due to setting in the PNW for too long.





Mark

 

[heimannm]

I ended up using +0.030 rings. In spite of the bore being standard size (2.124) the new standard rings had a gap of over 0.025" (no locating pins on these pistons) so the ring end filer came into play.



I did run into a few other issues along the way that held up reassembly but I am making progress.





Mark