Mcculloch Pro Mac 850

[BrushMonkey]

Hello all,

Saved a PM 850 from the scrap pile. Was at a Steam Show and this saw was in the parts/repair bin for $10. Seller threw 2 other mccullochs away but decided to sell this one.... Pulled on the yarn and it had more than enough compression to run, at that point I was a buyer.

Well now it's running and cutting wood. Basic carb clean & new fuel is all it took.

Piston has some scuffing on intake side. Enough to catch my nail, haven't checked exhaust yet. SO here's where I need help. Where to find pistons/cylinder for this saw? Bar dogs? Compression release or delete (it's oilely and likely leaking)?

I know zero about mccullochs so shed some light on this old workhorse for me. I'll be keeping it and putting it to work as a bucking saw.

 

[rwoods]

BrushMonkey, welcome to AS. You will get more responses if you post your MAC questions on the McCulloch stickie thread. There will be a lot of envious but helpful folks there. The PM850 is a big favorite of the MAC folks.

Ron

 

[Mad3400]

You can a find a new Piston & Jug, Gaskets and Seals off "Lil' Red Barn".

Felling dog on eBay.

And do a Decomp. Delete.


Hope this helps,

Mad3400

 

[Rallyeguy]

Hello all,

Saved a PM 850 from the scrap pile. Was at a Steam Show and this saw was in the parts/repair bin for $10. Seller threw 2 other mccullochs away but decided to sell this one.... Pulled on the yarn and it had more than enough compression to run, at that point I was a buyer.

Well now it's running and cutting wood. Basic carb clean & new fuel is all it took.

Piston has some scuffing on intake side. Enough to catch my nail, haven't checked exhaust yet. SO here's where I need help. Where to find pistons/cylinder for this saw? Bar dogs? Compression release or delete (it's oilely and likely leaking)?

I know zero about mccullochs so shed some light on this old workhorse for me. I'll be keeping it and putting it to work as a bucking saw.

Help for parts:

Gasket kits I make at www.oldsawshop.com https://www.arboristsite.com/members/rallyeguy.158926/
Lots of oem parts Mark Heimann [email protected] https://www.arboristsite.com/members/heimannm.8552/
Lots of oem parts Max Rowe https://www.arboristsite.com/members/knightmax.170890/

 

[Woodslasher]

I wouldn't recommend Lil Red Barn stuff, but I believe @vinnywv has a guy who will bore and sleeve those cylinders.

 

[heimannm]

I've seen the starter housing broken off 82cc McCulloch saws when the compression release is not used. Just ask JoeyMT.

Mark

 

[BrushMonkey]

Are other 82cc mac cylinders interchangeable? There's a pro mac 800 parts saw for sale locally

 

[knightmax]

Some
Parts of the PM800 are. From the PM800 forward they changed the blocks, clutch covers, recoil covers and a few other things. Crank is shorter. Pistons, rings, rod, bearings, seals, gaskets, and fuel tank same.

 

[knightmax]

And mufflers changed.

SP80,81,and PM850. All basically same parts. Change I mentioned above started in the PM800

 

[knightmax]

You can a find a new Piston & Jug, Gaskets and Seals off "Lil' Red Barn".

Felling dog on eBay.

And do a Decomp. Delete.


Hope this helps,

Mad3400

I would not recommend LRB pistons. They have created many issues.

I would also make sure the cylinder is a Qport if doing a decomp delete.

 

[Squareground3691]

And mufflers changed.

SP80,81,and PM850. All basically same parts. Change I mentioned above started in the PM800

Yea , changed the muffler on my 800 witch is a total joke , over to a 850 muffler,

 

[BrushMonkey]

Tools, parts and pieces are slowly trickling in by snail mail. For my own OCD I wanted to get base numbers of this saw before any changes. Comp test tells me to run the saw as is but still waiting on a mittyvac to test the seals.
Cold psi was 158 with decomp valve installed, which surprised me with the damaged piston although all the nicks were below the rings.

This was with the echo compression tester. tested my other saws for comparison.
Pm 850 158psi
066 155psi
046 138psi (new piston & rings)
261 168psi

Now all of these still have decomps installed and the 046 has little run time since new piston and rings. Unknown run time on the 3 older saws. 261 I bought new 4 years ago.

 

[knightmax]

158 is good. Run it. Store the extra parts. They are not making anymore of them,

 

[Jethro 2t sniffer]

Are other 82cc mac cylinders interchangeable? There's a pro mac 800 parts saw for sale locally

Grab that 800 also if price is good

 

[Syncop8r]

Grab that 800 also if price is good

And send to either of us.

 

[Jethro 2t sniffer]

And send to either of us.

Yeah you do really need 1