Mcculloch 850 Pro Mac build.

[Warped5]

TJ, sent you a PM ...

 

[PogoInTheWoods]

Sub'd...

 

[Al Smith]

For that matter unless the cylinder is gouged more than likely it will clean up .Easy off oven cleaner and 3M green pad,elbow grease .
I've never tried Randy's method with a pad on a mandrel but the next one I do I'm going to give it a go .

 

[Al Smith]

Now this piston business has got me interested in thinking about reviving the 850 I have residing in a box in my shed .I happened to find several used piston but noticed a new aftermarket sold by I think little red barn .It's listed as a B size by part number ,doesn't have the bearings which really aren't a problem to find .I wonder if it's worth the effort to try it out .
From what I understand the pin is a press fit in the rod which I suppose would take some heat on the pin end of the rod and a press of some sort or a pull bolt contraption . It would make sense the needle bearing cages would also be some kind of a press fit .Uncharted territory .I've never had a rod off a ten series piston assembly or any McCulloch for that matter .

 

[Steve]

The Mac service manual says to heat the rod to 200 degrees and lube the pin with engine oil and press it on with a press. It also states to not reuse the pin bearings in the piston once pressed out. I put the rod in a pot of boiling water for a few minutes and then press the pin in with a few sockets. I would just get a Mac piston from cheapchainsawparts for 50 bucks. I bet the rod bearing and the lil red barn piston cost more.

 

[Sleeper]

Now this piston business has got me interested in thinking about reviving the 850 I have residing in a box in my shed .I happened to find several used piston but noticed a new aftermarket sold by I think little red barn .It's listed as a B size by part number ,doesn't have the bearings which really aren't a problem to find .I wonder if it's worth the effort to try it out .
From what I understand the pin is a press fit in the rod which I suppose would take some heat on the pin end of the rod and a press of some sort or a pull bolt contraption . It would make sense the needle bearing cages would also be some kind of a press fit .Uncharted territory .I've never had a rod off a ten series piston assembly or any McCulloch for that matter .

For getting the pin out, an arbor press works well. I bought one at HF, a 1 ton model. Made a block out of pine 2x4's cut about 4" long, stacked them and screwed them together, when grooved out, that surrounds the piston and fits snug to it. Then a hole drilled in the middle for the pin. Used a socket that was just under the size of the pin and put a pipe on the lever and pressed it out. You will need to clamp the press to the workbench with C-clamps... and this was on a 790 piston/connecting rod assembly. I did not use any heat. Just some penetrating oil.

I'd be wary of using heat from anything but a hair dryer, heat gun, or propane torch. No oxy/fuel torches... if you change the temper of the connecting rod, you're screwed and it will likely come apart later. At least, that's what my engineering portion of my brain says.

 

[Warped5]

I did something like that. Plus used a little heat and tap tap tap. went very smooth.

I'm not going into details, but I don't trust Lil Red Barn as far as I can spit.

 

[Al Smith]

So the rod is bushed? Because it's pressed fit I would assume it be heat shrink captive like automobiles used to be .
That's a story,they all used to bushed rods with circlips then they decided to use heat shrink,no bushing .Now of days it is a bushed rod with circlips once again .They came full circle so to speak .

 

[Al Smith]

In thinking this over I have heat gun,good one,"Varitemp" 1000 degree industrial .Very similar to what is used in automotive engine plant Thinking out loud you could probably press the pin out but it would take some heat to reassemble .Freeze the pin heat the rod end perhaps .As far as those needle bearings I've seen them from 9 bucks a pop to two for 12 bucks .For that matter it's probably a standard needle bearing a person could get at Bearings Inc,Dixie or some other bearing house . It's mac # 11590 which coincidentally is the same as a 700 bearing .

 

[Steve]

No bushing in the rod. If I remember correctly the pin bearings are Torrington BH-108.

 

[TJ the Chainsaw Mechanic]

I think 42" is overly optimistic, 36" seems max to me and mine wear and are happy with their 32" bars. I just ran them both in a piece of old growth fir last weekend. 850's are smooooth (895's are definitely not) for sure. Mac sure had rubber AV down well, better than Stihl IMHO.

One of my co workers said they used to run 42's on them....must have only been in soft wood. I'll probably end up with 36" Oregon light bar or something other.

 

[Adirondackstihl]

I'd run a 28"-32" on it if it were me

 

[exSW]

When I put mine back together I just left the piston outside for a while. It was -14*F at the time.

 

[TJ the Chainsaw Mechanic]

When I put mine back together I just left the piston outside for a while. It was -14*F at the time.

Lowest temps here currently have been +55 lol

 

[Al Smith]

If you are looking for a new McCulloch bar I doubt you'd find one over 32" . With perhaps a little rework I think a Husqvarna mount might work . I know some will and some won't depends on who made them .
On the PM 1000 which is a Partner p-100 if you use the McCulloch bar plates a mac bar will work .If you use bar plates for a 2100 Husqvarna the Husky bars fit .What plates other than McCullochs might fit I have no idea on an 850 .

 

[backhoelover]

you should be getting the service manual in a pm tj . if anyone else wants a pdf copy just send me a pm. i bought several mac binder with alot of manual we dont have in pdf but you have to break the binder it get manual out i think

 

[Warped5]

Custom Chainsaw Parts on eBay has had some really good deals on 36" OEM b/c combos .... IIRC, I got one for $48 + shipping

 

[TJ the Chainsaw Mechanic]

Update all....new piston with rings, bearings, wrist pin and con rod all on the way. Thanks Steve!
Also off ebay I was able to order new crank seals, fuel line, impulse hose, and an intake boot. All nos minus the two seals. Getting excited guys. Gonna take the cylinder in and hone and emry cloth it and hope it'll clean up. If not...search stays on for another B cylinder.

 

[jockeydeuce]

Builds like this are the most fun...
.Document as much as you can along the way. I like seeing the vintage muscle saws brought back to life.

 

[TJ the Chainsaw Mechanic]

Started painting some parts and choices of color.