Mcculloch 850 Pro Mac build.

[TJ the Chainsaw Mechanic]

Picked up this mac 850 for free last week. Been sitting for a Loooong time. Pulled it all apart and she'll do fine with a new piston, rings, and seals. Lot's of other things needed like tune up parts and hoses. Should be a fun project. Gonna paint it all up and make it look perrty to. Here in the West an 82 cc saw gets a long bar so.....having a hard time deciding between a 36 and 42. Already have a saw with a 36. Planning on doing some minor port work and a timing advance. Only picture as of now...I'll get more tomorrow.

 

[Warped5]

This will be fun to watch.

Let me know if you're looking for parts sources.

 

[Adirondackstihl]

 

[TJ the Chainsaw Mechanic]

This will be fun to watch.

Let me know if you're looking for parts sources.

Thanks! So far I've found pretty much all I need, just need to get the cylinder cleaned up so I can see what "series" it is...A,B,C, or D. Found a B on the crank but no letters on the cylinder yet.

 

[TJ the Chainsaw Mechanic]

Here's a picture of the scoring on the piston. Not horrible, but the rings are seized in there. Cylinder should be fine with a little emry cloth and honing. And a picture of the B on the crank.

 

[exSW]

I don't believe the "B" on the crank is what your looking for. Should be stamped on the top of the jug.

 

[Warped5]

I don't believe the "B" on the crank is what your looking for. Should be stamped on the top of the jug.

+1 ^^

Clean the piston and check it everywhere as well. IIRC, if there is no letter the default is 'B'

 

[sawfun]

Picked up this mac 850 for free last week. Been sitting for a Loooong time. Pulled it all apart and she'll do fine with a new piston, rings, and seals. Lot's of other things needed like tune up parts and hoses. Should be a fun project. Gonna paint it all up and make it look perrty to. Here in the West an 82 cc saw gets a long bar so.....having a hard time deciding between a 36 and 42. Already have a saw with a 36. Planning on doing some minor port work and a timing advance. Only picture as of now...I'll get more tomorrow. View attachment 83494

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.

 

[Steve]

My 850 has no stamp so it is a "b" cylinder. An 800 cylinder I have has a "b" stamped right on top of it.

 

[exSW]

I can't remember if mine had a "B" stamped on it or not. But it was a "B".

 

[Al Smith]

I heard they made up to 42" for the 850 size but I've never seen one .I'd imagine 32" or 36" is what you could find .However you'd stand a better chance in the PNW than you would in these parts .

 

[Al Smith]

You could get those rings off .A little work with an exacto knife,gently and they'll pop right out . That done get a thin fingernail file and work on the grooves . ..I've done several that way .
Push comes to shove you could probably save the piston .However you're going to need to go "old school" according to some and use a heavier mix ratio on the fuel .It won't hurt it ,might smoke a tad is all .Cut wood and fog for mosquitoes at the same time.multi tasking so to speak .---btw good luck

 

[Sleeper]

Oh, and regarding these... putting the piston back in the cylinder with rings on it can try your patience... need a dull pick to carefully press the ring into the ring groove with light pressure on the piston... it can be a PITA to get it to work. Don't use a sharp pointed pick or you might damage the ring.

Rings are available, but last I checked, they weren't cheap.

 

[Al Smith]

Unless the cylinder is really screwed up it's cut with a chamfer on the bottom .It's easy enough with the rod off the crankshaft but it can be a beech if it's still attached .It can be done either way but I prefer the former myself .

 

[Warped5]

+1^^

 

[TJ the Chainsaw Mechanic]

Found a B piston for $50 with rings. Gonna get that coming soon. No markings on the jug so I'm gonna assume a B series. Cylinder does has some transfer so I may just swap on another jug if I run across one.

 

[Steve]

Here is a pic of my "B" cylinder for reference.

 

[TJ the Chainsaw Mechanic]

Here is a pic of my "B" cylinder for reference.View attachment 83615

No marking there on mine....Wanna sell that cylindr? lol

 

[Steve]

No marking there on mine....Wanna sell that cylindr? lol

Can't. But I have everything else you may need.

 

[TJ the Chainsaw Mechanic]

This will be fun to watch.

Let me know if you're looking for parts sources.

Taking you up on that, You know where I could get a good B cylinder?