Rebuilding a Mcculloch 850 ... questions

[heff17]

Here is the back story.. I scored a Mcculloch 850 non running and thought it just needed a carb rebuild. Evidently it was run with straight gas and the piston is gone. I've been partial to Mcculloch since my dad ran a 610 and heated our house with firewood and really want to fix this saw. I do not believe the cylinder is un-repairable needs to be cleaned with acid and probably honed. The cylinder and piston are both marked 'A' so my questions is should I run a 'B' piston after the cylinder is honed, or should I stick to the 'A' piston. It seems the 'A' piston is alot harder to find. I would love some guidance from anyone with knowledge of these 82cc saws!!!

 

[2broke2ride]

Check with the guys in the McCulloch sticky. But I can tell you that if that cylinder in chrome lined you do not want to put a hone to it. Use a scotch brite on a split mandrel to clean up any transfer. If it is scored badly it will need to be either replated or replaced.
My understanding is that an A cylinder has to use an A piston. Clearance would be too tight with a B piston.

 

[rwoods]

Agree with above. Also skip the acid. Too easy to ruin one of these cylinders. Unfortunately, I have. Ron

 

[rwoods]

Begin here: https://www.arboristsite.com/community/threads/mcculloch-chain-saws.71126/page-1393

Ron

 

[heff17]

Thanks for all if the advice! I've worked on the cylinder today after work. Got most of everything cleaned up. Even as bad as it looked the saw had 80lbs of compression before I tore it apart, but would not fire. Do y'all think she will run with a new piston and rings? It had great spark, new plug, and I've gone through the carb.

 

[rwoods]

On my little screen it looks pitted. Is it? BTW the true MAC experts hang out in the McCulloch sticky. Ron