Mcculloch Pro mac 850

[Terrence Jefferson]

Just got this beauty going but it sounds like the decompression is presses in when it isn't. I swapped it for another one from the 7-10 i haveand same thing. So i did some looking and found this. Is this supposed to be like this or do i need to find a new cylinder?

 

[Terrence Jefferson]

That is looking through the decompression hole. If anyone has any info that would be helpful. Thank you

 

[Terrence Jefferson]

Ive been looking for any info i can find on this and i cant find anything. Im thinking this might be an oops from its younger days and im ok with that i just would like to plug it all up if i can. Does anybody know if they makeor made a decompression plug for this saw ? My searches will continue but if you have any help that would be great.

 

[Czed]

@p61 western
@beaglebriar
@Stump Shot
Thoughts?
I never ran macs

 

[Dub11]

@heimannm
@Lee H

 

[Steve]

The sealing surface looks real dirty. Clean it off real well and recheck with soapy water to check for leaks.

Or is that pitting? If its pitted then clean the treads on the valve and the cylinder real well of oil and use some high temp red rtv or dirko on the threads. Just enough to seal it. Dont get it in the valve.

 

[Terrence Jefferson]

Steve if you look closely at the picture tjat hole is light on the nack side of where the decomp goes. I did spray it with soapy water and only got bubbles out of that hole. Im not sure if someone drilled this hole or what but i hope to fix this cause what little i did get to tun it seems like it might be my new favorite saw.

 

[Steve]

Okay, so you have a cylinder drilled and taped for different decomp locations. The 850 decomp should be in the top of the cylinder. The hole where the flashlight is, is used on the pm800/805. The 800s use the decomp as a bolt for the muffler bracket.

I would just put the decomp wherever it threads in and plug the other with a bolt.

 

[heimannm]

I had one that wouldn't seal so I set it up in the mill drill and spot faced the seat for the compression release valve.



The socket head screw just above the muffler is there to allow you to clean out the port into the cylinder. 10-24 x 1/4"



Mark

 

[Terrence Jefferson]

Thanks guys but my picture is not showing where the hole actually is. The hole you can see is on the backside of the decomp hole. Its like its drilled all the way through and the screw is in the clean out hole this is on the backside of the decomp port between the fins on the cylinder.

 

[Terrence Jefferson]

Mark if you look at your last picture the area between the clean out screw and the next fin towards the bar is where my cylinder has a hole. You can see a little bump or something on your cylinder if you blow it up.

 

[Terrence Jefferson]

 

[Steve]

Thanks guys but my picture is not showing where the hole actually is. The hole you can see is on the backside of the decomp hole. Its like its drilled all the way through and the screw is in the clean out hole this is on the backside of the decomp port between the fins on the cylinder.

Ok. Like somebody drilled too far. Got it. Let me go home and look at a cylinder i have and come up with an idea.

 

[Terrence Jefferson]

Yes steve. Im kinda lost. I would just plug it but im not sure what to fill the hole with.