Pro Mac 800 do's and don'ts

[Jake Dykstra]

My buddy has a nice pro mac 800 and I runs really good! He wants me to port it up a bit for a little more speed.
Any absolute do not's on this saw?
Seems to have gobs of torque. I think just getting it to move air a little faster should bring the in cut rim up a bit.
No idea what it has for port timing. If you have a good recipe please share.
Any timing advance needed on this model?
Thanks In advance
Jake

 

[Stump Shot]

As a bit of history going back when these saws were made, the only people at the time that could make a really good plating job on a cylinder were the German's. McCulloch and everyone else at the time, struggled with this process making it stick. That said, there is some risk if you take away the portion of plating that is lapped over into the port, exposing the edge, it could peel possibly. Just thought you should know this going in. For myself, when I did my Pro Mac 700 which I love dearly by the way, I left the cylinder alone knowing this, as for me, its better to run as is than not at all. That doesn't mean that the outer part of the exhaust port for example can't be enlarged, the ports matched and detailed. Or, maybe it's worth it to you to port it out and get more out of it, I can't answer that for you, again, just for your knowledge is all, and I can't help with numbers and such as I haven't tried myself.
As far as ignition timing, 4 to 6 degrees advance should put it in a pretty sweet spot for making power. Also, make sure what's there is working properly and up to snuff, such as the carburetor diaphragms, air and fuel filters etc. allowing the saw to run its best, whatever path you choose for it.
Good luck,
Steve

 

[Maintenance Chief]

Change over the muffler to an 850 or SP81 . Or mod it.

 

[JimG.]

+1 on the muffler swap suggestion. The muffler on these is an odd design. If you dont mind more noise a simpler muffler will add a little performance. I advanced the timing on my 800 about 4 degrees. More than that and mine would tend to kick and pop.

 

[Stump Shot]

+1 on the muffler swap suggestion. The muffler on these is an odd design. If you dont mind more noise a simpler muffler will add a little performance. I advanced the timing on my 800 about 4 degrees. More than that and mine would tend to kick and pop.

That would make it around 32° total, which is a really good spot to be.

 

[Jake Dykstra]

Awesome gents. He really loves the saw so I'll probably muff it and port match and add a little timing.

 

[heimannm]

In reality the PM850 and/or SP80/81 mufflers will not actually just bolt up. The PM800 family use a strap on top of the muffler to support it to the cylinder, the PM850 and SP models have two tapped bosses on the side of the cylinder to support the muffler.

Yes, the port is the same size and shape and the mufflers will bolt on, but there is nothing further for support so take your chances.

If you want a saw to hot rod, you might be better off looking for something with more parts availability. New cylinders and pistons for the 82cc McCulloch saws are now in the $350-$450 range most of the time.

Much of this had been discussed recently. https://opeforum.com/threads/mcculloch-pro-mac-850-800.33981/

Mark