How much to remove

[camel2019]

I’ve been watching videos and the like on porting. From what I understand you use the degree wheel to figure out when the exhaust and intake ports open and close. but how do you know how much to take off to get to your goals? I want a mild woods ported saw that will breath better and live longer.

 

[Ronie]

Google, "threads/chainsaw-porting-thread-links.16583" You will probable get more inf on porting on the forum that comes up.

 

[Sepia]

The most accurate way is to use a piston ring. Find top-dead-center then remove the cylinder (after a good cleaning around the base) and remove the ring from the piston. Insert the ring into the cylinder part way (below the exhaust port). Make sure the piston is near bottom-dead-center then re-install the cylinder. Now rotate the crank slowly to the timing number you desire for either the exhaust port or the transfer ports. Remover the cylinder and the ring will be sitting where the port height needs to be. Take a sharp permanent marker and draw a line on the cylinder wall under the ring. Now you know where to grind to after you remove the ring.

For the intake port, you can rotate the crank to the desired timing then mark the piston skirt with a light scribe mark or a sharp marker. remove the cylinder and measure the distance from the bottom of the skirt to the mark you made and that is how much you need to remove from the floor of the intake port.

Best to do a lot of reading before possibly ruining an expensive cylinder. The guys that do it all the time make it look easy, but for everyone else it's real easy to make a mistake.

 

[camel2019]

I’m more or less wondering how guys come up with the numbers. like how do you know how to take x amount to make it open and close at x timing mark. how do you know that’s right for the given saw. I have ported heads for drag cars ect but 2 strokes seem like a whole different monster.

 

[camel2019]

What I’m looking at possibly porting is a pioneer 1100 holiday turd saw that I’m in the process of building out of 2 parts saws. And maybe a farmertec clone of a 660 at some point.

 

[Sepia]

I detailed above how to determine how much to remove to achieve specific timing numbers for the various ports. That is one method, and others will use their own methods and achieve the results they are striving for.

As for specific timing numbers; they vary from saw to saw, and by what the person doing the mods is attempting to achieve. A very general starting point for piston-port saws is 100/120/78 (exhaust/transfers/intake). That is not the Holy Grail and is only somewhere start for someone with no idea. After that, achieving the results you desire is simply trial and error. The experienced porters have a good idea what numbers work for popular saws when trying to achieve certain manners in a saw.

And on top of that are port shapes and directions and sizes. And then there are strato saws which introduce another set of ports to consider.