woods porting tips

[clayczech]

hey I just recently joined this forum and have been reading it intensely and find it very helpful. I have done a few saws but only stock. So my question is woods porting. how do you know how far to go with it? I mean the exhaust port, how much can you take out before it starts to hinder the performance of the saw? do you guys have a rule of thumb for it? same on the finger ports and intake. also side note, do you have to cut the muffler apart to get to the baffles on a Husqvarna 55? thanks in advance for all the help. I'm gonna be here a lot so I might get a little annoying in the future. lol

 

[ncfarmboy]

75% of piston diameter for in/ex port width (ex: 46mm piston x .75=34.5mm wide). Never done finger ports probably won't =don't know. 80% of ex port (length x width) muffler outlet. I believe you have to cut a 55 muffler.
Shep

 

[nmurph]

The general rule for a work saw is to make the port width 65% of the diameter of the piston. That is a chord measurement- measured straight across the port opening, not measured around the arc of the cylinder. You can go a little wider with more bevel or more arc in the port from center to edge. But you decrease flow when you do so. Stick with 65%, make the corners relatively square, and put a nice bevel on the cylinder wall/port transition.

 

[mdavlee]

If I'm going to be raising the exhaust a good bit I don't widen it at all. No real need in it. Finger ports help o some saws and some they don't. They sure do look cool and sound cool though

 

[clayczech]

on the exhaust port, do you do, what i like to call a "revese megaphone", where its wider at the outer side and narrower on the inside?

 

[ncfarmboy]

75% of piston diameter for in/ex port width (ex: 46mm piston x .75=34.5mm wide). Never done finger ports probably won't =don't know. 80% of ex port (length x width) muffler outlet. I believe you have to cut a 55 muffler.
Shep

Thanks nmurph for catching my error. I apologize for bad data 75% should have been 65%. Need to proof typing before posting.
Shep