A reply
Hi,
I have the same saw and have an import cylinder that I to would like to cut into, but have not yet. The saw is still stock with just a muffler mod and I can't imagine what a stronger saw would be. Anyways, I am novice at porting and have just completed my first porting of an echo 4600 (46cc) saw and it was a success. I, like you have a decent grasp on the basics, but am still daunted by the timing wheel, so bieng impatient, I purchased a scored echo 4600 and thought that the loss of it would be worth the money if I messed it up. I have never owned and echo and was very impressed with the quality of materials and design with the. I used and echo because they are cheep used, they have a longer strokes than norm, don't rev as high but have good torque, and the structure of the saw is pro quality and worth owning. This is what I did: I first honed the cylinder and cleaned it up with acid to the best I could, then with 400 grit sand paper cleaned the piston up. I cleaned up the piston grooves so the rings did not bind. I removed the rings and with the 400 grit and some oil, polished the surface by rotating it on the paper. My goal was to not spend any more money. With the cylinder, I widened the intake an exhauset by 3mm total or 63% of cylinder diameter. I then raised the exhaust by 2mm and lowered the intake by 2 mm, these were general numbers and protocol that I gleaned form this site and a perfomance tuning boot. I safe start to a modification. I then beveled the port openings a little and polished them both decently. I also opened up the exhaust on the muffler side some, by taking 1mm out on all sides, this leaves plenty for the gasket to seal and for structure. With the muffler I matched the gasket and the port then drilled the baffle and opened up the exhaust by the deflector to 80%. I put it all back together and it ran first pull, then I retuned the carb for the mods. I then when out and ran it with and 18" bar to fell, limb buck up 3 hard woods all around 12-8". My hope was to match the husky 346 with speed and power. I grew in speed and power as I put a couple of tanks of gas threw it. I hand great power and improved rpm. It now really zips threw wood and is a fast cutting and limbing saw for its size. I like it so much that I am going to put new rings in it and have picked up a couple more scored echos to play with. As a reference to what I am used to running and have worked on, 242xp, 272xp, ms440, ms066, cs2152, ms024, ms038, 262xp, 257xp. I hope this helps.
Would like some help on how far to go and an idea on what to do to the porting and what to set the squish to on my big bore ms660