chadihman
Addicted to ArboristSite
I recently cut the squish band,lowered the deck and ported a MS361. This was the first saw jug I ever put on my lathe and the second saw I ever ported. I ran two tanks through the 361 yesterday and was really impressed with it's power. It was blowing a tad over 200 psi compression. I ran it some more today and then put it up against my brothers stock 361. Both have new chains on 20" bars and the ported 361 has an 8 pin sprocket. I got sick when the saw seemed to loose rpms and bog down. I gave it throttle and it cleared up so I figured it was ok and we started to video. My ported 361 beat my brothers stock 361 by 4 seconds but I felt that my newly ported 361 was not running as strong as the day before. I really felt sick when I could feel the pull cord pulling much easier.
I got the ported 361 home and tested the compression. It was now blowing 140 psi:bang:. I pulled the muffler and found a slightly scorn piston and rings that were worn also:bang: I'll tear it down monday to see how bad it really is. The saw was tuned 13,500 yesterday and then I leaned it out to 14,300 today. I guess that was where I goofed but I sure thought it was still four strokin. The rings look as if they were snagging. I think I may have made the top of the exhaust port a little to flat.
I'm planning on starting over again and thought I would try a big bore kit and port it to the same numbers. Or find a good used jug. I think this saw would have beat the stock 361 by more if we would have taken the video yesterday when it was blowin over 200 psi.
[video=youtube_share;Wc9fO3H8fhk]http://youtu.be/Wc9fO3H8fhk[/video]
I got the ported 361 home and tested the compression. It was now blowing 140 psi:bang:. I pulled the muffler and found a slightly scorn piston and rings that were worn also:bang: I'll tear it down monday to see how bad it really is. The saw was tuned 13,500 yesterday and then I leaned it out to 14,300 today. I guess that was where I goofed but I sure thought it was still four strokin. The rings look as if they were snagging. I think I may have made the top of the exhaust port a little to flat.
I'm planning on starting over again and thought I would try a big bore kit and port it to the same numbers. Or find a good used jug. I think this saw would have beat the stock 361 by more if we would have taken the video yesterday when it was blowin over 200 psi.
[video=youtube_share;Wc9fO3H8fhk]http://youtu.be/Wc9fO3H8fhk[/video]