Rebored? I did not think any modern saws use iron liners.
Question on Stihl 025 Tuning
- Thread starter 2lumbarleft
- Start date
Help Support Arborist Forum:
What ever that piston is, I would like to put one in my ms250. It needs compression. Can you figure it out? Pictures? Measurements? Anything.
2lumbarleft
ArboristSite Operative
Thanks to all that contributed advice. I went through my parts box and found a brand new Chinese Farm-Tec carburetor for an 025. I removed the original equipment Stihl carburetor that appears to have been rebuilt by the seller of this saw and installed the Chinese cheap-O as an experiment. Saw started right up upon completion and adjusted out just fine. It idles well, accelerates quickly and does well under load. The problem with the wet muffler has been cured. Compression remains sky high for an 025. I am wondering if the seller didn't install some aftermarket piston. It is clear he took the time to hone the cylinder. OH well, I will never know for sure. I'll just buy some extra starter rope to keep on hand, as this thing remains an absolute beast to turn over. I know that Stihl chainsaws have more pull resistance in this particular series, and I own two other MS-250 chainsaws. The highest compression that I ever recorded on any Stihl 025 or MS-250 was about 155 psi. I am getting 195 psi with the same gauge as used to test the others.
2lumbarleft
ArboristSite Operative
I am sorry, but I am not an experienced Stihl chainsaw rebuilder. To answer your question would require a complete autopsy, and I am not sure we could ever figure out the source of the piston, if it was indeed an aftermarket replacement. That would require someone with more experience than I possess.
You could try measuring the squish on this 025 and one of your MS250s to see how they compare It's possible to reduce the squish clearance and increase compression on a clamshell engine, just more work than with an engine that has a separate cylinder.
