Which Piston would you use? (Stihl 026 Pro)

[smokey7]

If time isnt a problem.... then the op could build it with the no-name piston. Then pull the topend and replace it if you felt like it. Then it could be measured to see how much it was worn. Im under the impression that the uber cheap pistons dont have the proper level of silicon content. Which im told causes quick wear and strength issues. Myself im curious how much wear happens and how quick

 

[davefr]

Guys,
I just completed a vacuum and pressure test.

Vacuum:
Started at 7 PSI
6 PSI after 30 seconds
5 PSI after 60 seconds
4 PSI after 120 seconds
3 PSI after 180 seconds
0 PSI after about 5 minutes

Pressure:
Started at 7 PSI
6 PSI after 20 seconds
5 PSI after 45 seconds
4 PSI after 60 seconds
3 PSI after 90 seconds
2 PSI after 165 seconds
0 PSI after about 5 minutes

I decided to dunk it in a tote of water and pressurize it to 10 PSI. There's only a tiny stream of bubbles coming from the decomp valve and absolutely noting from the flywheel or clutch seal area. I'm going to conclude the bottom end is just fine. Is a tiny leak from the decomp valve an issue? I assume it's not but might just block it off.

 

[cuinrearview]

How long do you think it will take for that "acceptable" leak to go to "unacceptable" to "damaging"?

 

[pioneerguy600]

Almost all used decomps leak. usually quite slowly and I remove them whenever I do a pressure or vac test. The OP`s readings are within reasonable limits. The 026`s really do not need a decomp, all of my own are plugged with an OEM fitting.