2 Strokes Down Under

I pulled apart an engine looking for bits for Link and found these.





The grooves on the pistons are the first I've seen. I don't know who or I don't know why. Probably to hold oil and reduce seizures. I've seen pin holes in various places on the skirt for this reason, I'm not certain or convinced of their need or success. I would rather better porting and reasonable tuning (rather than last poofteenth 'on the limit' optimistic tuning).

Anyone know of them or heard of the practice? I would be very suss about weakening of the piston!!!

Agreed it's probably for oil retention. But a good bore will have crosshatch for that anyway.
Looks to me like there is evidence of minor seizure even with their fancy grooves.

Nothing is going to stop a seizure if it's too lean or runs out of oil anyway.

Found this:
http://www.raysplace.com/pistonm.html

Looks like knurling was generally done to make the piston slightly larger in a sloppy bore, and had the benefit of holding oil.

Your one is not knurled though... definitely machined that way.