The stock piston is domed in itself, but I like the looks of your dome. I usually don't modify the windows in the piston, they develop idle issues and lose bottom end with too much modification. Chippysatv will back me up on that one. My personal theory is that the case volume is borderline too small, as this is a big bore and stroker in those cases. I usually discard the bottom ring completely and grind that whole corner out of the port. My personal 026 is at 92/116/74, with .0165 squish. Upper transfers are untouched. Chamber was cut the old school sandpaper glued to the piston method to match the chamber to the existing dome. It's a 4 year old build at this point, and it is my go to saw. There's a bunch of video of it on my channel here and on my TikTok. I run 3/8 on it exclusively, normally a 16 due to how I usually use it, but it has no issues pulling a 25.
Yeah man I feel that with builds getting boring doing the same numbers, machining etc.. gotta try new things to keep it interesting. That se is gonna run good
Charles, I saw your video "2 Stroke Tips & Tricks Part 2" where I noticed the incorrect theory of "piston surface vs. bore" and your theory you are using also here. In general "Work done by gas" is W' = p1*V1 - p2*V2 resp. by Isobaric expansion W' = pk* deltaV. That's about change of volume not surface of piston. Larger surface of bottom of bottle also doesn't make higher volume of bottle. Domed piston has some benefits. Higher compression rate, fuel burning longer (longer distance) = less stress on bearings, less vibration of bottom of piston (mostly by larger diameters).
In that particular video @23:00, Mr. Charles explains the combustion chamber is matched to the domed piston which decreases volume of the combustion chamber which increases compression. Mr. Charles @24:00 goes on to say he does not claim to be right, but rather "his observations" which were to be dyno tested...
I would also add that in a flat top vs. domed piston scenario, the domed piston does in fact have more total surface area compared to a flat top. If the squish or ceiling height of both combustion chambers are the same, the dome configuration also has more volume at the same compression ratio. If we measure a partial sphere and a disc of the same diameter, the partial sphere "displaces" more area. This is all part of the R&D and combination of recipe's that are being tried and proven in the testing and competitions Mr. Charles is very active in.
