I'm thinkin that's gonna tap the sparkplug.I don’t see any reason why the specs mike wrote on the first page wouldn’t work with the hyway pop up. You would end up with a pop up on a pop up. No clue if there’s enough room for that in the cylinder
I'm thinkin that's gonna tap the sparkplug.I don’t see any reason why the specs mike wrote on the first page wouldn’t work with the hyway pop up. You would end up with a pop up on a pop up. No clue if there’s enough room for that in the cylinder
I think that's pretty much what trappermike recommends in his initial posts.So I tore the saw back down and lowered the squish from .025 to .018, squared up the intake and widened it just a tad. Compression went from 150psi to 162psi. It free revs to 15k now. That's a 500 rpm increase after lowering the jug. Before I was having some idling issues where it would load up and then almost fall flat. I'm not sure if it was the carb or not but after opening the intake the saw idles and runs great now.
If I build another one like this im not going to raise the exhaust at all and see where that puts compression and max RPM.
With the mod I do compression with a stock ex. port is around 200 psi(Far too much for my liking),with the ex. port raised 2mm the comp. is about 170,which is perfect for good midrange power and top end power from a 72cc saw with more ex. duration.
I’m not sure about the hyway piston. This thread is just about the normal 268 piston. I did bring it up earlier because I was curious but mike said even with the regular 268 piston you’ll get about 200psi but he likes to raise the exhaust to the point compression comes down to 180. With the hyway you would get a mega pop up
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