Question for the guys who are much smarter than i. I just recently got my cylinders back as well as new domes for my 4mil stock cylinder bike. This bike is a duner, not looking for a drag bike, just a good all around reliable dune bike. I do not know the port durations, but cylinders have "play port" set up for t5s and 34 pjs for 230 lb rider and 110 octane fuel. I do not know cranking compression as all parts are still in the boxes LOL, but my question comes as i was sent 19cc domes cut for 4mil stroke. I see it said on here quite a lot that you cant really rely on cranking compression for octane requirements, that UCCR is really a better factor to use. The cylinders are 65mm bore using 795 series pistons. If i have the correct info, the dome rise on that piston is .160" Now if im doing the math right assuming a .040" squish, the 19cc domes are going to put me at about 16.4:1 UCCR. Isnt this kind of high even for 110 octane on a duner bike. I was thinking i should have @ 21 cc domes. Again if my math is correct that would be closer to 14.3:1 Please discuss and thanks in advance for your help.