I'm seeing the same thing Murnan is with this engine. I honestly dunno why they went away from the bore/stroke they had before, which was the same as the old Vspec and Speed. I would have kept with the old short stroke combination and changed some port timing and combustion chamber around... There is a TON of bottom end to be had with the older engine with a modification of course.

But now we work on what is out. Improving this engine isn't a problem but i don't feel like its the all around engine the old JX .21 was "same feelings twards the new speed and Vspec" as i like an engine that makes the bottom and will hold top end as long as possible while still managing to stay smooth and the old Vspec, Speed and JX .21 did this and REALLY shined once changed up a bit in my shop BUT in saying that everyone has their own preference on what they like. Myself i want it all.. top to bottom, smooth, run time, ease of tune with a great carb, longevity etc!