140 to 150 psi on most 2 cyl Rotaxs. They tend to be a higher compression , higher torque, lower rpm running than most of the compitition. In years gone by. The other brands would rev higher but less compression. That has since changed. As long as both cyl are within 10% of one another you're good. But Rocketman 122 is borderline. Wouldn't hurt to put a set of rings in there.