There's such a thing as too much power!
There's such a thing as too much power!
Just for history's sake, I'll mention that the Rotax engine was in the Bombadier snowmobile. I think Polaris used it in the late 70s. And the old Cuyuna engine was also a snowmobile engine. Both engines ended up in ultralight aircraft in the early 80s because of a high horsepower-to-weight ratio.
From the safety viewpoint, I want to mention that there such a thing as too much power! When a gyroplane is designed, the designer selects materials and the cross-sections of airframe components based on projected airspeeds and loading. A gyro designed to fly 60 mph with a 45 hp engine becomes a new, untested projectile when more power is added!
Put it another way. If your gyro airframe is designed to fly 60 mph and you pack on enough power to fly it at 80 mph, what happens? First off, you're flying much faster than it was designed to fly. Something could break more easily because you're putting more stress on it. Second, your ability to maneuver may be compromised. Maneuvers you could do at 60 mph could break the airframe at 80 mph. The sensitivity of your controls is also likely to increase, making higher-G maneuvers more likely.
There's a tendency right now for larger horsepower engines to be used on two-place gyros. Unless you're a gyro designer with engineering experience, please, please, please contact the designer of your gyro before you put an engine of larger horsepower or greater thrust on it! This is especially true if you're planning to put it on a single-place gyro.
Moral of the story: Contact the gyro designer before adding horsepower, so they can be the test pilots instead of you!