Kingtight,

The only bad thing you can say about them is their price in the USA. They can be bought for a lot less elsewhere.

I have the .49. With the tuned muffler it gets 14,600 RPM on an MA 11x6 and idles at 1,850 RPM. All on cheap 5% fuel.

With its Czech ABC construction, and precision Swiss bearings, it will last over 200 hours.

It is the AK-47 of engines.

The bigger 10-15cc engines are timed and piped for low noise, low RPM operations. So they will spin a very big prop fast, but other high RPM engines, like Rossi and YS, will outrev them with "normal" .60-.90 sized props.

Sincerely,