ORIGINAL: MarkNovack
Final prop selction depends a little on flying application and nitro. With Coolpower 30%, 16-8 puts the RPMs in the 9200-9400 range, perfect for the motor. For 20% nitro, smaller props (15-8,16-6,7 will work well). Look for keeping it in the 9200-9600 range. On 30%, we were turning 10,300 on the 15-8.
For pattern, a 15-10 is awesome. I agree with the break-in prop as a 15-8. Also, put this one on the bench for a few tanks full. I recommend a gallon on the bench. Many people running this motor are experiencing deadsticks due to overheating. Once the piston and ring seat in nicely, the motor will reach complete reliability and maintain nice even temperatures.
Mark
Maybe it is not very approprite to compare but a Zenoah G26 can turn a 16x8 at about 9000. If YS 100 can turn this 9200-9400 then it has to be really awesome.
Generally OS and other 140 size 2 cycle manufacturers ( Webra ) advertise their two strokes by saying these do not have the complexity and maintenance of 4 strokers. I would like to ask YS users that is there something has to be done extra to maintain YS engines? The most compex thing I do with my 4 strokes are adjusting the valves in every 50 - 100 flights, MAYBE a bearing change every year. Isn't it the same with YS ?