RE: OS 1.20 FS Poor Performance
If your O.S. FS-120 is the old version with the two rocker covers, then the RPM level you're getting is about right. If you have an FS-120 Surpass, then it may be low on RPM. However, we've usually used a 15 x 8 APC propeller on our test stand, and see a little over 9,000 RPM. If the engine is really "right", and we have a good prop, we've seen the high 9,000's.