Downunder,

The manufacturer's data sheet states the practical RPMs for this engine as 2000 to 16000 RPM. That is practical, so I assume it can go higher. I had the engine leaned out alittle too much by ear, and I attained those RPMs verified by a cheap hobby shop tach my brother loaned me and by a more sophisticated tach used by the machinists that is used to double check the shaft RPMs of the pump they are working on. The 20k (or 40/2) figure was entered into the meter as a high point because the machine needs to know what parameters it is working with. To be honest, the engine was absolutley screaming on that run and this was the only time I had it rev'ed that high. It was a bit scary... It was running very lean at the time, so I don't think it was four-stroking.

I am also starting to believe that is was a poor test-stand design, because as I said earlier, the vibration seems much more normal when the engine runs on the plane and my experiance with these things is limited to 25 years ago, as I am just starting this obsession again adn wanted the benefit of you guys who know alot more about it than I do.

I think the stand did not allow the engine any dampening and niether did it hold the engine solidly enough. The only reason I posted the graph was because the large spike seemed so out of proportion to the rest and the machinist that ran the tests seemed very apprehensive about the spiking. He indicated that if a pump showed that much linear movement, it would be brought off-line immediately and overhauled. That sort of worried me a bit...

I greatly appreciate everyone who posted to this thread. You've given me some extra knowledge and made me feel better about the thing. Now... To crash, er I mean fly it!