Hi Dave,
Great to hear that the engine performs well for you. What airplane are you flying it in? I don't see any problems in airplanes designed before 1983, but some of the later .60 sized 'turnaround' designs might pose a bit of a problem. The tank location is unsuitable for unpumped/pressurized engines (inverted engine set-up such as the Aurora, Dash-5, LA-1, etc.). The 10mm Carb (.394) is a pretty big opening; larger than the old Perry pump carb (.375), but still not the huge (.425) throat of the YS .60FR. Back in 1980, after I acquired my first YS and was also running the OS .61V, I experimented with running the VF with the 7D carb with the brass insert removed. I got more ground rpm, but reliablility was poor as the needle setting needed to be quite rich to keep the engine from going lean in long verticals. A Perry pump helped, but the YS still had more power. My bench mark is to be able to pull vertical, fly a 4 point roll and pull out without the engine sagging.
As we discovered in the mid '80s, the YS .60 was just as happy turning a 12 x 9 prop as an 11 x 7 and fuel economy was much better. The lower rpm being run with the larger props eliminated the need for large carb intakes which is why the Hanno and YS long strokes had smaller carb intakes.
I think the most impressive aspect of the new Nova Rossi's is the performance to cost ratio which seems pretty outstanding, plus they appear to be very well made (typical Rossi).
- Will