Thanks Turbot,
I see it's a relationship between torque and RPM's so you sacrifice one for the other.
The NX76 is rated for 5hp at 23K rpm so you lose top end. The other engines mentioned have less hp output throughout but higher rpm's at top end.
About 2-3 hp at 32k rpm I think.
So you get higher rpms to get you going quicker to make up for lack of torque and higher rpm's in the end to get faster speed.
Do I have any idea of what I'm talking about?
Aaahhhhhhh!!![:@]