if the DE is rated at 140 at 6400 rpm, does that mean the engine is peaking there? or does the hp peak further as it reaches 7500 rpm?

doomland

Yeah that's what it means. On a HP graph, the HP peaks at 6400 (?!! I thought it was 6800rpm). From there, HP starts to fall off, but that doesn't mean you completely lose power. There's just no real point to revving far past the HP max.