MT speed

[dc]

Is it the horse power that gives it speed(top end)
or the RPM and gearing

[Inferno Runner]

When you say "speed", do you mean acceleration or top end?

Generally, I think horse power relates more to the acceleration side and more RPMs relates to the top end speed side. Porting, pipe and gearing are factors too. Regardless of HP, you can gear for more torque and bottom end punch (and lose some top end); you can gear for more top end speed (and lose some low end); or, find a happy medium that suits your situation and terrain for the best overall performance.