650sx revving up ?

[Naples]

I got a 650sx from a guy who said it had no spark. I cut back the plug wires and got spark so i figured Id try running the thing. Once it fired up it was revved up all the way even though the throttle hadn't moved. I kept hitting the stop button, nothing. Finally pulled the plug caps off. Probably ed up the engine.
Whats the deal? Why would it do this?

 

[Crab]

Air leak, you kill it with full throttle.

 

[Captain PegLeg]

Yep... the only way to shut it off when it does that is to pull the throttle wide open.

 

[Naples]

Where would it be leaking from?

 

[Crab]

Where would it be leaking from?

Intake manifold, worn throttle shaft, front or rear seals.

 

[Cliff]

my air leaks on a 650 was always the intake manifold

 

[Naples]

my air leaks on a 650 was always the intake manifold

Ill check that first.