Mind of its own!

[Shredder]

My brother and I just bought a 212cc Predator engine for our old school Thunder Kart we are restoring.
WELL.
We got it pretty good to go, went for a test drive. Accelerated decently and it just would not stop picking up speed. It started hallin' *** without us doing so.
So we tweaked the idle screw, that wasn't the problem. The gas pedal does have a return spring so that's good. But holy crap, it took off so **** fast!
Eventually this go kart will be my younger brothers, this problem seems pretty dangerous, obviously. Haha
I have run out of idea's for the problem. ANY idea's are appreciated!

 

[2SlickNick]

Is the return spring connect at the carb?

 

[Shredder]

Yes. I believe so.

 

[Poboy kartman]

 

[BirdFanatic]

I would think the butterfly is stuck or the throttle linkage at the carb is messed up

 

[Poboy kartman]

Well.....a picture is worth a thousand words.....BUT....if you disconnect the throttle cable....and it still does it....then it's the return spring or the above mentioned sticking butterfly...

If it doesn't it's possibly a kinked cable....

EDIT: Or you just have your cable adjusted incorrectly....

 

[landuse]

Put the kart up on stands, and push the throttle. Have someone at the back look what is happening to the linkages at the engine. Do they return when the peddle isn't pressed?