Grizzly 450

I start the Yamaha Grizzly 07 and it works normally for about 10 seconds then the RPM start to go up and alone. Weird I know ... ideas?

This could be a vacuum leak between the carburetor and the head if carbureted. Squirt some WD40 in the rubber connector and see if the speed changes. If yes, you have a leak.

If fuel injected, it could be the throttle position sensor.

Yes, deff fault vacume ...