I don’t know where to start but I have a Kodiak Ultramatic Yamaha I don’t know if it’s a 4x4 or a 4x2 or if it’s a 400 or whatever but It won’t speed up it’s stuck only going 10mph If I try to push the throttle in it will start revving up and start moving slowly if I push it in all the way it doesn’t take off it like it’s stuttering to go to higher speed

 

Could be your reverse rev limiter coming in when it is going forwards, I think there will be an override button near the start button on the handlebars, try it and see if that stops it stuttering. Alternatively, carburettor could need cleaning out. Though just how hard are you revving it at 10mph? If you seem to be revving really hard and not going very fast, the clutch may be slipping, or the variator stuck.

You can tell if it is 2wd or 4wd by does it have a differential and drive shafts between the front wheels. 4wd Ultramatics also have a 2wd/4wd button above the throttle lever.