agco allis 5680

Hello, I recently bought a consigned 5680. the tractor just has 1400 hrs and looks very well taken care of however I have a couple of questions. The throttle sticks and I have to lift up on the foot to get it to throttle down the linkages seem loose but I just haven't been able to get it...

Although my father has been considering a new NH TN75 he came across an Agco Allis 5680 with around 2000 hours that he thought was a good deal. Does anyone know much about these air-cooled tractors or have any opinions on them?