'67 Farmall 140 Problem

I recently converted my dad's 140 from 6 volt positive ground to 12 volt negative ground. It's been stored(inside) for about 2-3 years without being used. I replaced the alt..removed the voltage reg....replaced the ig coil with a 12 volt coil with a internal bal resis. Replaced the points and conden...fresh gas/oil. When I hit the starter..it fired up and ran(good) with full trottle only. No matter what i do...it runs with full trottle only. Checked all linkage/levers...they appear to be working fine. Pulled the gov housing off..nothing appears broken. Does anyone have any suggestions? Thanks!