Older diesels will "slobber" when they are cold. Slobbering is passing unburnt fuel out the exhaust in a black slimy mess. Get out and really WORK that tractor for an hour then after an hour of hard work, idle down and throttle up. See if it is better or not.
You may also want to add some fuel additive with "cetane improver". Add enough for 6 points. Higher cetane fuel burns easier. That may help a bit too.
jb
You may also want to add some fuel additive with "cetane improver". Add enough for 6 points. Higher cetane fuel burns easier. That may help a bit too.
jb