Hi EVERYBody, I have an ol 4520 jd that's about to make me pull all my hair out worrying with it.. what it is doing is when u first crank it up it smokes badly . Its a white diesel smelling type smoke and it mis a lil. So I thought ,Ok no problem probly injecter bad replaced all 6. Ok tried it again same thing no change. Ok no problem pump had it rebuilt by highly referd company. Put pump back on same thing . But what does is when I pull a disk with it for a while it clears up and quit missing, runs good. But when I cut the tractor off a few mins it does the same thing again. It not using oil , not adding water , not running hot,it does have a lil blow by out the vent tube but not a bug killer. The ol gal is strong pulls good I tried talkn to jd tects and tried there advice but nthn works.. any info would be greatly helpful. Thanks