So, I just started using my Tecumseh H70 *I think its year is around the 70s - 80s, I honestly have no idea or knowledge on this engine that's just my guess. But I've been rototilling with it and it has been dying when it would touch the ground and didn't even rototill, I've adjusted the mixture screw a lot and I have it one turn out and a small touch past that after the one turn out, but then when I put it high throttle it will sputter and die when it touches the ground and black smoke comes out of the muffler, there's also white smoke coming out of the oil drainer tube at the bottom of the engine (I think it's smoke at least), I have w40 motorcycle oil in it and I just replaced the carb with a cheap one. I honestly have no idea what's wrong with it at this point, I know that the conditions are crappy for rototilling and I will probably get flak for rototilling in the mud... But that stuff is clay and I'm not sure if it will dig that clay up when its rock hard (Ps: that's not a garden, it's for planting boxes so grass won't grow up). Anyway, it will only rototill and dig deep on a certain spot on the throttle otherwise it sputters and dies. So yeah if anyone has any thoughts or suggestions I would be happy to hear them! Here's a video of what it's doing (Ps: the GoPro is in my mouth so there's breathing)
This video doesn't show it rototilling and dying that's when the black smoke comes out, it's really weird, this kind of does it as I'm looking back at the video I have posted, when it's rototilling it will start to power out and sputter and that's when the black smoke comes out, and then it runs rough until I throttle it down again and then sometimes it stays running or it will quit.