6.5 Tecumseh Go-Kart

it sounds to me like maybe the kill switch is shorting out? its hard to tell what it is without hearing or seeing it. but also, maybe the float is sticking somewhat in the bowl of the carb?

When she hits a rut, the spark plug lead could shake loose, and then reconnect internally.
But, the black smoke suggests that it is running very rich for a second and the float is getting jammed down. Strip the carb, clean it and reassemble. Should solve it

I think I may have purchased the same go cart! I also had the same problem. I think I have found the problem? I had changed the oil for the first time and noticed the same issue, The engine seems to foul over rough terrain,right? I had over filled my oil (probably causing blow by into the top end) and the result was an oil stain on the air filter. I changed the oil again and made sure not to over fill but it was still farting out over just about any bump. I then replaced the air filter (due to the yellowish circular stain on the paper filter feeling it was reducing air flow) and every so often I have to replace it but that worked. My cart was the yellow cart with full suspension and the 6.5 hp tecumseh power sport engine. if you need more tips let me know!

This is a pretty old post, but yeah, if you overfill with oil, some engines can't take the extra oil, or the rough ride, and spew it through the breather, into the air filter, unless its a oiled foam, and is a paper filter, it'll clog it, resisting air flow.