
To best answer your "how much" question, we would need to know where abouts you live. It comes down to supply/demand and personal opinion. Me, I would offer $150.....

If its a desired kart, I would not mention that.... If they mention it, then explain that in order for it to be worth a mint, it will need lots of work (that's read $$$$) to get it back to its former glory days.

spout off prices of stuff that needs to be replaced. When heard out loud, most sellers tend to understand and will open the floor to negotiations.....

You can even tell them you're really not interested in the engine, it's not period correct.... LoL What ever you gotta tell em to drive the price down. Walk away, tell them you will think about it and call them. Pull all the tricks out the bag.....
If there are a lot of used karts for sale in your area, these tactics work. If there is no abundance of used karts, well, it's kind of a sellers market........
