Cheap Gokarts for two kids?

I see various chinese manufactured gokarts for kids and was wondering if any of them are "decent" not decent as in good quality but that you will at least get some use out of them if you are mildly mechanical. My daughters are 4 and 8 and love to drive around their little power wheels jeep. I think they could handle something a little faster and well, I would like to have longer life per battery/fuel tank

If we had the property and funds I would get the kids a small side by side

Anyone have experience with these?

Have you looked into some of the Power Wheel modifications?  Might be an option since you already have some rides they like to play with.

I have a little bit, I saw people putting an 18v drill into them, definitely would be cheaper than a go kart

sounds like the "trailmaster" karts are decent and have a decent warranty kids could use it a lot longer than they will the powerwheels, mixed bag all over for quality it seems.

https://www.youtube.com/watch?v=9f-9jrLBfVk

Well this makes this look pretty easy :P

I bought my kids a Northern Tool kit for around $400. Add a Harbor Freight engine and we were in business for pretty cheap. It still works, but the kids have kind of out grown it. The grandkids will be using it next. So far, there haven't been any major repairs needed. It is due for tires. 

This is from 8 years ago. 

Looks like fun!