They are very good machines
I am a local shop owner for all types of vehicles and do alot of work for various fleets and car lots. Recently a car lot that sends me their vehicles bought a bunch of mountaineer atv's and go carts. I was thinking these are cheap pieces of crap until I worked on some and finally bought a pair of 300cc 4x4. I love them, they are not speed demons but they are solid and you are right they are yamaha based motors built in conjuntion with lanhai for yamaha for their outdoor powersports devision. I have had no problems getting parts and for the money you can have two for the price of one of the big four. The only thing to note with these atv's and go carts is to go over them and do some quality checks and inspections to make sure everything is tight. The go carts have given us some trouble. Mainly with some plastic fenders and their brackets ( just beefed up the weld for the bracket and made sure the bolts were all thight) these are made by cheaper labor and well for the price they sell for and the fact that I like to tinker and know what I own, I had no problem. We took our atv's to colorado recently and had no trouble with altitude and they were awsome. They are going to be offering a longer warranty as they role out more dealers. These things are solid and I have also recently riden a scooter and wasn't completely satisfied with it but yet it is only a scooter and it ran better than a moped. If you need more info let me know...