I got a old Barn Find 350 Big Bear, from my recently passed Father in law. This machine was used to drive cattle and haul minerals, as well as stringing Barbed wire.
I had to replace the oil Pump, as the grandkids pretty much wore it out. I replaced the Front cv joint boots which were tore, but just noticed the after market ones didn't last more than a year. I have found I can buy on Ebay, a set of complete front axles, cheaper than the boots alone. I have been using this ATV for 2 years now, but plan on doing a top overhaul this winter. So far it's been a tough machine, and worth the money I've have put into it. When you rebuild your Carb, make sure you clean the Idle Circuits with a very fine wire, and follow up with Carb cleaner spray, then blow everything out with compressed air. Check your float levels also. I use a Harbor Freight digital caliper, and used the pin that protrudes out the handle, when the correct measurement is set and locked. Hope this helps you. Hang in there the machine is worth the effort to keep it going.