I have a 2012 prowler hdx 700 that has already been rebuilt once. I'm looking for the cheapest alternative! I had the boot in between the efi and the head tear and caused the engine to suck up dust. It hasn't even been a year since the last rebuild.
I've found several decent looking cylinders on ebay that were usable, cylinder plus new piston and rings will run 300-400 dollars after having the cylinder finish honed. I did a big bore kit on mine for around 700.00 dollars, this was done by CE Enterprises. If you decide to go that route there are other kits available, but I liked CE's deck modification as I've heard others have had head gasket issues. If serious about a big bore look at CE's web site. I've attached pictures of the top of the cylinder, and you will notice a big difference over stock! It provides much greater gasket surface! I love my big bore kit, it really woke mine up. I also added a Web Cam, Speedwerx Valve springs, a digital fuel controller, and a looney Tunes Exhaust.
New engine has its benefits! You get everything with it (not sure about the FI), warranty, and engine parts sell pretty quick if you decide to part the old one out, or keep it for parts. It would be a difficult decision for me, but I think most would opt for new.