I put 120 hrs on the Predator 670, still runs great and decided to bring it in after 13months since I bought the extended warranty. No problem at all with the exchange, and took the option to warranty this engine for 1 yr for $150. They reminded me that this actually means bring it back in 15 months including the free 90 day warranty already on the engine.
The new engine seems to run a fair amount better, will idle at 850 and I must have changed belt tightness, engine position a little and it now hits 46gps at 4750 rpms. I definitely gained a few mph. I replaced the spring that connects throttle linkage with a solid nicely bent piece of coat hanger. It has a little slack in it and allows for a fast and slow idle. Solved the muffler issue as well, found an after market quad muffler on zon and welded it to the header, then supported it with a muffler hanger to the axle. Works great. Pics to come, I am at cottage away from the cart till Tuesday night.
Have had a lot of fun with this cart, it gets run a lot. Will be welding the crack in engine cradle when home. I plan on disconnecting the 12 volt battery before welding.