So last week I took the 850 to the shop because of a hard start problem and a major lack of power. It was diagnosed as engine worn. Only 110 lbs and 150 lbs of compression. This will be the second engine problem on this 2012 quad. The oil and filter has been changed every 50 to 60 hours with a new air filter and sock each time. After this I don't have a lot of faith in the Mexican built North Star engine. The first engine made it 800 miles when a rock dislodged the oil filter resulting in a total engine failure, block and all. That was not a polaris quality problem. The current engine now has right at 5500 miles and about 300 hours. I think this is poor quality.