Sold my 19/850 last year and bought 22/650/137. 850 had the rpm fade after a few miles unless the temp was -30c or colder, then it was 115 all day. I added big vents to the side panels. 5,00 miles and no other issues. Love the 650, easier driving in the tight bush, no trails. Guys I ride with all have 800’s. We all burn about the same amount of fuel. Uses way less oil than the 850, a little disconcerting. But there is no way the 650 runs with an 850 from dead stop to full throttle. Not even close.650’s I have ridden are not as responsive as 850’s. That being said, 650 will stay with 850 for a bit but it is only due to available traction. If all is equal the 850 smokes the 650 as it should. I am not putting them down as they are a great power plant but I will not be going down to one to get 1/2 to a gallon better mileage per tank. Besides if I rode with the 850’s I’m sure it would get same mileage trying to keep up.