How many kms or miles on it? 

850 expires on 21st.  

I wouldn't worry about it on 650. They are very reliable motors. 850 you might want to think about it. If you can extend it for a reasonable cost before factory runs out, might be worth it. Sounds like you got a great deal on both so you are already ahead of game anyways. I been running VES gold and 91 fuel in my 650. With selector on 87, chance of engine issues is very low. Enjoy   

Im not sure about the Polaris’s but normally when a 850 doo goes down 5k won’t take care of it. I would think if you were easy on the machine it would make it to 10000 kms but I wouldn’t bet on it.

Think I will take.my chances. If it is not defective it should last seeing I barely get any miles. Thanks for the input.