What I already know…
1. 400x has a proven motor. One of the lowest maintenance 400’s available.
2. 450r requires more attention in terms of internal engine components.
I have always done oil changes with no more than 20 hours on my oil on all my ATV’s. The way I see it is keep clean oil in the bikes is a cheap insurance policy.
So with good preventative maintenance. What is the life expectancy of the 450r motor when keeping clean oil in the motor and the valves adjusted?
My riding style is trail riding. No racing. Spirited riding from time to time. I buy a quad to keep it for a long time. I still have a 2003 400ex that I bought new in 2003. Still looking good and no issues. Just lots of oil changes and taking care of it.