What oil for 400ex

I run amsoil 10w40 motorcycle oil. Make sure what ever you get its for wet clutch applications

No seperate trans oil
Oil filter is on right hand side(sitting on bike)
Round cover with 2 bolts closer to the front

I run tires at 10 psi front 7 rear for trail riding. But this is all about preference and what type of riding you do.
For mx i run 7 in front 5 in rear.

Good call! It sucks being dislexic lol

I run 10w40 all year round. Never had an oil related issue. That being said if i was riding in 100+ degree weather or riding sand dunes a.k.a. in an oven. I would probably up to 20w50.

I dont get along with that kind of heat well so i just dont ride when it gets that crazy hot out.