What is a good engine break in oil?

I have a 2009 yz450f and I was curious to see what a good break in oil for it would be. Currently im running motul 300v 10w40 full synthetic ester based oil in it and I was told high quality oils such as that are not good for engine break ins. Does anybody have a good oil suggestion for me?

Non synthetics usually the best for ring seating.

Non synthetics usually the best for ring seating.

X2! Assemble the engine dry, and use non synthetic.

this sounds awesome but how can i be so sure that blasting my engine on a brand new piston is the correct thing to do. It sounds correct in the ways the article explains it but i think I need some more proof than this article provides, (actual tests, pictures, diagrams, etc). Have you ever used this method?

wait never mind this article does show pictures and stuff, I spoke to soon.

wait never mind this article does show pictures and stuff, I spoke to soon.

Have you ever used this method?

I drained whatever oil was in the bike. I used the section minus checking the water temp using regular oil before switching to Rotella.

On the Racetrack:

Warm the engine up completely:

Do one easy lap to warm up your tires. Pit, turn off the bike & check for leaks or any safety problems. Take a normal 15 minute practice session.

and check the water temperature occasionally. The racetrack is the perfect environment to break in an engine !! The combination of acceleration and deceleration is just the ticket for sealing the rings. Go For It !!

Mind you, I'm by no means fast, my 4 gear KX hardly ever sees 4th gear so the thing never hit any rev limiter.

The idea that synthetic oils can't be used for break in is one of the most enduring myths in the automotive world. It's complete BS.

I use whatever oil I regularly use in the engine to break it in, and over my career, that would be hundreds of them. Not one has ever failed to seat the rings in a top end that I prepped and assembled myself. Also note that several top of the line performance vehicles from major manufacturers have their brand new engines filled with full synthetics from day 1, and many of them will void the engine warranty if anything other than a full synthetic is used.

It is the prep and assembly of the build, and the break in method that determine success or failure, not whether you use a synthetic or not.

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