Question about motor

My 426 is done after installing new upper and lower ends, how should I break it in? I was going to just ride it light one ride, but where my cylinder was replated they said to move the main jet up 4 sizes before starting? What works best?

Leave the main jet alone.

Start it, be sure oil circulates, and that everything looks good, ride it easy for 5 minutes and shut it down. Let it cool for a few minutes while you look it over, fhen start it and run it for about an hour at about 80% of its capacity. DON'T baby it, but don't thrash it, either. At the end of the hour, change the oil and call the matter over with.

Main jet thing sounds like it comes from a 2 stroke person, I can't see any benefit it would/could give you on a 4 stroke.

My break in is ride less than half throttle for 15-20 mins, then let it cool. Then ride it like normal, change oil after first hour.

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