First time posting on here. Me & My Son recently acquired an '05 YZ450F with a seized engine. On further inspection, it turns out the crank has seized but the rest of the engine is perfect. My question is should we replace the top end as well as the crank? The Piston, Bore & Valves etc are in perfect condition, zero scoring. I'm happy to replace the Crank while my Son is insisting we do everything (I'm paying for it all btw). Thoughts?