Weird noise after top end

So i rebuilt my 09 yz250f (piston new valves) and i put it together and now it has this weird noise that makes me very uncomfortable when riding. Almost sounds like piston slap, here is a video of it im just lookin to get this thing fixed fast, been off bike 4 weeks and getting verrrry moody lately with no riding. th_F30CFC1C-6773-48BF-A9FC-22F840AF5600-

I sometimes struggle with diagnosing by video but to me it sounds more valvetrain than piston. I'd pull the valve cover and have a quick look at cam chain, valve clearances, make sure everything is getting oil, etc. Is it louder when it's cold? Piston should grow slightly and get a little quieter when it warms up. Clay

No it doesn't get louder or quieter then cold or warm it stays pretty constant. I took out my cams and put them back in and inspected everything up there and it all looked fine. It seems like its louder on the right side of the engine it may not be but seems to me it is

I compared it to a different Yamaha and it sounded the same... The new valves were steel and they used to be titanium could that explain why it sounds louder to me.

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