I am mechanically inclined, but working outside of my realm. My nephew has 2011 Honda CRF150R dirt bike. He decided to do his own own change. He seemingly drained the engine oil, then filled the transmission oil. He proceeded to ride, it quickly locked up.it would not kick over, then eventually did, bit no fire.

I have taken it apart, expecting the worst. Right away I found a broken piece of cast, sitting atop the head, below the camshaft. I found the casting in the cam holder was broken. I took the head off and it looks ok, no cobtact or issues. The cylinder wall still had slight oil, and piston looks ok. I did not remove the cylinder as I do not see a need to as of yet.

The camshaft looks as it got hot, but lobes look OK in my opinion. Should I just change the cam holder? I have attached a video I found where the gentleman had the same concern, and exact same piece missing/broken. He changed the cam and mentioned it is not at the correct location when set at top dead center. This makes no sense to me as the cam is directly bolted to the gear.

Similar video: https://youtu.be/Qn4k4yuSk9I

Your opinion and help appreciated. Trying to fix on the cheap,

Is the cam ok o re-use?

Broken piece on bottom of camshaft holder, bucket seems ok

Where the broken piece was sitting
as a favor!