This makes me nuts,
Yesterday ן adjusted the valves exactly by the book,
I adjusted the intake to 0.13
And the exhaust to 0.20

Everything went great, when I start the engine, it sounds great, no rattling, excellent sound, for 5-10 minutes until the engine warms up, then it starts rattling again,

What do you think is the reason? When the engine is cold it sounds great for a few minutes and then starts rattling

Do I needed to adjust the valves to a little less clearance?