I don't think a simple valve adjustment caused the sudden noise.
1. Can you isolate where the noise is coming from? Top of engine on the left side or at the crankcase on the left where the starter gear train is situated?
2. If the noise is coming from the top end and there is no real miss you'll have to check the valve train. Maybe something broke like a banjo bolt or cam retainer that is rattling around inside. Maybe a valve shim was spit out of it's holder. I wouldn't drive until it is checked.
3. Does the bike still run smooth with no miss? If so, then it probably isn't a vacuum leak and you haven't dropped a valve.
4. If the bike runs rough/misses, then check everything mentioned. Vacuum caps on the carbs and AI system. Dropped a valve? Broken cam etc etc.
Look for the simple things first though.
