High pitched noise

Hi
After the second tank of 90 oct + semi sinthetic oil I prepared a 98 oct + semi sinthetic oil mix
98 oct pump gas in my country has a strange smell, not exactly good old gasoline
Used it today going to work, and coming home the engine started a high piched noise, like something out of oil (or am I just paranoid?)
Barely audible with the engine running
Engine on and clutch pulled there is noise
Engine off and clutch pulled there is no noise
I asume it comes from the engine
Is it normal?
Is my engine dead? (hope not)
Thanks in advance

Sometimes the clutch gear will rub on the case on the right hand side. Pull the cover off and look for metal shavings and put a dab of grease on the gear if it is dry. I also put grease in the hole that hold the clutch cable under the carb. Unscrew the fitting and put some grease in there, I used a neddle to get it in cause it is tight....Also really no need for high octane gas since these are low compression engines.