Hi, sharing my story about noisy CCT on my Katana MY 2021:
After the annual service, i got a bad noise on cold start. First i was thinking about vibration with the cooling radiators protection i installed previously.... after 10 min / warm engine no noise anymore...
Two weeks ago, bike on the park place i try to find out the location / cause, for sure in CCT area.
Doing the service only engine oil and oil filter were changed, on the forum i noticed that an another mate got the trouble also after the service!
I started to investigate the specification of the engine oil >> in line with Suzuki recommendation for 10W40.
I compare with OEM engine oil advise and discover some differences especialy concerrning the "kinematic viscosity" @ 40°C.
My Dealer engine oil has 93,8 mm²/sec versus >20.5 mm²/sec for ECSTAR R9000, the melting point confirm also the differences >> -36°C for dealer engine oil versus -45°C for ECSTAR R9000.
I decided to change the oil, draining the tank and oil filter checking if metallic or plastic particles due to the bad noise and potential frictions >> luckely nothing to notice!
I installed a new oil filter and fill with this new engine oil >> immediatly with the first cold start to noise anymore !! i checked the level adding some extra cc. The day after again cold start and no noise !
In the meantime my dealer investigated with Suzuki, no know problems from their side with such engine, they offered me to leave the Katana for a check and when necessary to proceed to component replacement, but no more necessary at this stage.
Conclusion: i think the 10W40 oils are slightly different in specs/viscosities, from now i will continue using the ECSTAR R9000 for the time i am not getting any problem

Specs for comparisons available in MSDS / Safety Data Sheets
Regards from France !
Pierre