i noticed that my engine was smoother between 4-5000rpm, before i did an oil change.
previous had 10w40 in it and now i went for motorex 15w50.
now the bikes pretty vibey that it bothers me...
can an oil change to a different viscosity cause this?
i also suspect some oil consumption with the 15w50, didn't notice this with the 10w40, but didn't do many miles with the 10w40.
i bought the bike like this and changed oil after about 1500km.

valves make no sound, idles well without any extra noises. runs smooth upto 3-3500rpm

bike has a pipercross filter, decat original exhaust, fuel mod, fresh spark plug.
(come to think f it, i did change to CR7EIX, coming from original spark plug)

can't really say when exactly it changed...

any suggestions bases on real life experiances.
i did come up with the idea myself to change il back to 10w40, thank you

ciao, Hannes.