I'm very beginner. During my 1st two rides for learning, I couldn't apply the lesson that:
Release the throttle when up shifting.
I had this thing in my mind but at that time I could not apply the knowledge because a lot of things were going on in my mind. So I forgot to release throttle.
Note that I wasn't riding at high speeds. Also my bike is only 110 cc with 4 gears. I released the clutch very smoothly even when I didn't release throttle.
So the gear up shift process wasn't horrible, but at the same time it wasn't smooth either.
So I guess it was not smooth primarily because I didn't release throttle.
And I came to realize about this a few days ago only, while doing my next learning ride. I'm not sure it had done any damage to my engine or not so far but it runs smooth just like 1st day. I even changed oil for safety.
Now, even though I use correct method of gear up shift (i.e., releasing throttle), I still make the mistake sometimes.
So I'm just curious. I want my bike engine to stay good for maybe 5-7 years at least. Engine is most expensive part as far as I know. I guess clutch plates or gear "system" in bike isn't that expensive in entry level bikes. And they can always be replaced.
That's what I want to ask about: Does not releasing throttle while up shift wear the engine (reduce engine life) or does it only affect clutch and gear parts life?