How do you figure out the best valve settings for a motorcycle?
Enjoy the bike and ride it now. If you touch it you'll be walking. You've got all these ideas and think you know better than the people who designed the bike. Recipe for disappointment! A 125cc motor and you think it's "crazy fast"? LOL
"I'm thinking of upgrading the fuses and relays, the starter motor"…"thinking about changing the engine bushes" For what reason? How?
Read the service manual
Sounds like you have a lot more ideas than knowledge. If it is new , have it fixed under warranty. If it is not on warranty, leave it alone. The stuff that you are talking about will cost you a lot of money for a basket full of parts and a bike that does not run
Simple rule of thumb- The valve guides should be half the spark plugs setting. Leave the sh!t you don't know about ALONE.
Leave your bike alone. Learn how to FIX it first because it will break SOON and there are NO parts or dealer support for it.
It is not a thing you can figure out. Get a service manual and adjust according to that. If the adjustments are correct leave the darned thing alone. The things you're talking about are crazy. You do not need to do them and more likely will ruin the machine with your tinkering.Go back to the shop where you bought it and ask them to check it out, if it's idling too fast or acts like it's out of balance. Your options on the starter may only be the one that's on it.
Your bikes biggest downfall is the idiot owner. Upgrading the fuses? wtf? Do you think bigger fuses will make it go faster? Leave the engine alone
Get a recent-model wrecked bike, take the engine out and tear it apart. Buy a book on motorcycle repair. Buy a mechanical engineering textbook on internal combustion engine design. Read up on materials science, expansion coefficients, the properties of metal types, grades and alloys and all like that. You do realize that replacing bushings can require that they be dunked in LIQUID NITROGEN, right? Got some LN2? Gotta dewar? Gotta hydraulic press? Like wow, dude.
Save your money and buy a real motorcycle when you outgrow this one.
You go on line. Look it up. Then have a translator as it is in Chines. Or other Asian language for most. Best is to take it to a dealer or were you bought it. As they say here. China's selling point is there bikes are 90% as good as Jap bikes. But only cost 75% as much. As for what work can be done to them. Go to the cock fights or other events were there are lots of motorcycles. Find some like yours. Buy them a beer set under a shade tree & find out about all you need to know about yours. This may cost 2 or 3 beers Pints with ice at most. Works for me best in Asia.
Reading manual helps. 4 stroke engine with OHC? or OHV old pattern Honda Clone? intake at .004 inch, exhuast at .006 may get you started. some clatter is acceptable cold, light tick warm. Check lash at start, then adjust a little. common for break in miles to get some extra slack- need to adjust to specs and then maybe 4000 after the first at 1000 miles. l
By pooping on it.