law is not so straight forward, by right any non-standard modification is illegal, because we do not have the term 'street legal'.
ride with moderation, you shouldn't get into much trouble with the blues and whites. you should worry more of thieves.

Depends on luck, meter speed between 120 to 130 kmh is the average, not considering other factors. 140 is not unheard of.

Sometimes, for stock engine, the high end RPM is less power than advertised. In this case, using a bigger rear sprocket can actually allow the engine to compensate the lack of power, achieving higher RPM and bring the bike to better top speed.

Yes, bigger rear sprocket in some cases results to better top speed.

That's why, if using stock sprocket, and the final gear max RPM can only reach <8.5k, then you need to increase the rear sprocket.

Stock sprocket may be suitable, maybe not, depending on how it performs on the road.

For highway only, get a dunlop TT100, most durable so far I've seen, but make sure don't get old stock more than 3 years. Of course the corak bunga is not nice, but that's how a general purpose tyre suppose to look like.

Autoclutch jam, got EO?

EO = Engine oil.
Are you sure is gear jam? Or is block jam? Got coolant?

you know how to check coolant? Need to open radiator.

I treat you as noob, so I don't think it is problem with your gearbox. I think is no coolant. Please check.

My bad, to answer your question, I think it is the coolant in the radiator that is not enough, not the reserve tank.
The one behind the coverset is the reserve tank.
Reason I suspect that, is because the motor overheat and jammed due to no coolant in the radiator, and normally when this happens while you are riding, it will drag the bike and lock the gear along with it. Since you mention it is SS, and that when the engine stops, you think it is gear jammed...

To check it, open the radiator cover and look for coolant in there. Let us know.
If go kedai, means you might have to pay for it.

I never care until something goes wrong. Some people change every 10k km, some just follow service manual. Some people will flush radiator so they can change to other brand coolant. I recommend just opening the cap to check coolant level once a while, and make sure reserve is full.

That is to maximize head area... until they get some wetflow bench done, no 'racing' head is worth my money. :$$$:

mana gambar?

Another noob question. You got read manual or not one?
Every service interval change.

who ask you to service every 3000km, bro?
Service manual is every 6000km.
At 6000km - check, clean, re-gap. At 12000km, change plug.

Again, like EO, if jaga bike, paling-paling also 5000km service bike.
Copper plug can tahan, GP plug, sure makan already.

Perhaps deswai you change to victor... haha, you'll love the 4T in gearbox last you long long. Just worry 2T only.

for plug change, 10k km about right. Otherwise will reduce power and fuel efficiency.

Copper original is most durable, because it is physically bigger.
Iridium is only on the tip, when it is gone, bye bye, cannot regap one.

My case, haven't try Iridium, but I used up 2 NGK GP plug within 3000km, not recommended.
Got a 2nd Racing Bee 3 tip plug, use until ground electrode also corroded.
NGK copper standard is the best IMO.

The MJ is small, PJ is big. Both ends become lean.
I don't know what's the standard jetting.

Paling lama 6 bulan must tukar, because exposed to moisture already, the additives in EO will degrade over time.

Bukan macam ini mia... read the plug, and determine only if you need a hotter or cold plug.

Overheat the plug, meltdown.
Overcool the plug, fouling and poor combustion.