My bike use standard engine head, no valve, no cams, only spark plug hole.

Grind valve is when valve is damaged, and no money to change.
Porting means make the intake and exhaust hole and airway bigger.
Polishing just means make the airways smoother.
Cam lobe makan - Must replace. Can be caused by overheating or racing valve spring or low grade EO or EO too good.

Stock engine, don't do anything modding is the best. Bigger exhaust tail pipe is the best mod for stock bike.

If you change cam, you can consider polishing and exhaust. Spend all the time to make the new cam setting nice.
Later then big bore kit.

stock engine take care eo and oil filter wont get damage much. but long term sure got some minor wear n tear inside engine. luckily your name is suhai not sohai. haha

this is valve makan. the tip gets chewed off

depends on your budget. ori valve not bad can tahan weekend race. i havent try other brands so i dont know

racing valve as in difrent size ? ori is 19-17. i seen allot of cms racing head 22-19 cost 470-500. u have to buy the whole head.

really appreciate for your reply.

according to what i found, the v1 lc(2010) is using VN22 carb(from here) while the v2 is using BS25(from yamaha official website and also brochure). So i think the BS25 is the new carb.

Few years back i drove Suzuki RG. Actually i like Yamaha 125Z but i heard from afew motor shops said it is a very hot target for the motor thieves. And some said the FC is bad, and some even said the price of 125Z is over coz goreng too high dy. The reason why i like 125Z is because it is a 2T bike as i'm used to 2T bike and cluth. So the alternative of my selection where the bike with cluth is ES now. The v1 speedometer looks better compare to the v2(juz my personal pov).

I saw quite alot in mudah.my and call them, alot of them are sold.    So if the quality of both versions are almost the same, i think geeting a v1 is enough, juz w/o the 5th gear and rear disc brake.

I called those sellers, and i found a few options as below:
1) 2010 ES ~RM5000 - 28k mileage, everything standard.
2) 2008 ES ~RM5250 - 9k mileage seldom use, everything standard.
3) 2008 ES ~RM4500 - 37k mileage, already changed to bigger block and ecu/cdi(not sure which one), other standard.
4) 2009 ES ~RM4200 - 79k mileage, changed to 125z sport rim with rear disc brake, other standard.
5) got some other SS model, but will be last choice if cant get ES.

Of course i wish to get a lower mileage bike but not sure what is a reasonable mileage for one year. 10k km per year?

yamaha s6. stock valves, very syoik with uma block.

your white smoke, describe better can?
pomen already say block calar, right? How you expect us to help you with that little description you give?

use 60mm straight. almost same price as fz + upah pasang. bokbokbok memang semput. motor got shake shake when pulas minyak?

standard mod maybe is playing with electrical thing like shyan did 
btw
60mm better chg the rod , cam , valve spring all in 1 shot ... if me better chg the gearbox also so can get good top speed and pickup

60mm ak rembat [even blok tengah calar] in a week,check still not goyang...62 might consider if really need to overhaul[I do recommend and use TKRJ Japan or HiSpeed Thailand both have 14mm SE-Pin and may press on crankshaft],and might not to change rod [if rod still ok hahaha]

If kaya, then msuk piston Jaguh 65mm SE pin 16mm + crankshaft pndai2 la modi dgn rod apa..hehehe
In my opinion:
better take X1R ceramic...the finishing nearly same as Uma racing...But for me,I do change piston + ring [Brand apa? rahsia]

cms cam + cms valve spring = ok da tuh [Make sure ori] + if plus with carb...kapowww

Gear 4 21T:
Lot's my friend pasang and bukak balik...why?
pickup gear 4 cepat mendaki...tapi akan tergantung and menung...gear 4 std best lambat mendaki tpi akan x menung...

Compression ratio:
Kalau belanja teh ais...mudah nk terangkan wakakaka....Citer smpai esk x habis..
62mm... Ganazz