since u wan mod already might as well put 62 with high cam, ori carb setting balik if dont wan change.

Good. Ori head more durable.
Like crappy123 said. Better upgrade to 62mm and highcam.
FZ block performance same like standard even you change to flat piston.
Ratio is good enough.

UMA good enough. On budget side you can pick SCK.
CMS & X1R problem for now.
Y15 engine same like 5 speed. No need to change rod. Original rod can withstand until 65mm.
Except for 4 speed. Need to change rod.

1. Can use back
2. Can use back
3. Can use back
4. It's up to your budget. High cam and 62mm sure will increase your top speed usually 160-180kmh. 62mm only will increase your pickup and top speed around 140-150kmh.

When install a high cam you need to install stiffer valve spring (racing valve spring) because to prevent floating which known as valve and piston hit when in high speed.
Don't know if your place have SCK or MDS. It's more cheap than uma.

Batam indonesia, if u have a time, u can go to Johor region if u want to find more products and brands. I'm not prefer UMA Racing, since the brand was expensive. ahahaha.

For me, no problem if u use any brand. the most important, piston type, piston pin, and the way u setup and setting ur spec. As long u make it tidy and follow the rules, should be no problem.

But if u are the speed hunter, "hati kering" wants more speed. U need to think about the durability each brands and products.

1-Conrod - U can use back, as long it was not too loose or can pull up or push down at the crankshaft.

2-Valve - Can use back, but prefer to do re-grind valve in order to prevent lose compression or "valve bocor".

3-Head - can use back, better with port the intake and exhaust. the inlet follow the carb size. better performance. If u have more money, can change to bigger valve, 19/22. adjust compression ratio. Lay the head about 0.4mm - 1.00mm max.

4-Camshaft - Preferable to change big lift more than std. Mostly Indonesian product, they high lift but small duration. More to pickup and track session but not topspeed and long distance type. In Malaysia, use CMS T2, as cheaper and easy to find. Can support pickup n top speed, long distance.

Camshaft have many profile, i can share with u if u want.

5-Cylinder Block - SCK, the quality were great but need to see the pin piston, because if u want to change a new pin piston, u need to go to machine shop to cut or adjust. SCK pin piston not same with other type.

MDS also good choice, cheaper than UMA, can be considered too, but please check the piston material n everything.

CMS can be use because have two type, forged piston or std piston. but the price a bit higher than other.

SBM rare block, but very good quality plus have the deeper water space.

KFC block also good but rarely to find.

P/s - For myself, i'm prefer MB (Malay Bengkel) Block. Tested for long, track use, and also the engineering idea are good. two choice, std piston or dome piston.

Save your budget on ratio. It's not easy to install because required to overhaul. DIY will save money but shop will cost money. Better wait when you need to change your rod. Do it one time.
For top set, install it one time which is block, hi cam and valve spring. It will cost money if you do 2 times. Gather your parts slowly.
You can install carb and cdi later.

Nice items, but better u gather all part before u install it, or it will be double or triple cost. Prefer 1 shot cost.
May i know, SP Carb? what kind of carb is that?

Gearbox ratio, what do you prefer? Wide ratio (High RPM gear change - Long) or Narrow ratio (Low-mid RPM gear - Short) or STD but power?

U can change ur GB 1,2 & 4 or Fullset gearbox sprint or Highway or u can lay ur 4th GB. I'm currently use the lay of 4th GB. High RPM top respond, no "lemau".

For Conrod - SCK, arata or other AF brand were expensive and not sure the durability. For myself, i modify my crankshaft to install the FZ/5S/Y15ZR rod, instead of STD OEM. If u know the brand "LONG ROD". I use this one together with harden the rod. So far so good, convoy, "Larian Amal", almost 2 year, seems like no problem at all.

Just my recommendation. No need to follow if you have set your target.
Go for original FZ/5 speed/y15 rod. Need to cut crankshaft 1 mm side by side.

Yes possible to pnp. Forged rod is there. I forget to recommend this.

CMS or Arata. Yes true pnp. No need modification.

5-Cylinder Block - SCK, the quality were great but need to see the pin piston, because if u want to change a new pin piston, u need to go to machine shop to cut or adjust. SCK pin piston not same with other type.

MDS also good choice, cheaper than UMA, can be considered too, but please check the piston material n everything.

CMS can be use because have two type, forged piston or std piston. but the price a bit higher than other.

SBM rare block, but very good quality plus have the deeper water space.

KFC block also good but rarely to find.

P/s - For myself, i'm prefer MB (Malay Bengkel) Block. Tested for long, track use, and also the engineering idea are good. two choice, std piston or dome piston.

Online shoping
- http://motor-part4u.blogspot.my/
- http://chmotorcyclestore.blogspot.my/
- http://syark86-pma.blogspot.my/

This 3 is reliable seller. I have buy many parts from them. They will post it.

Good.  
Start from
MJ (mainjet) - 150
PJ (pilotjet) - 38
Air screw - 1 1/2
Needle jet - no 3

Need to do plug check. Brown plug color is the good tune. White means lean. Black means rich.
White need to up your MJ/PJ.
Black need to lower your MJ/PJ.

Plug check
Outer of plug - for PJ
Inside of plug - for MJ
If unsure you can upload your plug picture here.

depends on your luck normally if its thai ori 140 bucks. u be like riding horse.