I'm planning on getting a taotao 250d ATV or Vbike 250-V4D and after reading many post
I'm thinking the following should be done to the V4D / 250D when I first get it.
but have a few questions? Any help is greatly appreciated.

1. Use premium gas

2. Change out the spark plug to a (NGK) NGK D8EA (cost: $4)
do I need to adjust the gap? .02 - 025?
? is their another brand that is better and what model number?

3. Change the oil and use a synthetic oil (cost: $20)
? any suggestions on the best brand?

4. locktight all nuts (cost $15)
are their any problems doing this? should I use a torque wrench on the nuts and if so at what torque?

5. New Chain (428H KMC with 3/4 inch max play) (cost: $15)
? I noticed the max *** is 150 for this chain. Since this will be a 250 CC , do I need to consider a different chain? 118 or 120 link?
The 520H chain is for a 400cc max ATV so is this a better choice and will it work?
? what is the best chain to consider brand and model?

6. Change the front sprocket to a 13 or 14 tooth (13 tooth front JTF259 sprocket) (cost: $10)
a. should you also change out the rear sproket at the same time to ensure a quality sprocket? or is this not needed? Is this a simple replacement?
would it help reduce chance of chain comming off?
b. if the bolts touch the chain with the 13 tooth, doesn't this cause problems later on? should I go with a 14 tooth instead or is the 14 tooth too little of a change from the current 15 tooth that comes with the ATV.
c. also is a chain tensioner recommended and if so what brandand model.

7. Any other suggestions I missed?
Do I need a back up battery (if so what brand and model)
When I need to replace the tires will any 8" brand tire work? Can you change them out to 10" tires or does this cause other problems?
anyone know of a good swing arm bushing that will fit?
should I get a set of nuts to keep on hand incase I loose one out on the trail?

I know this sounds like a little bit of work but I'm hopeing to to be able to do about $100 in upgrades and have a pretty good reliable ATV.

Thanks