Hi Freak370,
I guess you just want to hot the engine up, but in my opinion that's about 25% of the fun. Firstly it has to not break down, then it has to handle ok, lastly you need more HP.
Some ideas for you in approx order of importance:
* Engine: Just start with a quality air filter, a magnetic oil drain plug, frequent oil changes, and good jetting. After you get your bike handling ok, then worry about more engine power from cams etc.
* Remove and re-assemble most parts. Nothing will be loctitied, and nothing will be greased properly either. Many bolts will rust or bend. Shock bolts typically have the thread inside the bearing surfaces. Sort out this stuff first.
* Check the spoke tensions when new and after the first 10 rides. They usually stretch a bit then after a while, they'll hold pretty well.
* Get a bike with Marzoch copy (China made) USD forks. Flush the fish oil out (twice) using 5wt fork oil. Then (assuming it a mid sized pit bike) add in 275 to 285ml of quality 7.5wt oil (eg. Motorex). These forks can work REALLY well for the price! Stock fork springs suit a 75 to 80kg med/fast rider. Note the 10+ fork oils are for conventional forks or perhaps some really basic design USD forks. Forget the thick fluid in real USD forks.
* Don't even consider dampers (on either end) without adjustable compression and rebound clickers. The chances of fixed valving being right is near zero. Obviously no Chinese, Taiwanese, or Marzocchi dampers come close to the performance possible from well setup Showa, KYB or Ohilins. This is due to both design and quality. So you have to be realistic in your expectations. The Taiwanese (eg. Fastace, DNM) and Chinese stuff (eg. zocch copies) have quality control limitations (machining etc), so the performance can vary a lot in the same part model. The Taiwan and China products work heaps better with quality suspension fluid in them. A fluid change in a shock can cost more than the shock, but (like in the forks) the ride quality will be more than twice as good, so your decision.
* Use a rear spring which suits your weight. The front and rear sag should be suited so your bike turns properly. Hard to explain but try commonsense. Unless you weigh 80 to 85+ kg you should not need a 1000 or more lbs/inch rear spring, assuming your shock has decent bottoming control.
* Make a basic mud flap thing to keep the stones off your nice rear shock shaft. See pitster's 09 bike for some clues. Or search my old threads for "mudflap".
* Get some decent tyres for your target terrain. It makes a big diff. If you can afford the extra $20, then get some Bridestones, Pirrellis etc, since they ARE way better. Get a rim lock installed in the rear wheel and the front too, if you will ride softer terrain with tyre pressure below 15. The China rims dent easy so beware tyre pressure below 14 on anything but soft terrain with no rocks.
* Make sure your brakes work. Most stock china brakes can work REALLY well on the small wheels IF you put good fresh fluid in the brakes, and use healthy clean brake pads, and your master cylinder pistons are adjusted correctly.
* Keep an eye on your stock china wheel, and swing arm bearings. Once they start to die, get some good Jap bearings in there.
* Get some good grips. The ProTaper "Diamond" grips (dual density) from DHZ are only $20 and they feel GREAT to me.
