Further to my post I can add a bit more. To be clearer, my performance parts were obtained online at the Tyga site and included the Tyga exhaust (expansion chamber and aluminium siencer), carbon reed valves and step kit (alloy rearset foot pegs and linkages). The other modifications were done by me and included the bigger carburettor (32 mm Keihin) air box and intake mods, main jet from 152.5 to 157.5 and checking the ignition timing, oil pump calibration and a few other minor things.
I use 98 octane fuel and synthetic racing 2 stroke oil. It accepts low octane unleaded or even small doses of ethanol but performace is lower. I wouldn't ride hard with low octane fuel as I believe the risk of engine seizure is greater. For high speed riding and track days I put 36 PSI in the tyres but this is a personal choice as a 76 kg rider. There is little option for the alternate branded tyres (such as Pirelli or Michelin), particularly the front apart from Dunlop rear and standard IRC front. There may be other brands available in some countries. the next steps for mods may be a Wiseco piston and some smothing of the intake and exaust ports with gasket matching and some triming of the powervalve to lower the exaust port floor in the fully open position. The other performance tweek is an alternate ignition control unit which is supposed to provide more power in the upper rev range. I would expect that its possible to extract 40 reliable rear wheel horsepower from the NSR 150 but this increase may reduce the interval between engine rebuilds from 30,000 km stock to 5,000 km.
The main weakness in the engine/transmission is the gears some of which, on my NSR need replacing after 25,000 km of hard riding. Also going quicker puts the brakes into question which lack feel and power from standard. I guess to extract more than 35 hp from any motor smaller than 200 cc is a case of diminishing returns as the same or better performance can be had from a 250 2 stroke or a 400 cc 4 stroke with better ride and more reliability.
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NOMEDEEPS