The stock NSR150SP promises so much, but is a real let down if you ask me.

The engine's weak and the handling isn't worthy of the NSR badge.

All is not lost though as they are primarily designed to run in bangkok traffic at low to mid rpm on roads that the Western World farmers would consider "rough"!

Good tyres are a must. The stock Bridgstone rubber is pretty good. The suspension needs stiffening up. Try some porridge in the forks, that might get you a little damping! Seriously though, some 15W oil will probably work better than stock. can't do much to the rear (unadjustable) except preload.

But I guess that you're more interested in engine performance.

You say you've already done some porting. Did you mess with compression? any crankcase mods? carb? you're in Singapore so I bet you're using the stock pipe for fear of Police harassment!

The stock engine settings are pretty low spec. you need a bigger carb, a good pipe and the breathing through the engine needs attention all the way from start to finish. The intake especially is very restrictive at high rpm.

you can also lighten the flywheel and trim down the balance shaft (don't take it out).

Apparently there's also trick CDI's available, but I've only ever seen an HRC one and wasn't allowed to touch it.

Just keep fiddling with it. there's potential in that little rattler, but you'll have to get a little savage with the grinder.