The best plan for any NSR150SP owners out there is to, at the very least, fit a pipe. the stock pipe is restrictive (It's got a cat don't ya know) and weighs a ridiculous amount.

Our carb kit is basically a modified NSR250 MC21 carb and manifold block. It bolts on with the minimum of grief and gives a couple of ponies.

More power can be had with a bigger carb for sure. Any of the PJ or PWK series Keihin carbs will work, but remember that the bigger you go the more bottom end you'll lose. throttle response at low rpm will also be noticeably worse.

Go above a 34mm carb and you'll have to start considering crank case modifications to increase the inlet area, so as to take full advantage of the bigger juicer.