Ah, it's all clear now! I think i'll just try to use as much of the original Honda stinger pipe as possible and see how i get on, there's nothing to lose!
How about that nylon block for the NSR250 carb conversion Andy? Is it needed for clearance purposes or is it to help the carburettor work properly?
Also, i have a bit of a stutter/hesitation at about 5-6000 rpm on my NSR150RR, i'm going to rebuild the carb, fingers crossed this will clear it up,
Cheers!