I would imagine the NS250 would respond to rather more taditional methods of tuning, but I haven't ever even seen one, let alone seen inside one!
You're certainly going to need to get some barrels to play with, or bite the bullet and pull your barrels off for some investigation.
I know the ATAC system was never that efficient on any of the motors it was used on, and imagine it's pretty much the case with the NS250. A set of race pipes and larger carbs (the MC18/21 carbs can be modded to fit the NS400, so maybe possible with the 250 too?) and some slightly more aggressive porting will all probably help things.
I'll see if I can find some info, but I think any race parts and books for them are long gone! I think RS250 ND5 parts may be worth looking for to give you some ideas of where to go.
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Andy.
NSR-WORLD.COM
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