Jeez - It's like you're all waiting for my little biatch to explode!
I've just set mine up safe 'through out' the rev range... So huge pilots (although that's the PJ38's for you) at #48 and #50, needles running at around 6% CO2 and the mains the same... I don't really worry about what sizes I'm running, just as long as the CO2 reading is above 5.75-6%... An RS or TZ250 on the edge will be as low as 2.5%, but i don't want to rebuild mine every 700Km...
I also went premix, so I know that it's getting the oil it should be, an many will increase the mains by 50% etc, and the pump doesn't compensate for this enough in my book. Again, I'm running 30:1 on TYGA's recommendation, although I could probably go with 40:1 to get nearer to the edge.
Mine made 71 with the standard carbs and 73 with the the 38's I've got now. But the over-rev has increased by about 700rpm, so at the top end, above about 11300, I now have about 10bhp more than the with the old carbs, although peak isn't that much different.
I've spoken to Graham File about bottom end tuning and the like at length now, and he's worked on a lot of 21's before, and with Dynotech, where i get my bike set up. He thinks i could expect around an 8 bhp increase in the midrange (up to 10000rpm), with another 3-4 bhp on top. This is without any crazy porting or any 250 style tuning to get similar power levels. The only thing you have to remember, is that your top end might be safe-ish, with these sort of figures, but the crank isn't going to like near 80bhp too much, and that power comes at the expense of pistons that are around 20g heavier (from memory) than the stock 250 ones... So extra strain again.
My main concern is reliabilty, as I'm a recreational rider, not a racer, so I had the option of buying a brand new top end, for half the price of the 250 one, and getting the sort of power than would cost me a couple of grand out of the box, with above average reliabilty.
My bike has cost me about the same as a good 2001/2 RS now, but I've paid it in dribs and drabs, (the worst way!), but if I'd have gone that route, I'd be forking out all the time for consumables that really add up in the long term.
I'm not going to say the 300 is better than the 250 as it's really a different bike now, with it's own merits. You can feel the extra weight in the engine, as it does rev that fraction slower, but in my opinion it makes up for it in other areas.
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NSR300R - Why did i ever have a 250...