What pipes are you using? Out of all the mods I have done, the pipes made the second most dramatic difference (the overbore being the biggest). And that was just a switch from the early JHA versions to a set of Tyga GP's.

Just cleaning up the ports and modding the exhaust as I described doesnt make a huge noticeable difference. But here's why: the biggest difference felt starts at 6k, and that difference will go all the way to 12k. Because the midrange is beefed up, the peak doesnt feel much higher even though it is.

Also, what are you setting your squish at? Going less than 1.1mm with the stock SE/SP combustion chambers puts the compression ratio and squish velocity less favorable for peak power and more prone to detonation. If you want to stick with .8mm like the GP bikes, you really need to reshape the combustion chambers. I had a 2000 HRC RS250 that had stock combustion chambers almost identical to ours, but the modified spares I had with lower CR and narrower squishband were much better on the track (and much more reliable).

Also, the stock airbox is a peak power hindrance. Not just the airbox itself, but the rubbers between the carbs and the box. Open carbs and a pair of those cool bolt-on venturies for the NSR are probably the best way to go for power, but you risk engine damage from unfiltered air. I have my airbox heavily modified, and it works just as well as open carbs now, while still using a filter.

And finally, jet kits. I am no fan of the jet kits for the NSR. I have tried them (using the stock oil injection system) with nothing but poor results. Major spooge out the pipe (too rich at low RPM) and degraded midrange power. The best way to go is to get adjustable needles and tune all the circuits as you normally would, retaining the powerjet system.

Almost forgot: reeds. I have found nothing that works as well as the Tyga (or equivalent) Carbon fiber reeds on the stock cage. And I have tried all kinds of combos. The carbon fiber reeds are the only ones that kept my engine from falling on its face at 11,500 without hurting midrange, regardless of my engine/pipe/intake combo. If you can get a set of V-force cages that will fit, or a larger reed cage assembly like the HRC RS250 uses, that may be the only better alternative. I myself am searching for a set of V-force cages that will fit our bikes.
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Paul Herr
'88 FZR4/GSXR/YZF Frankenbike
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