A lot of people press the stem out of the NSR yokes and into the yokes they're intending to use with whatever front end they have... That is absolutely fine, IF the new yokes have an offset of 35mm...

The NSR yokes have a pretty large offset at 35mm... For instance, Harris' adjustable offset yokes only have a range of 24-34mm... The offset is the primary way that the trail is determined and even a very small change can have a large impact on increasing or decreasing the trail. The conversion I've just done with the ZX6rr forks wouldn't have been possible with their yokes. The offset was 20mm... This would have increased trail from 87mm standard to 98mm. Doesn't sound much, but it would sure slow down your sweet handling NSR.

As Andy points out, it's not quite as simple as just swapping it all over, IF you want to do it properly.

You CAN partially overcome the increased trail, by reducing your rake, (increasing rear ride height, rasing the forks trhough the top yoke), but it's a comprimise.
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NSR300R - Why did i ever have a 250...