It's correct that there are many changes year-on-year for the NF5, some more significant than others, a number of which are effectively constrained to the particular model year (i.e. not interchangeable). Therefore it can indeed be harder to maintain and run an NF5 than an NSR. Be aware that it is also highly advisable to run an NF5 on AVGAS too, which can add to both the expense and [setup] complexity.

The NF5 power delivery, by the nature of its intended use, is peaky. Some years are worse than others, but all are peaky and make their power high iup the rev range compared to even a TT-F3 NSR. To exploit an NF5 it needs to be ridden very hard.

In my personal opinion, unless you are fast enough, or unless you really want an NF5 (or NX5/NXA), you are better off with a well tuned NSR. There's no reason why an well prepared MC18 R5/6K can't make over 65rwhp, and have substantially more mid-range drive than an RS, making it easier to live with/ride.
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Andy.
NSR-WORLD.COM

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