The RS250R NF5 crankcases are based on the 1987 NSR250R MC16 (the MC21 cases are purely an evolution of the MC16), and as I say, the F3 is all but RS, but with some mass production based limitations. The biggest inconvenience are the non O-ring heads, which again, rules allowing, can be fixed with VHMs. Also the RC Valve system has 4 cables, 2 direct to each power valve pulley, rather than the more precise dual cable/rose joint setup of the RS, which makes setting and operation a little less accurate.

The carbs are a compound unit, and literally pop off with 2 screws, much to the chagrin of many an RGV and TZR owner, so jetting takes no more than a couple of minutes. Needle changes are by way of quick release retainers, once the two screws on the cover plates are removed, again taking no more that a minute or two to change both. As the carbs are fixed side-by-side with a bracket, it makes one of the air screws a bit of a niggle, but in fairness, these are pretty much "set and forget" really anyway.

The NSR and RS transmissions are virtually identical, and mounted to the same transmission plate, so technically interchangeable, although the NSR clutch and drive are considerably heavier. There are some other minor differences, but irrelevant to this post. The point is that, once again, maintenance is almost GP [RS] like.

Ultimately, and very simplistically, the NX5 is "just" an evolution of the NF5, which was based on the MC16! If anything, the NX5 is slightly more complicated, given that it has a balance shaft!
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Andy.
NSR-WORLD.COM

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