“PROSPEC” explained by Matsuda

NSR250R Mania “in a nutshell” (1) [second part]

  • 2017/9/5

1. Methods in distinguishing between NSR “models” [second part]

This continues on from the first part that explained about the first three generations of models, with the fourth in-line being the 1990 NSR MC21. The strongest image of the NSR is the 1988 model, but if you take preference or tastes aside then you’ll find that the industry agrees on how the best out of the generations of NSR is the MC21. To the extent that when Honda announced the release of the bike it exclaimed “This MC21 completes the NSR”.

MC21 (1990 – 1993)

NSR250R MC21

Here are the characteristics of the MC21.

  1. “Gull Arm” swingarm shaped like the Japanese character “へ” (shape like a mouth)

  2. Diameter of rear tyre reduced to 17 inches (up until the MC18 it was 18 inches)

  3. Different style headlights used

  4. Frame shape changed

One of the reasons why the MC21 is known to be the best is because of its high performance in cornering ability. In contrast to the MC18 with its incredibly rigid frame that is sometimes a little bit difficult for the rider to make turns, this frame was made to hold just the right amount of flexibility. Furthermore, with the change to a 17 inch rear tyre this bike transformed into a machine “that can be cornered well by just about anybody”. Incidentally, in the NSR PROSPEC specialist magazine I had the 1993 WGP250 champion Tetsuya Harada ride all of the NSR models, and after sampling the MC21 his first comment was how “It corners in the same way as the Yamaha TZ!”.

Furthermore, the engine’s potential is also raised. With the use of the Gull Arm the degree of freedom in managing the expansion chamber rises, and the PGM (3) also evolves with higher intelligence. In theory, if one were to put a mint condition MC21 onto a dyno with its limiter de-restricted (granted that it is not like the 1988 model, but it is possible to de-restrict through a simple procedure), it would display the same power as the 1988 model at 57–58bhp, and output after the peak power rush would not be low, “having sorted the trait of over revving”. Not only is it powerful but it also has a wide power-band similar to the 1988 model, along with being easy to deal with like the 1989 model, so to speak.

Ways of identifying between the MC18 and MC21

Because of the alterations in balancing the overall rigidity, the shape of the frame is also completely different. The first thing that stands out is the difference in thickness of the frame. In contrast to the MC18 frame that is very bulky, the MC21 frame is pretty narrow. As already mentioned earlier, the sideways rigidity of the frame is lessened more than the MC18, so the appropriate amount of twist in the rigidity balances things out when cornering. Despite this, the height from the top and bottom of the main tube is enlarged, so the structure found in the vertical rigidity of the frame keeps things absolutely sound when under braking.

Despite the main frame bars being narrow in width, the whole body of the frame is wide. Furthermore, there are also differences in how things are made around the swingarm pivot area, and general amendments all over that alter the rigidity of the frame.

The MC21 integrates all of the strong points of the old NSR, and for the first time was the only model that didn’t receive a yearly model change, as its production continued on for four years until 1993. (Within this time there were only minor changes made to the spec). Despite being in the period that saw the fall in popularity of replica bikes, there were still around 43,000 units produced. It is recorded that a maximum of 12,000 exist today, so the MC21 is the NSR that was most in existence back then, and for the present day too.

MC28 (1994-1999)

NSR250R MC28

The fifth and final generation of the NSR is the MC28. This bike was born at a time when the popularity for medium-weight class bikes had already come about. Although it followed mostly the same running abilities as the MC21, there are various other characteristics that were introduced. The main changes from the MC21 are below as follows.

  1. One-sided swingarm “Pro Arm”

  2. PGM card key system

  3. New shape front forks and calipers

  4. Upper, tank and tail cowlings changed

  5. Digital speedometer (rev counter analogue)

First of all, the biggest characteristic change is the one-sided “Pro Arm” swingarm, a mechanism that had already been in use on the VFR400R NC24 / NC30 & VFR750R (RC30). Its appearance is outstanding, and it is common to see custom NSR MC21 models that also make use of the Pro Arm. Nevertheless, it seems that there was conflict with Yamaha prior to this regarding the patent for the Gull Arm of the MC21, so Honda was effectively forced into changing the swingarm design for this model.

Also, the MC28 used for the first time ever a card key system, that replaced the conventional key with an electro magnet bonding card (self starting kick starter). The card supplies engine control data like when firing up, and if one uses the HRC race use card that was sold back then then the capability of the engine can be increased. What is known as the “limiter cut” up to as far as the MC21, can instead be completed just by inserting the HRC card (however, because the speedometer is redundant you cannot run it on the public roads). On the flip side of such a new luxury like this being released, however, is the self limitation system that brings power output down from 45bhp to 40bhp (dyno runs provide similar figures to spec). In addition, in order to limit the speed to 180kph without a speed limiter, the gear ratios are shorted all throughout. In other words, if you try to make the MC28 deliver a similar spec as a de-restricted MC21, the bore chamber is suppressed in such a way that it that restricts the power output, along with the transmission area that is amended too. Furthermore, the ignition system is made to operate in such a way (ideally use the HRC card) that a fair amount of messing about would be essential. Therefore, one can say that putting in a self limiter results in a strong hindrance, because it takes quite a bit of prep time in order to release the bike’s full potential.

MC28 card key. By inserting the card in the slot below the clocks, the ignition comes on. For opening and closing the fuel tank cap, the ordinary style triangle shaped key is used (found on the top left hand corner of the card).

Nevertheless, it is still the case that there are many fans for such models as the Rothmans (1994 SP) or the Repsol (1996 SP) that are popular for their colours, awesome looks with the Pro Arm, or for the exterior design that is based on the 1992 NSR500. Also, such features include the new carburetor, (4) the more highly intelligent evolution of the PGM, the engine that is easier to handle, the fuel tank that is 25mm shorter, the wider seat, and the footrests that are set a little further forwards making the riding position more comfortable. The front calipers are a new design, and the front forks have more advanced damping structure that gives the SP a matured high end feel throughout, so one could say it seems most appropriate as a final NSR model. As expected for a bike that appeared after the replica boom the production of 6000 machines was a little bit low, but considering there are still nearly 5000 recorded today it really reveals how owners tend to take pride in looking after their beloved machines.

The Rothmans and Repsol sports colours are both very popular NSR models that are true icons of the MC28. Especially in recent years I feel that the Repsol, with its orange centre and contrasting blue tone (Honda call this Jerez blue metallic) is absolutely stunning, and out of all of the NSR models it has the best colour scheme. That’s just my own personal opinion though of course!

Ways of identifying between the MC21 and MC28

As mentioned previously the use of a Pro Arm on custom bikes has become a standard practice, so if you put a Pro Arm onto an MC21 which fundamentally has almost the same frame structure, then distinguishing between the MC28 becomes a bit of a challenge. Therefore, at this point of time I would like it if you could please examine the area around the swingarm pivot in the pictures below, just in the same way as with the MC18.

Pay attention to where the arrow points!

When comparing the tail cowling of the MC21 and the MC28, the front end section of the MC21 piece does not reach the frame, and you can see a little part of the seat rail. In contrast to this, the front end section of the MC28 cowling extends to run alongside the frame, and the seat rail is completely covered. The screw hole area is there in order for the tail cowl to be installed, because the MC28 frame is extended.

In addition, because it has a card key the MC28 does not have a key cylinder, so if you open up the hole behind the head-pipe section of the frame, you can see how the electric handle lock mechanism is stored here. From the outside you can’t see it, but these are the main differences between the body of the MC21 and MC28.

In order to store the handle lock mechanism on the MC28 there is a hole opened up on the backside of the head-pipe area of the frame. There is also a block up plate included for the hole in the case of using the HRC parts kit for the MC28.

Well, it all seems to have ended very abruptly in what I thought was meant to be a simple explanation about the five different NSR models, but I fear how I may well have drawn things out quite a bit! Incidentally, next time I plan to introduce the colour scheme variations from each year. These days it is natural to sense the difference in age with the exterior of the NSR models, so I would like to report on ways of detecting such areas.





■愛車:HONDA NSR250R(1992)/HARLEY-DAVIDSON XL883(2009)

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