Alastair's NS400R Parts Book Resource

The predecessor of the NS400R, the attractive MVX250F. If you own one of these bikes, I'd like to hear from you.

1984 saw the release of Yamaha’s RZV500R 2 stroke V4 GP replica for the street. This generated huge amounts of interest at the time and the successful release of this bike and Honda’s 2 stoke 500cc title in 1983 encouraged Honda to release their very own 500cc GP replica in 1985. Suzuki released their own GP weapon for the street too in 1985, the awesome square four RG500. To take advantage of the Japanese market, the main market for these bikes, Honda and Suzuki released 400cc motorcycles. Whilst Suzuki also released a 500cc version for Europe, Honda sadly did not. This must be one of the greatest disappointments for 2 stroke race replica enthusiasts as with a full 500cc motor, the Honda could easily have been clearly the best of the 3 bikes. Broadly speaking, the Yamaha was an indifferent handling motorcycle particularly once the rear shock had warmed up but had a peach of a motor with heaps of torque as well as the essential 2 stroke characteristics. The Suzuki handled well and had serious horsepower, too much for many. The Honda was easily the best handling of the three and was reckoned to be the best handling motorcycle ever released at the time. Many scribes have since stated that the Honda was the first motorcycle to handle in the accepted modern fashion. The downside was the 400cc motor which was well down on power compared to the other bikes. Counting in the Honda’s favour, as noted above, was that it was a beautifully presented machine with build quality well above the Suzuki and Yamaha but it had a price to match. The NS400R was Honda’s first aluminium framed street machine and it remains the largest street 2 stroke ever made by Honda. Given ever tightening environmental legislation which has effectively killed off the 2 stroke as a road going powerplant in all but very small applications, it is likely to remain so.

Honda's NS400R was sold between 1985 and 1989. It is likely that the 1989 registered bikes were old stock. There were few changes during the production run. The original bikes suffered from a gearbox that did not latch properly into first and second. This was cured by a Hondamod on later bikes and this certainly improved the gearbox action. Sadly the earlier bikes were not subject to a factory recall which they really should have been as the early gearboxes are prone to disintegrating. 2 basic colour schemes were produced with minor variations depending on country of destination. The first was the HRC colour scheme which replicated that used by Freddie in 1983. The second was the later and by then current Rothman's colour scheme on the NS500's of Wayne Gardner and Ron Haslam. Variations on the HRC bike appear to have been confined to a different positioning of the yellow race number panel for the German market. The Rothman's bike acquired Rothman's stickers for the Japanese market while the rest of the world made do without. In some markets, a premium was charged for the Rothman's colour bike. The Japanese market bikes were restricted to 59hp to comply with legislaton there. The restriction took the form of exhaust restrictors and in some later cases electrical restriction in the speedo. Japanese bikes also had a different front fender design to that used elsewhere. The South African bikes had a different engine size as noted below.

The question might well be asked why Honda and others chose to sell GP replicas in the first place. With the benefit of hindsight, neither Honda nor Suzuki would probably have released such bikes. Impending environmental legislation meant that the strokers were a dead end commercially. They could not be sold in the US market, the largest market for such machines but solely in the European and Japanese markets. The large capacity 2 stroke has always been a specialist machine. Few motorcyclists are prepared to tolerate the rigorous maintenance a stroker requires to maintain reliability, fewer still appreciate the voracious appetite for fuel and oil or the furious power delivery which typifies the breed despite the successful employment of power curve modification devices on all 3 bikes. As a result sales were low for the Yamaha and likely much lower still for the later Honda & Suzuki neither of whom had quite the same 2 stroke quodos as Yamaha. Whatever the justification for making these specialist beasts, we can be glad they did for the motorcycling community would be poorer for their absence.

For an overview of the technical features of the bike, you could do a lot worse than read the Technical Features section of the workshop manual. In considering the technical side of the motorcycle it is instructive to consider that of the 3 500cc replicas, the Honda was the only one to use a single crankshaft, the most elegant and low friction method and that the NS400R was an early application of the then comparatively new Nicasil cylinder coating process. The use of a single crank V motor also enabled a neat installation of carburettors nestling inside the V in contrast to the messier arrangement of the others. The only innovation the bike lacked was an exhaust port height varying device along the lines of Yamaha's YPVS system which was far more effective than the ATAC system fitted.

The South African Bikes

In the history of the Honda NS400R, we cannot ignore the South African bikes. The South African version was a special run of 50 motorcycles with one thing in mind, the race track. 50 motorcycles was the number required to homologate the type for production racing and as the class they were to compete in was the then 550cc class, the 387cc stroker motor was too big to qualify. Surprisingly, Honda made a series of 373cc motors by reducing the bore by 1mm. The pistons used were NS250 pistons and it is likely that there was some commonality of cylinders. The airbox covers on the South African bikes were drilled as standard. This was allegedly done on board the ship before they landed so the modification could not be contested as a local modification. Quite how this was done without arousing the suspicions of customs is a mystery. Whatever the reality, if your bike has a very neat set of circular holes cut in the airbox cover in the middle of the squares on the inside in the pattern of 2 holes at the top followed by three on the next row follwed by 2 holes and so on, you probably have a South African bike. However, you can guarantee that now I have revealed this official modifiction both here and on other forums, this mod will appear on non SA bikes making identification more difficult. You can confirm South African bikes by reference to the frame number/engine number and the instructions to the parts manual which gives the frame number sequences. It was rumoured that the standard ignition was also different to those used in rest of the world but there was no obvious external difference so this is difficult to verify. Certainly there is no different reference in the parts book. What is known is that there were special sets of HRC ignition boxes floating around but as they were illegal under the competition rules, they were never officially acknowledged. The NS400R’s ruled the track from 1986 to 1988, three full years with modifications to the exhausts, rear shocks and blanking off of the power jet.

NS400R - The History & Background