AMAZING RESULT
“BUT AS WITH THE 500, THERE WAS A GOOD STRONG SURGE OF EXTRA POWER, THIS TIME FROM AROUND 10,000 REVS, WITH 12,000RPM AS A CONVENIENT SHIFT MARK.”
Freddie scored points in every round on a bike that amazed onlookers from the very first race with its turn of straight line speed – even if Toni Mang’s Sepp Schlögl-tuned factory-supported RS250R was on occasion just as fast. How fast is that? How about 278kph according to both HRC and independent speed guns – or put another way, as fast as most privateer 500s. Indeed, at most GPS in the 1985 season, Spencer would have qualified in the top 10 for the 500cc race on this incredible half-size motorcycle. How did Honda do it? A revealing talk with the man responsible for the bike’s development, HRC director Yoichi Oguma, on the day I rode it at the Suzuka circuit early in January 1986 proved very enlightening. “Our main concern was to make the 250 as similar as possible to the NSR500, since Freddie was riding both bikes on the same day throughout the season,” explained Oguma-san.” For this reason, we used the same cylinder dimensions and porting for the 250 as for the 500, even though the reason we used the longstroke engine configuration in the 500 (to save making the inline engine too wide) was no longer a problem with the 250 twin. Though we used 38mm carburettors for top end performance on the 250, instead of 34mm or 35mm on the 500, this does not narrow the power band too much, especially with Honda’s ATAC system fitted. Must keep revs up more on a 250 that is all.” So I discovered when I ventured out on the track that afternoon session for my own personal attempt to make like Freddie and hop straight from the awe-inspiring NSR500 on to the less powerful but no less successful 250. Straightaway I understood what Oguma-san had meant: just sitting on the smaller bike, even though it has a shorter wheelbase than its big sister, felt uncannily like being on the 500. In fact, although the riding position was near-identical, the weight distribution of the 250 was different with a 53/47% forwards bias without the rider, compared to 55/45% on the bigger bike. With a rider of Freddie’s 68kg weight on board the frontwards weight bias was evened out to
50/50% front and rear, compared to 53/47% on the 500. That balanced weight distribution on the NSR250 was distinctly unfashionable back then compared with far forward weight bias of its Jj-cobas and Armstrong class rivals, for example. The reason wasn’t hard to find: the 90º V-twin engine of course weighs a lot less than the V4 500, so by putting the engine in the same relative position in a similar frame to the 500’s in order to make Freddie feel at home, Honda inevitably ended up with less weight up front, and less than the optimum amount required by the Michelin radials. Honda tried to counteract this by tipping the engine forward, so that the front cylinder pointed towards the ground rather than horizontally forward as on the RS250R, but the main compensating factor was Freddie himself. Look at most pictures of him riding the 250 that solitary season that he raced it, and you’ll see he has his body weight pushed further forward over the front of the bike than was generally the case with the NSR500. A longer swingarm than the 250 production racer also helped matters. As with any 90º V-twin, even on this stroker it paid to push back on compression on the first cylinder, in which case the NSR250 would fire up almost at once – much easier than a Rotax, for example, which doubtless helped explain Freddie’s all-important flying getaways from the dead-engine pushstarts still prevailing in 1985.