Line Art: 1995 Honda NSR500
We feel we’ve wasted Mick Ofield’s beautiful line-art over a single page – so here we go… From this issue, have a spread of this amazing artwork. This issue, we look at the 1995 Honda NSR500 Grand Prix race machine.
IN DETAIL:
The NSR500 brought Honda to a period of total domination of the 500cc World Road Race Championship by the mid-1990s.
In 1984, Honda wheeled out their first four-cylinder two-stroke race bike. Like the NR500, some radical ideas were incorporated – the fuel tank being under and the exhausts going over the engine to achieve a lower centre of gravity, thought to improve handling. Freddie Spencer’s initial impressions were negative, with the lack of ‘pitch’ not loading the front tyre enough under braking.
For 1985, both the engine and chassis were redesigned, now looking more conventional.
To reduce internal friction, all Honda NSR500 engines used a single crankshaft, saving the extra main bearings a twin crank design required.
1987 saw a major engine design change, the angle between cylinders was opened up to 112 degrees and the reedvalves and carburettors were positioned in the V. ATAC exhaust chambers (additional exhaust volume accessed by valves to increase power spread) were ditched in favour of electronically operated ‘gates,’ effectively altering the exhaust port heights.
With the redesign, Australian Wayne Gardner won the 1987 500cc championship and in 1989 Eddie Lawson defected from Yamaha to Honda and won the championship, in that same year Mick Doohan joined Honda.
Chassis development was aimed at trying to tame the on-off power characteristics of 180+bhp. An engine redesign in 1992 saw the counter-shaft driven from the middle of the crank rather than the left end.the angle between cylinders remained at 112 degrees but carburettor size increased to 36mm with reeds suitably altered. Up to this point, two cylinders fired every 180 degrees of crank revolution.this firing order was thought to be contributing to rear tyre spin and grip, leading to vicious high-sides.
Different firing intervals were experimented with, resulting in the ‘big bang’ engine. Firing the cylinders closer together gave the rear tyre more time before the next power hit.the firing interval was closed up from 180 degrees to 68 (not officially confirmed), leaving 292 degrees of ‘settle time.’test riders thought the new engine was slower, but lap times showed the big bang idea worked.
Concentrating firing impulses so close together though increased stresses in the gearbox, clutch and crankcases.
“BY 1994 THE NSR SUITED A NUMBER OF RIDERS, THANKS TO THE ‘BIG BANG’ FIRING ORDER. DESPITE THIS, FROM THAT YEAR MICK DOOHAN WOULD DOMINATE ON HIS FACTORY NSR.”
Engines had to be thoroughly examined after every practice and the magnesium crankcases changed after just 600 miles.
When the new NSRS were fired up at the first 1992 Grand Prix at Suzuka, Japan, rivals were mystified by the deep exhaust sound. Doohan won the rainsodden race by 30 seconds and won the next four Grands Prix, was narrowly beaten by Wayne Rainey at Cataluna but won again in Germany. However, a badly broken leg at the Dutch TT nearly finished Doohan’s career and ruined his chance of the championship.
Crew chief Jeremy Burgess and a still-injured Doohan spent the winter convincing HRC to not change much and carry on in 1993 with a 1992-spec NSR.
One significant upgrade was a forced air/pressurized intake system aiding top speed.the chassis had minor changes aimed at improving turn-in and stability. Fuel injection was tried but did not give an advantage and was quietly dropped during the season. Kevin Schwantz won the championship, the best NSR finishing 3rd ridden by Daryl Beattie.
By the 1994 season the NSR had been honed into a formidable bike, the overall chassis geometry suited a variety of riders, as did the big bang engine. Burgess persuaded HRC to concentrate on useable rather than top-end power and to keep changes to the minimum.the result was Doohan winning the 1994 championship for Honda after a drought of five years.
The next five years became the Doohan/nsr era, winning five championships in a row. Honda rider Alex Criville was starting to hound his team-mate Doohan in 1996, bringing about a surprising change to the latter’s bike for 1997. The big bang had closed the talent gap between riders.to redress this, Doohan asked to revert to 180-degree firing order, the ‘screamer’ engine. Programmable ignition, revised cylinders, pipes and Doohan’s superior throttle control (he famously told a reporter, while pointing to his right wrist that ‘this’ was his traction control system) was a winning combination for both 1997 and 98.
Those two years saw NSR500S filling the top five places in the championship.
A career-ending crash in 1999 ended the Doohan/nsr domination.
NSRS won two more championships in 1999 (Criville) and 2001 (Valentino Rossi) before four-strokes heralded in the Motogp class in 2002.