1989 Honda RC500M


1989 Honda RC500M

The most powerful Motocross bike ever built

In the 1980's Honda was the most dominant force in Grand Prix motocross. Their effort was financed by an almost unlimited budget and they produced by far the best bikes and had the best riders. Especially in the 500 class. It wasn't a question as to who would win the title, it was a question of which Honda rider would win the title. Eric Geboers is one of the greatest motocross riders of all time. He is a five time World Champion and has been World Champion in all three classes. This alone is a testimony as to what a talented rider Eric was. 1988 reigning 500cc World Champion Eric Geboers campaigned this bike in the 1989 500cc grand prix's. This was Honda's last attempt at an all out 500cc 2 stroke grand prix works bike. The bike appears to be production based, but in actual fact very few parts are production. Only the plastic and a few engine parts are production. The rest of the bike is hand made. The 1989 RC500 also known as an NT8, sits today in unrestored condition as Eric last rode it.


1989 Honda RC500M Photos


Eric Geboers' comments:

This 1989 RC500 is a bike that I have produced a lot of sweat on. I was successful at convincing the Japanese engineers to come to Europe to develop the bike here. From prior experience we knew that testing in Japan was much different than testing in the environment where the bike would be raced. Honda of Japan's strategy for 1988 and 1989 was to start with a production style frame and engine cases. Starting like this makes it much more difficult because you are limited in some key components. In prior years frames were custom made just for my size. For this bike the frame had to remain the same size as the production one, although it was modified. We put more hours in research, more man hours in engineers, more engineers at the track and more hours in track testing than any other bike before. No other bike had consumed so much attention as this one. The direction I went in, more than any other rider, was to make the power usable. I wanted all the power converted to acceleration. If I opened the throttle 20%, I wanted 20% of the power to the ground. This is very difficult to do with a 500cc two stroke. It is very easy to have so much power that it is impossible to control. With a 125 or even a 250 this is not such a big issue. But a 500 with uncontrollable power makes the chassis and the suspension bad as well. I wanted the shape of the powerband to be very linear. I got in many conflicts with the engine engineers at first. They wanted more compression and bigger carburetors for maximum power output, but this produced uncontrollable power. In theory it looked like the way to go. In reality on the racetrack it resulted in slower lap times.

Just before the Finnish Grand Prix, I suggested we do a blind test. I said," Build me three bikes and don't tell me what is on each bike. I will ride all three bikes during practice and I will tell you which bike has the smaller carburetor and low compression". They agreed. After riding all three bikes in practice I told them which one it was and I was right. My lap times were several seconds a lap quicker on that bike too. I opted for that setup on the Grand Prix bike. What really threw them out of their chairs is when I got the holeshot in both motos.

I was working at perfecting the powerband all year long. I even went as far as testing 24 different crankshafts. David Thorpe and I were allotted 12 crankshafts each for the season. Even though each crank was new and within the specified tolerance, I tested each one separately. You could feel the difference from one to the other. There were three that were so good that there was no engine vibration at all. This made the bike feel well balanced. I kept the best ones and put the rest back. David Thorpe will not be happy to read this! (laughter) So I had three good cranks for twelve Grand Prix's. The problem was that Honda demanded that we change the crank every three Grand Prix's. Since the three were better balanced than the others, we cheated a bit and used them for four races each. I didn't win the title in 1989. That was kind of a strange year for me. I carried the number one plate, but the biggest mistake I made was the choice of tires. For ninety percent of the year I used Bridgestones. They provided excellent straight line traction and were very good for cornering, but on any other part of the circuit that gives quite a bit, the Pirelli moose set up was far superior. I tried the moose set up in 1988, but that was with the 18" rear rim. On the 18" rims they felt kind of floating and were not as stable as the conventional set up. 1989 was the first year for the 19" rim and that provided a lower tire profile. With the lower profile, that removed the floating feeling and was a much better set up. I completely underestimated the performance on the 19" moose set up. My main competitor David Thorpe made the right choice by going with the Pirelli moose tires. By the time I realized it, it was already too late. The Championship was already decided. I had the bike working so good. The motor was perfect, the suspension and frame geometry was perfect, I just made the wrong tire choice. It was a shame to spoil the year after so much work and to disappoint so many people, but this was my mistake.

Much of the technology learned in 1989 was carried over into 1990 and beyond. My 1990 works bike was very similar to this one. I pretty much dominated that season. And was World Champion again.

Getting behind an RC500 at full throttle would be taking ones life in his own hands. The 1989 RC500M is probably the most powerful motocross bike ever made.

 In 1989 it wasn't a question of who whould win the 500cc world championship, it was a question of which Honda rider whould win. Eric Geboers and David Thorpe at Namur Belgium.


Detail Photos


 

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Historical Photos


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