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The 1984 Honda NSR500 (NV0A) was a radical, "upside-down" experiment that redefined Grand Prix engineering through sheer audacity. To lower the center of gravity, HRC engineers famously swapped convention: the expansion chambers snaked over the engine where the tank usually sits, while the fuel load hung precariously beneath the crankcase.

This 499cc, single-crankcase V4 utilized a unique reed-valve induction system, but the underslung weight made handling notoriously unpredictable as the fuel load lightened. Despite its "experimental" temperament, Freddie Spencer’s surgical precision extracted its raw potential, taming a chassis that fought to wheelie under the massive heat of the overhead exhausts. It remains a carbon-fiber and magnesium monument to a golden era where HRC innovation pushed the mechanical envelope to its absolute breaking point.

 

And it didn't work. They found that with fuel cell under the bike, it resisted rolling over during the transition from one turn to the other. Turned out, having some mass further away from the center horizontal axis helped. And the exhaust routed above as mentioned, absolutely cooked the rider regardless of how much shielding they had.

Hence the 1985 NSR500 that Freddie rode to the Championship while simultaneously winning the 250 Championship.

Fuel on top, exhaust below. Single crank V4.

 

Thanks, Capt! Seems a little odd the factory engineers didn't get that feedback from their riders until they were into the racing season.

Maybe there are some things that can only be known in a race environment.

 

I think at the time Freddie was on another level and found things on the edge that test riders might not have or couldn't conceptualize.

It would be interesting to ask him.

 

Maybe he just needs an invatation to join VFRW?

He obviously has a lot of experence on a variety of V-4s.
If I understand correctly, he had a fleet of VFR's for his riding school.

Anyboty have his contact information?

 

He had one VFR (the one he rode) and a fleet of CBRs, that I'm sure were thru some kind of deal with Honda.

I attended his school 3 times. We even rode XR100Rs half a day working on flat tracking skills. Some students were really pissy about that, I thought it was fun and beneficial.

Even got to ride on the track with Nicky Hayden one of the sessions.

 

Thi

I think the engineers thought that lowering the centre of gravity by placing the heavy fuel load down low (I think those 500s had 32 litres of fuel = 25.6kg) would speed up the turn-in speed and help bikes enter corners faster.

Turns out, bikes don't steer just by leaning over on the contact patch, you have to physically move the front patch out and away from the turn to initiate the roll, and when that happens the roll isn't at the contact patch but through the bike+rider's centre of mass. That will be much closer to the crank shaft than the road surface. Thus began one of the current mantras about mass centralisation, and one of the reasons why the V4 layout is still considered close to optimum because it positions all of the heavy bits close to that centre. Modern GP bikes have fuel cells that are as close to the centre as they can physically be, to minimise the change in weight balance during the race.

 

2nd real ride of the season. First was yesterday on Easter when all the suckers were in church or brunch. It was nice.

This is about an hour ago.



This is now

 

Looks like it was a glorious day …


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