RD500LC and FZR400RR project


Updated : 03/05/2009

I've recently bought an FZR400RR type 4DX / 1993 in order to make a nice alloy framed RD500 for track day runs.

In this page I will try to give news from my project.
Last step

Photos (click to enlarge)


Frame modifications and radiator mounting. I've put individual filter but it is better to build an airbox. I've some technical papers to read first. Any advices welcome.

I've opened the FZR400RR airbox and I found that using the trumpets could be a good starting point for the design of the airbox. From what I've read the 2 strokes do not like long trumpet but short ones. This is a good point because the fairing will not fit with the FZR400RR trumpets on the KR1 carburator.

Fairing on for the airbox design

The airbox volume should be at least 10 time the engine displacement => 2.5 litres per side.
First test with a  14cm x 25.5 x 7 box to check the space in the fairing.
The air intake initially used for the cooling behind the cylinders could be used as the airbox intake.

I've planned to shape the airbox using polyurethane foam in order to validate the cross section. I'll measure the volume and it should be above 2.5l
With the fairing, I decide to remove an extra bit of the frame.
Frame cutted and tests with carb. and foam filter.
Airbox will be more easy to make.
An idea, use sone Venair MDT tubing in 50mm ID to connect the carburetors to an airbox behind the steering head. A length of 50cm represents a volume of 1l per carburator thus it will lead to 6l. Any comments ?
Airbox simulator : airbox is an Helmholtz resonator and its resonance frequency is linked to it dimension.  I've setup an OpenOffice Calc file to compute the dimensions according to volume, duct length, aperture height.
V=5l ; RPM= 9000; Length=3cm; Aperture HxW= 6cm x 7.7cm
Any comments ?
Steering head airbox.
main dimensions : 32cm x 8 x 4 = 1.24l
2 extra volumes => 1.6l
50mm tubing departures?
I've decided to change my mind on the airbox because I've a lot of electric stuffs to place. So I've decided to close the space behind the steering head and seal it with the front part of the tank. Thus, I could place the wiring loom connectors in the airbox, the coolant tank (maybe not a good idea if it gets very hot!!!).
Pictures (from left to right)
  • top view,
  • under view,
  • rear under view,
  • under tank view.
Here is the realisation in metal sheet (later this could be in alloy sheet). After cutting and grinding I finaly got the "airbox" done (pictures 1-4 & 6). I think I could used the FZR400 ignition coil holders (picture 5) if the metal inside does not need to be grounded. A neoprene strip will seal the airbox with the tank (picture 7). Last picture shows the 4 ducts departures and the YPVS controler. Need to confirm this.
Testing on how to make connections to the airbox.