F400 Suspension Regulations

[phildawson8270]

Ok so not strictly a ZXR400, but hopefully one of you guys will know the answer.

So far the build for a Formula 400 bike has being going quite well to try and be ready to join next year, however I hit a stumbling block

There is no aftermarket rear shock available for the GK71F SXR400.

So I planned to use the GK73A GSXR400 rear swingarm and shock, however, to do this I will need to remove the original lower shock linkage from the frame, and re-weld them underneath the frame to allow the geometry to work out to fit the shock absorber in.

However, the ACU handbook for production based racing is that any suspension can be used so long as the original mounting is the same.

Does this apply to F400? Also, does this mean that standard yokes have to be used also?

[AFM327]

While you may not find a production unit I'm sure something can be put together for you. I'd bet one of the suspension places that caters to racers could do it. I'm in the US but I know penkse shocks are modular, maybe maxton or the like.

[phildawson8270]

Unfortunately, both Maxton and Nitron have no interest in making a custom shock for the bike.

The standard shock is short, so getting something from another model requires a new shock linkage and associated brackets

[AFM327]

I'm not familiar with the SXR400. What is the length of the shock?

[mick41zxr]

Post a pic of shock. Both R1 & CBR600 run a shorter shock. Most decent tuners can spring & valve to suit. If you pick up a cheap ohlins the shock ends are replaceable.