It just dawned on me while reading the Haynes fzr600 manual I got off eBay that me 400 has 600 carbies on it.
Question is, can the 600 carbies be jetted properly to run on the 400? or should I be looking for 400 ones which are very rare in Australia.

You can use 600 carbs, you can swap the jets from your originals.

Evilchicken0 wrote:You can use 600 carbs, you can swap the jets from your originals.

Hi Evil,
Thats a problem because I dont have the original carbies.
The carbies that came with the bike are the BDST32 which I understand are found on the fzr600,sp and Japanese imports.

On the Factory Pro web site they say the needle jet (emulsion tubes) for the 400 are 30.38mm in length and the 600 are
35.31mm. I have the 35.31mm one in my carbi. This is what makes me think I have the 600 carbies.

So I cant change the needle jet or matching needle. Also the main air jet is not removable and on the 600 is #65 where as the 400 is #60. I dont know if the difference in the main air jet would matter that much or should it be matched to the main jet?

I have also found in some of the different fzr400 manuals two sizes of main jet, and needle are used. I think this is because
the two outside cylinders run cooler than the two inside ones.

I really need a starting position with regards to what size jets I should buy taking into consideration I have a standard airbox and filter with a loud after market pipe. ITs all a bit to confusing for my litle brain.

I didn't know the SP carbs were different ... but I doubt they'll be much difference in reality.

You have a 3en1 Exup engine so it's a Japanese import. The SP vesion is a 2TK and uses the same exhaust and airbox, the only real difference in the engines is a lighter valve train in the SP engine (the othe changes are in transmition). You pipe probably won't affect the mixture that much, you might need to change the needle position.

Your best bet is to get it dyno'd and look at the air / fuel mixture and ask the guy what he thinks it means .... don't worry about the power figures that much all you really want is a smooth curve.

The different jet sizes are as you thought, to deal with heat.