What did you do to get the tank to fit?

Did you cave in the bottom of the 600 tank?
run open carbs?
Different airbox?

On the 400/900 the chap cut the bottom off the 900 airbox and plastic welded it to the nc29 top.

https://sites.google.com/site/cbr400rrr ... oject-4-90

hmmmmm, I'm dubious about this as the NC23 airbox is tiny when compared to the 29 so I can see how this would work on the 900 conversion but I think this will strangle the 600 too much.

the bike is going to solely be a track bike so tank range isnt too important and I will be getting a 2nd NC23 tank shortly so may just have a go at knocking it in enough to fit over the 600 airbox.