Can standard or flatside carbs off other bikes be fitted to the FZR?
Obviously if the choke is massively bigger than standard its not going to work til its sucking a lot of air - but there must be alternatives out there that arent a million miles away?

The standard cv carbs are OK, the laterSP versions used flatslides (33mm I think). I guess the later foxeye 600 would fit. You could use others but you'd need to mod the spacings to fit the cylinder centers

I was really thinking of flatslide upgrades - maybe something off another 400 (zxr? cbr? gsxr?) or even a 600 ?

Don't think 600s had them ... maybe another 400 but don't know which