[jambo]

The carbs work fine, or as far as I know they're not a limiting factor. Certainly people who take engine modifications rather seriously don't seem to find a major reason to swap them out. What have you already done, and what are you hoping to achieve?

I'd have thought VTR carbs would be too wide, without doing major head work it's likely to make it run badly as there won't be enough airflow to make use of the larger diameter, and will suffer problems at lower air/engine speeds.

But that's my guess based on no practical work and a bit of rough theory.