anyone seen one of these bikes, i have seen a bike with a er6 engine fitted into a fzr frame its throwing out 90+bhp and handles like a dream!

The ER6 handles very well anyway and there's a Kwak banana swingarm from the Versa's that fit's the frame.
Not sure they'd be much weight advantage using the 400 frame over the Kwak's

Roy Richardson won the Sothern 100 on one of these, and Dan Kneen came 2nd at the ulster. I have a RRSP with motrac tuned engine but am toying with the idea of sticking in an er6 engine as you can pick them up for £500-£700.
I have seen a company that can get 98bhp out of the er6. Not that I would go that far. Problem for racing is that the new 650twins standard are putting out 75bhp. So unless the rules change the 400's are dying a death at club racing.

Tim Blakemore's dyno run on my Thundercat engined 1wg 2tk showed 102hp

Untouched engine, K+N, Scorpion racepipe

Ah but that puts you with the 600's and the new bikes are running 130bhp and look at the moto gp 2 bikes 140bhp.
Just take a look at this years Manx GP I think there are only 4-5 400's and the rest are all 650's.

The lap record was held by a ThunderCat engined 3TJ for some years