[adouglas]

FWIW: I had a newgen that was stock when I bought it. I put on a full exhaust, jetted it and did the other usual minor mods. When I was done it made power about like that of a stock 300.

The difference was noticeable, fun and gave the bike a lot of character, but it was not game-changing.

If it were me I'd go with the 400. The sting of the extra $$$ will fade before you know it. Speaking from the point of view of someone who went from a 250 to MUCH bigger bikes (GSXR750, track-only R6 and now a 675cc Triumph Street Triple which is my street ride), the 400 really hits the sweet spot in terms of power and weight.

The riding experience on the 300 will be what you've got now, more or less. It'll still have the performance of an economy car, which means you have to do things like plan passes well in advance and the conditions have to be right.

With the extra power, new things become possible. The GSXR was a transporter... stuck behind five slugs hogging the passing lane and a gap opens up on the right? Beam me up, Scotty. That wasn't possible on the Ninjette. Without a clear run to build up speed I just had to stay in the conga line and pass the time reading the license plate on the ass end of the SUV right in front of me.

The 400 won't be able to quite do that, but it'll certainly be more capable than the 300.