2005 KX450F

So far what Kawasaki has released is that the new machine's 449 cm3 DOHC 4-valve engine is housed in a semi-double cradle frame with a unique tapered box-section backbone tube. The photo's reveat that's an aluminum, non-perimeter frame - both the 450 and the 250 2-stroke will return to a "traditional" backbone style frame. A close look at the engine shows a mount that was clearly built for a perimeter frame, so it looks like Kawasaki did test that combination.

The Kawasaki makes a departure from the previous two 450s and the rest of the KX clan with a non-perimeter aluminum frame.
Check out the huge weld job at the headstay.
It's real! Tetsuy Mizoguchi demonstrates the KX450F's roost throwing abilities.
The slim profile and well tucked in are evident in this angle.