The Sept. issue of ATV Sport has a dyno (pg 40) of a stock 400EX vs Z400. The dyno was done at CT Racing, and both bikes (stock) were done on the same machine. The Z gets a not very impresive 28.5, and the EX gets 27.3. Based on my "seat of the pants evaluation", I am guessing that these are in the ballpark. They did say that just adding a slip-on exhaust ups the Z to 32, and the Z has great hop-up potential (like 50 hp!!). There is another dyno on www.off-road.com, (stock machines done by dynojet) and the results are similar as I recall (ie. not a real big difference between the two 400's). Seems like Suzuki tuned the bike kind of mild.

The HP numbers are not all that instructive from my point of view. What I want to see is the TORQUE CURVES!! The EX makes its power down at lower RPM, where the Z seems to be something of a rever and makes its power at a relatively higher RPM.