<< All I wanna know is how many ponies are in a 400ex with a high compression piston. the z has is what 11.2:1? if the 400ex had this much would it have the same hp or maybe more???? >>



The general rule of thumb is 3-4% for each point of compression that you raise and engine. You can gain slightly more with a more aggressive cam. Your looking at gaining 1-2 more rwhp by bumping a 400ex up to 11.2:1.

The Z400 makes more power because it has better volumetric efficiency. Head design, intake and exhaust ports, valve shape and sizes, carb, exhaust, bore and stroke, and most importatntly valve events that are dictated by the cam all contribute to voumetric efficiency.

 

I've had a 2004 Kawasaki kfx 400, which is a z400 with law's name an plastic on it an I now have a 2002 Honda 400ex. I seriously miss my reverse on the kfx (z400) and I would rather have my kfx back....seemed quicker revving an a little bit easier to steer and ride.....if I ever get the chance to trade back to a kfx or find a decently priced used one, I definitely would do just that

 

I dont want to get into this but I agree with YZ guy. Both quads are great. They are actually very similar and both have a lot of available mods.