Stock hp on a z400 is around 27 and around 34 on a 450r. Can't remember the site but they where showing the power there pipes added and had the stock hp for most machines to

 

Found the site HERE

 

the z400 will never compare dirt wheels did a test with the yoshi z450 and a piped yfz and the yfz took it every time thats pretty sad because the yoshi z450 is a fully built race motor.

 

Well now I guess I should apologize for bustin on your 03 lol ok no more z on z crimes. I'm actually surprised that those are rwhp numbers. As for the hmf numbers, I didn't get those from hmf. I saw those numbers on a dealers auction listing on ebay. I went back and looked for them. When I find them I'll save the links and post them. They probably are bs being that high. The reason I assumed they were off the crank is because they're so high. I believe the accepted figure for frictional loss through the drivetrain is 20%. So if those numbers are true, then that would be a 11.4 gain with full system. As someone else stated, it's probably an accross the board gain added up. Either way my point was that adding a pipe does add significant power gains.
I have a z and I don't think as an average Joe you could mod enough to hang with another average Joe on a 450r on a track or drag. It would be easier to do on a trail because you can only go so fast. I stick with my brother on his yfz through certain portions of the trails, then on faster parts he loses me. Although I've never actually riden with a 450r from what I hear they have more low end grunt than the yfz. This would make them faster in the trails, but with the insane top end of the yfz I believe it would probably win over the trx unless it's a realitively short drag. This is just my opinion based on what I've heard from people who have riden both or one or the other. I've riden the yfz and it's crazy. I wouldn't want it for the trails. My brother and a friend with one love them, but they geared them way down. I still prefer my z, especially for the reverse. I laughed my @ss of at my brother every time he had to get off to turn around or in the really tight spots where he had to keep getting on and off to do a 5 point turn.
Anyways, it is apples and oranges with trx/z. With trx/yfz it's more apples to apples. But I prefer oranges.

 

just got back from a 4 day trip to pismo. my buddy has 2 z400's and i wooped em all weekend with my 450. theres no match.

 

i agree with you, i have both bikes as well.

 

Okay here's the one for slip on that says 9 hp

 

....and here's the one that say's 12 hp The blue one I was looking at before said 13 but either way I know these numbers must be exagerated

 

Dont believe it just because its in someones ebay advertisement. There is no way in hell that you will get 9hp out of a pipe on a stock z400. Again, the horspower gain from just adding a pipe to a stock 400 is not that great.

 

I'll believe 9-12 hp gains over stock, but not peak gains. Take a look at what rpm these gains are... HMF doesnt even claim 12 hp peak for the raptor 660.