View Full Version : FMF 4.1 system?

12-22-2007, 05:44 PM
Anybody know how much of hp gain with the whole FMF system? The KTM seems to be the most expensive system compared to other atv's $800! Just want to know how well it works before spending that kind of cash.

12-22-2007, 05:54 PM
I think +- all the exhaust kits + re jetting give around 4 or 5 hp. Correct me if i'm wrong...

12-22-2007, 08:43 PM
The HMF website posts printouts of their dyno runs for the 525 so you can see the power curve for both torque and hp. I wish all pipe manufactureers would do the same. Gains are around 5 hp. I don't remember if db levels were posted, but at $800 for any exhaust system, I might do a 540 kit first at $890.

12-23-2007, 12:56 AM
Here is the dyno chart address:
I would hope fmf gains are nearly the same.


12-23-2007, 12:41 PM
Most builders I've talked to says you will not really improve upon the stock header. A slip-on will gain just as much and save a whole lot of money. I would look into the HMFs. They have always made a top notch product.

12-23-2007, 03:02 PM
Yeah ktm stock headers are very good, you won't need to change that. Slip on is the only thing to improve.

For me it would be Akrapovic. Great design and the sound much better than hmf...

12-23-2007, 03:24 PM
thanks for the advice. Sounds like I'll stick with a slip on.

12-23-2007, 08:52 PM
check out a Baldwin slip-on. they'll be out in january and i'm sure less expensive than the Akropavic which is around $700.