FMF Powerbomb Header for a 99 YZ400F (opinions about using it)

I wanted to upgrade my stock header with a FMF Powerbomb header and I first wanted to see if anybody has it and how they like it and I also wanted to know if a jetting change would need to happen if the Header is different??

BTW....I have a older style FMF Q Muffler (just in case everybody was wondering)

I know that if you change the muffler, I may need to re-jet but is it the same when you change your header????


Patrick M.

The header shouldn't cause you to need to rejet, although it could. I have the Power Bomb on my '03, and it works very well. The concept of the header is to widen the power curve by fooling the engine into seeing the exhaust as having no fixed length. On the '03 450, which has a distinct spike in the power band with the stock exhaust, this header makes the bike pull harder sooner and flattens out the spike nicely.

If your bike already has such a power curve, with no real flat spots, or a distinct hit at some point, you may not notice much from the PB, but it's a good mod, IMO.

I used to have a 99 400 with the stock exhaust system. I decided that I was more interested in a quiet exhaust than horsepower. I put on the powerbomb and Q muffler and was surprised that I lost no power at all. It ran great with that combo and I did not have to rejet. I highly recommend the powerbomb header.

I have the older FMF Q Muffler and so I figured it would be a waste to upgrade that but i figured I would get more power out of a new PowerBomb header than upgrading my muffler.

What do you all think???

New Muffler or PowerBomb Header????

Patrick M.

I have a PB header and FMF Titanium muffler. The PB header does smooth out the hit and I can feel a difference in the low end grunt. I'm happy with it. :thumbsup:

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