high flow header/ loss of torque?

86 xr600r. need a new header. i have heard a higher flowing pipe will reduce low end torque, is this true? fmf has one that say's it will increase low to mid power. any thoughts? tim . i have after market ex. already. wileyco.

The higher flowing exhaust will have less restriction, so you will lose the backpressure required for low and mid torque. The top end will be noticeably more powerful though. I have an FMF Q full system, and it has a portion of the midpipe that looks like a small expansion chamber. They call it the PowerBomb. I'm guessing this is the one youre talking about. I am not sure how much torque it gives, because I had my engine rebuilt (overbored) and carbs jetted at the same time I put the exhaust on. Let us know what else you find!


I put a high flow fmf header on my 650l and seemed to gain some low end grunt, am told the powerbomb header is a little better on the bottom end.

I have the powerbomb header and powercore4 (650L)- great low end and gain throughout. It's better across the board now. way more on the bottom - lug down and pulls...

good luck!


i just ordered a stock head pipe from xr's only/ceramic coating. i wanted to stick with oem size. they said a couple weeks, hope it works out.

Here is another opinion. I don't know I just found it looking for 650 stuffl

fmf power bomb

I have the hi-flow headers with FMF PC IV and thought it was too loud. The bike had tons of torque throughout, but definitely had a lot of top end. I put the FMF quiet insert (baffle basically) in there and noticed a gain in low end. I'm guessing because of the back pressure. Bike is nearly as quiet as stock now and I think it actually runs better. The jetting my have been just a tad lean as every now and then at low elevation I get popping on the decel. Now it seems right on. Who knew a baffle would actually make the bike run better.... I like to take it out every now and then (mostly around town or private property) just to let her scream, and I'll admit it even though I firmly believe in being quiet.... it sounds awesome.

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