Jetting for E-series S-bend

Finally got my WR running great i.e. throttle stop ground down, removed baffle and air box cover. I am still running WR timing. The jetting feels great thanks to some help from people on this board. So to sum things up the bike rips and I love it.

So what do I do but buy a White Bros. (used) E-series S-bend. I understand the number of dics effects performance and noise output. How will this effect my current jetting? Larger main jet only or will this muffler affect the whole range of throttle openings. Has anyone run this combo for some baseline settings? Any help on this matter will be greatly appreciated.


2000 Yamaha WR400F

1988 Honda NT650 Hawk

1977 Suzuki RM250B

1974 Honda XR75K1

I have the same question and have been considering this pipe also so let me know how you like it.

Why did you decide on the 'S' bend verses the megaphone?

My dealer told me the megaphone is the only way to go because it adds much more horsepower. But, I've heard on this forum that the 'S' bend adds more lowend torque and the megaphone more upper revs. And it is CERTAINLY more torque I need here in Colorado, not extra upper end.


I decided on the S-bend for pretty much the same reasons you listed - Low end torque. Most of my riding is 2nd and 3rd gear running through the trees. I was looking through an old dirt-bike magazine when I saw a White Bros ad with a dyno chart comparing the stock, S-bend and megaphone mufflers. If a person was looking at peak HP alone the megaphone was definately the muffler to go with! My opinion has been that I'll take a easy to ride and manage powerband over a high end machine. This combination is less fatiging. All of the races I ride (hare-scrambles and enduros) the determining factor in who wins or loses is fatique not H.P. However I do agree theres more of a "fun factor" with more H.P.

The other reason was I found it on E-bay at a good price! Can't resist those "bargains". :)


I have a White Brothers E-series muffler that I fitted to my 1999 wr400. It greatly improved the power throughout the whole rev range but yes it is a low end pipe. I am running 5 discs. I have a 172 main jet and a 48 pilot with the fuel screw in at 1 1/2 turns. I also have a WB White Power filter.

As I have an australian bike the power increase in replacing the pipe was massive.

Seeya Jason

Thanks guys.

I just converted to YZ timing and although power is fun, I don't think I need any more. It would be nice to gain some low end to balance it out some.

Now, you guys need to tell me how loud the 's' bend E-series is compared to the stock pipe with no baffle. I know it's tunable. I'm talking how loud with the disks for max power?


I run stock Australian jetting, YZ timing and a S-bend pipe. It is the best $500 I have ever spent. You don't want to stick with the stock Aussie pipe. Midrange has plenty of extra go and YZ timing improved my top end. I run it with 12 disks (mostly ride on private land). It is loud especially if you give it some at low revs. Less disks quietens it considerably (still not as quiet as stock though). Another good aspect of it is the compact design. It is tucked away nicely safe from too much damage. I saw a bloke with a very second-hand looking Staintune after one soft crash.

Hope this helps.

You must remeber that the standard Australian pipe is way more restrictive compared to the US pipe with the baffle out. We don't have a removable baffle, so it's new pipes all round down under.

And I have found the same specs as Jason mentioned above work best for me, I also know a lot of guy's who went from 12 discs back to 5 and thought it was a good move, for noise and bottom end.


R o d. H.

Canberra, Australia

400 Thumpers Australia

99' WR400

I have found that with YZ timing, 2 1/2 turns on fuel screw, 48 pilot, 175-180 main, 12 plates works great, a bit loud though. Tried the quiet cone insert and the db's dropped drastically, but it was like giving the low end a shot of Novocain, mid-high was pretty much unchanged (removed it by next ride). Installed the tapered head pipe and low end throttle response suffered, but all around power greatly improved. The final fix was to go to 14 plates, sounds like too many and yes loud, but with out any question this is the best power band you can get with this pipe.

Smiley Test :)

I have a '99WR US model, running E series S Bend. It gives great low end power with 6 disks and get this...stock jetting! Runs great, starts first kick every time. It really cranks up the low end, plus I can switch back to the quiet pipe in about 5 minutes if necessary since that E-series is one loud pipe.


I have a 99WR white bros head pipe, E-series (12 discs), Throttle stop trimmed, White bros A/F and WR timing. I have been fighting the jetting since I got the pipe. Try the following. Make sure you adjust the accelerator pivot arm and float level before you do anything else. Then try the following.

175-178 MJ

stock pilot

stock needle #4 clip from top

2.0 turns out on fuel screw

You may also search using Bill in NC or email me at and I'll try to help with what I've just learned.

Good luck

Bill in NC

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