Black, sooty exhaust

I did a search for a topic like this and I couldn't find anything; so, if you know of a subject title that would answer my question I would appreciate the reply. Otherwise, I would appreciate any comments.

Bike: '00 WR400 with WB E-Series Pro-Meg exhaust with 12 discs, re-jetted to match, airbox lid off, and YZ timed.

After my last couple of rides, I noticed the discs on the exhaust were black from the exhaust. Being an old 2-stroke rider, I paid it no mind. I decided to start it and look at the exhaust while running. The exhaust was clear until I rev'd it real quick. Every time I rev'd it hard the exhaust was a little sooty. It was enough to get a little on my hand when I put it close to the discs.

Is this a jetting issue or could this be an engine problem? It doesn't look blue -- as if burning oil. It's black and sooty.

What do you all think?



Sounds like you are a little rich. Can you throw a few more plates in to help lean it out??

It sounds a bit rich up top. I think mike was "sarcasticly" mentioning :) Was that with so many Discs in your Exhaust, you have caused the engine to "compress" the Faster moving Exhaust and cause some of the flow out of the cylinder to increase richness. At an Idle, Its not anywhere as bad. But, as you move up in RPM your bike will run progressively richer. Think of it as "constipation" And having to Squeeze really hard. :D Cant always get it all out in one shot.

You might remove a couple discs, and let her breathe a bit more.(I know, its slightly noiser) I guess White bros makes a End cap for the E series that can be adjusted with a screwdriver. It opens the end of the cap so it blows exhaust out the side and out the end, not just out the side.Thats another additional thing to consider to make the changes from More performance with just a simple adjustment.

Good luck.


This is probably a rich jetting condition. Keep in mind when you rev it hard that the accelerator pump is squirting fuel and richens the mixture temporarily. With the pump disconnected there would likely be less of the black soot and smoke.

You could lean the pilot circuit or move the needle clip to a leaner position, up to the point where a hesitation or bog results and then go back a little.

The stock needles in your '00WR and the '01 WR can make it little difficult to get this much better (DRS & DRR). These needles are lean on the straight diameter at lowest throttle, then a little rich (clip), then lean at 3/4 throttle(taper). A DVP needle should be easier to get adjusted to run clean. (search on DVP)


[This message has been edited by James Dean (edited 04-16-2001).]

Nope, I wasn't being sarcastic. On my IDS2, If I added more plates, it increased flow, decreasing back pressure. It leaned the bike out. As I removed plates it began to choke up. It was a different pipe so it may work differently.

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