What is black smoke?

[HillTopper]

On my 98 XR400, its totally stock except for 160/60 jetting, airbox removed, 3 holes drilled in spark arrestor, uni air filter.

When i rev the bike, it throws out a very light puff of black smoke. no, it doesnt fill the yard up or anything, but when i put my hand behind the exhaust and rev it, black moisture is on my hands(dont know the word for it). its really only noticable when i rev it.

Anyways, is this just a little rich? it doesnt sputter around either, i'm just a concerned owner.

 

[cr25096er]

im pretty sure black smoke is caused by too rich jetting.

 

[SFO]

My boy scout troop was named green smoke.
I would not worry about your black smoke...
If you are intending to jet it for some purpose perhaps the color of smoke would have more meaning...
Otherwise enjoy your bike without lost sleep.

 

[The^^Rock]

few idea's

Strait from Honda Service manual :)

Black Smoke
Air Cleaner Clogged - Clean/replace
Main Jet too large or loose
Choke stuck open
Fuel Level too high. Check the float level
Inlet needle off needle seat. Clean the float chamber and fuel line and replace the needle and seat if necessary

Good luck
James :)

 

[SFO]

Excellent use of the first reference source you never read.
Thanks James.