Dark Smoke / Quit Running

[Wiley870]

I have a 2004 250SX that I've ridden twice. It always started fine until this weekend. If I get it to start at all, it will idle for 15 seconds then start spewing out dark brown smoke. At that point, the engine dies and I can't get it restarted. Same if I try and give it any gas. :bang:

I would greatly appreciate any help from the experts out there since I'm pretty new to this game.

Thank you.

 

[Jeff Gilbert]

I would suspect a crank seal

 

[sloopy]

what does the plug look like?

 

[katoom125]

I would suspect a crank seal

Or your float seat/needle leaking in the carb -- It can be just a speck of dirt. Taking it apart, pull the float bowl and lightly push up on the float with the gas on - see if it seals (quits flowing gas). I often find that I have to re-set float height on new KTM's. and always check the float shut off seat and needle for a good seal at the same time.
Sometimes if the float is set wrong you'll have gas overflo out of the carb but not always - if it's dirt and not seating properly, you more often will have gas overflo.
Just the same, your comment about dark brown smoke might be something entirely different - as crank seals and carb problems are normally accompanied by a thick white smoke as it's trying to burn oil/rich mixture.

 

[blanc]

Crank Seals........Split her open.