2002 426 black smoke with sudden throttle movement

11 replies to this topic
  • freestyler727

Posted May 13, 2002 - 05:24 PM


tried to change pilot from 140 to142 to 145. always the same symptom. turned air screw in & out.put bike in gear it haslike atiny hesitation wiyh black smoke. any suggestions thanks larry

  • John_Lorenz

Posted May 14, 2002 - 01:50 AM


Make sure you did not over fill oil

  • thumper4life

Posted May 14, 2002 - 02:28 AM


is it cold?

  • John_Lorenz

Posted May 14, 2002 - 02:39 AM


Let me check

  • John_Lorenz

Posted May 14, 2002 - 02:40 AM



What was the question :)
sorry could not resist Been at work since 1am damn enga-nears

  • thumper4life

Posted May 14, 2002 - 02:51 AM


lol :)

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  • vznx1w

Posted May 14, 2002 - 03:47 AM



Black smoke is an indication of over rich fuel mixture--blue smoke is caused by oil in the combustion chamber.

It sounds like your black smoke occurs during rapid throttle movements (due to your description of "hesitation"). I suggest that your accelerator pump is over-active and recommend that you perform the "BK Mod" (well documented in TT) to limit accel pump stroke.


  • Mark_Cantrell

Posted May 14, 2002 - 04:01 AM


Yeah, FreeStyler,

We need some more information. Black smoke (make sure it's not blue or smell like burnt oil) is an indication of so much fuel that there isn't enough air to burn it all leaving soot.

The problem I have is that you were going richer. What made you think you needed a bigger pilot to begin with? Not being smart, just asking. Is there some other symptom you're working on?

Next is when does the black smoke come on? If it is idling in neutral does it happen? Does it change if you shift into gear, that is does the smoke change? Now most important, if you blip the throttle from closed to less than 1/4 throttle does it smoke. If you blip it to 1/2 throttle does it smoke. If you whack it to wide open does it smoke. And finally, if you get smoke at a throttle position and hold it, does it continue to smoke. You could be rich somewhere besides the pilot or have an overactive AP.

Oh yeah, have you run it long enough to burn out anything that was built up in the cylinder and exhaust?

Good luck,

  • Hick

Posted May 14, 2002 - 07:23 AM


Originally posted by freestyler727:
tried to change pilot from 140 to142 to 145. always the same symptom. turned air screw in & out.put bike in gear it haslike atiny hesitation wiyh black smoke. any suggestions thanks larry

Some thoughts, Dude:

Your bike doesn't have an air screw.
Being in CO, you probably don't need a richer pilot.
Stock pilot is 42, not 140, so, like, you are tripping me out with your post, bro!

  • Shawn_Mc

Posted May 14, 2002 - 07:40 AM


Freestylers with wrenches=scary!

Freestyler, your bike is on the verge of flooding. Your richening the pilot is making the problem worse. Go back to the stock pilot, and do the BK mod as suggested earlier in the thread. The bog is coming from too much fuel, not, a lack of fuel.

  • freestyler727

Posted May 14, 2002 - 04:08 PM


your right its a42 pilot jet . i cleaned the pilot air jet & main air jet claened carb completely. also cleaned air filter.150 main 42 pilot 1 3/4 air screw. waiting for filter to dry.it smokes cloesed to 1/4 trottle when in gear. no smoke any other time runs good mid &top thanks larry

  • Mark_Cantrell

Posted May 14, 2002 - 06:34 PM


Your pilot is too big. Most carbs have an air screw to fine tune the pilot circuit. This carb has a fuel screw, no air screw unless you buy one from Sudco and they aren't adjustable without removing carb. The fuel screw is in (CW) from less gas and out (CCW) for more gas. Don't turn out more than 2 1/2 turns or you risk it falling out.

If a 150 main jet is OK for your altitude, and it's probably too lean, you should be looking at a 35 or 38 pilot. If your plug isn't fouled by
now, it will be soon.

One last thing. Is there a difference in smoking in neutral and in gear with the clutch in? Your last post indicated it only happened in gear. What about in gear but sitting still. If a difference between neutral and in gear clutch disengaged, use a search for the blue wire mod.

Good luck,

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