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Author Topic: Gray smoke spit from carbs  (Read 2335 times)

AgentX

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Re: Gray smoke spit from carbs
« Reply #15 on: September 16, 2012, 10:47:32 AM »
Hm.  I went to a 25 pilot and a 95 main (stock is 25/90) and things have gotten a little better.  Yet, it's still rich. 

Spitting back has been greatly lessened but it happened, weakly, once or twice today.  Starting can now be done with the enrichener engaged, but requires some throttle to be added.  Same without the enrichener, but less throttle obviously required.

Did a plug chop at a very low speed then took the plug right out; came up with what I thought was oil on the plug and I got worried.  After a short ride around the 'hood at low speed, I waited a few minutes to pull the plug; it was sooty and insulator was very dark brown.  No sign of oil. So I am assuming that the blackish liquid I first saw was just carbon that had come straight out of the still-very-hot-engine.  Carbon residue on guns is liquidy at first, so I'll make the bold assumption it's no different from an engine.

Still, don't know why I'm so rich, but a turn or two more out on the air screw might cure that.  Or should I be looking to another cause? 

Float height is good.  I pulled the enrichening plunger from the top and cleaned it, too.  Is there anything else in the enrichening circuit which could cause it to feed extra fuel to the carb even when the choke lever is disengaged?

Just seems odd that I'm on stock pilot jetting and still rich with a K&N filter and an open header/megaphone exhaust. 

Idle is still a little lumpy but I've been able to get it smoother.  It's been a challenge adjusting the pilot mix because the beat was so uneven it was hard to tell when the bike was reacting to the mixture change instead of just another seemingly random fast or slow point.

Thanks for listening...

AgentX

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Re: Gray smoke spit from carbs
« Reply #16 on: September 16, 2012, 11:00:47 AM »
doublepostungood
« Last Edit: September 16, 2012, 12:17:45 PM by AgentX »

ace.cafe

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Re: Gray smoke spit from carbs
« Reply #17 on: September 16, 2012, 11:27:36 AM »
What is your elevation above sea level, and what are the approximate outdoor temperatures you are seeing?
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AgentX

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Re: Gray smoke spit from carbs
« Reply #18 on: September 16, 2012, 12:16:19 PM »
1800 feet AMSL, and right now it's 70s-80s (F) daytime, will drop to 60-70 in the winter and up to 115 daytime in the summer...

ace.cafe

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Re: Gray smoke spit from carbs
« Reply #19 on: September 16, 2012, 12:24:57 PM »
1800 feet AMSL, and right now it's 70s-80s (F) daytime, will drop to 60-70 in the winter and up to 115 daytime in the summer...

Well, that's high enough in elevation to make a difference in carburetion.
Try a little leaner in the pilot.
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AgentX

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Re: Gray smoke spit from carbs
« Reply #20 on: September 16, 2012, 12:32:16 PM »
Roger, copy all.  Tango, out.

Arizoni

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Re: Gray smoke spit from carbs
« Reply #21 on: September 16, 2012, 05:07:21 PM »
Before you change the jetting, you might try running the bike without the K&N filter in place.

While I'm not the type to believe in running long distances without a air filter in place, a 25-30 mile ride  shouldn't do any real harm and doing this might confirm or eliminate the filter as a part of the problem.
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jdrouin

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Re: Gray smoke spit from carbs
« Reply #22 on: September 16, 2012, 08:45:43 PM »
Also check that the little rubber grommet at the base of the enrichener shaft is attached to the brass (or whatever) base. If not, it prevents the enrichener from closeing completely and you'll run extremely rich. I was fouling plugs last year (oily or gasoline-y) before someone finally suggested the grommet and it turned out to be the culprit. I re-attached mine with silicone sealer and it hasn't given me a problem since.

Jeff

AgentX

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Re: Gray smoke spit from carbs
« Reply #23 on: September 17, 2012, 03:58:55 AM »
Also check that the little rubber grommet at the base of the enrichener shaft is attached to the brass (or whatever) base. If not, it prevents the enrichener from closeing completely and you'll run extremely rich. I was fouling plugs last year (oily or gasoline-y) before someone finally suggested the grommet and it turned out to be the culprit. I re-attached mine with silicone sealer and it hasn't given me a problem since.

Jeff

Jeff, that's interesting--I took the plunger out from the top to clean it, since I wasn't at a point where I was willing to pull the carb off for the fourth time that day.  Next time I have it off I'll take a better look inside.  Could be part or all of the problem.

Arizoni, I have run it without the filter before...not much of a difference to running it with the filter on.  But it's something I'll try again if all else fails.


Ace, I threw another turn out on the air screw on the way in today, and it ran better.  Maybe it's the altitude or maybe it's something wrong inside the carb as Jeff suggested.  Luckily the carb is pretty simple so it shouldn't be rocket science to determine it's working properly.

Thanks again, guys.
« Last Edit: September 17, 2012, 04:01:49 AM by AgentX »

ace.cafe

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Re: Gray smoke spit from carbs
« Reply #24 on: September 17, 2012, 05:25:46 AM »
If you need to turn the air bleed screw out more than 3 turns, you need to move to the next leaner pilot jet, and re-tune with that.
And on the other end of the scale, if you can turn the air bleed screw all the way in, and the bike still runs, then you need a richer pilot jet.

Those are the outer limits on pilot jets.
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jdrouin

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Re: Gray smoke spit from carbs
« Reply #25 on: September 17, 2012, 03:35:42 PM »
Next time I have it off I'll take a better look inside.

Just to be clear, I'm talking about the grommet on the *outside* of the plunger base. The plunger passes through the grommet, which is attached to a lip on the carb. You don't need to take anything apart to tell whether the grommet has come loose.

I found a picture on the web and attached it here, with the grommet circled in yellow.

Jeff

AgentX

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Re: Gray smoke spit from carbs
« Reply #26 on: September 17, 2012, 08:03:47 PM »
Thanks for the clarification, Jeff.  That rubber is fine on my carb.  Almost disappointing, because it would have accounted for a couple of things.

Ace, I'll check the jets I have.   The numbers seem somewhat arbitrary, as the sizes look pretty inconsistent.  I may have a narrower 25 jet in the box than the one I have on there now, and I'll look for the next size down.

AgentX

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Re: Gray smoke spit from carbs
« Reply #27 on: October 02, 2012, 07:41:33 AM »
Could bad ignition timing settings cause carbs to spit back?

baird4444

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Re: Gray smoke spit from carbs
« Reply #28 on: October 02, 2012, 08:19:04 AM »
check to see that your points have not closed up either by slipping their setting or wear on the rub block....
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AgentX

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Re: Gray smoke spit from carbs
« Reply #29 on: October 02, 2012, 09:22:39 AM »
The gap is good and I thought the timing had been set by ping testing, but I started hearing a little rattle going uphill at just over half throttle on my ride into work yesterday.  Just retarded it a tiny bit and we'll see how it goes tomorrow.