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Black smoke at high RPM


Caddis

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2004 R1150RT. If I get above 6K RPM when accelerating hard, I get some black smoke out of the exhaust. It doesn't happen below 6K. It also doesn't happen, even above 6K, if I am not accelerating hard.

 

The bike sounds and feels fine, but the black smoke concerns me. It is significant enough that Eileen (riding behind me) noticed it and asked me if there was something wrong with the bike.

 

Is this normal, or is this something that I should be worried about? Any idea what might cause this?

 

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Evening Kevin

 

At 6K+ and under acceleration your fueling system has gone open loop. That means it could go a bit rich and not correct for it if an engine sensor is off a little or you have a plugged air filter.

 

How is your overall fuel economy on that bike?

 

As rule the catalytic converter would burn off a little richness therefore no black smoke visible.

 

SO, anything not stock on your bike like an aftermarket exhaust or a fuel nanny type fuel controller?

 

If all is stock then start by looking at the air filter to be sure it is clean and free flowing.

 

Look a the cat. to see if shows signs of running rich (like purple at the front pipe entry area).

 

How does it run out at top speed? Will it do over 125MPH sustained?

 

If the bike runs good and the fuel consumption is within reason and the air filter is clean it might be black from a little oil burning not fuel. Oil can sometimes look black after going through a hot converter. Is the crankcase overfilled above top of sight glass?

 

If it isn’t oil related it’s going to difficult to find the problem without looking at the engine sensors for correct output.

 

You could try a primary spark plug reading but if it only blows black on an acceleration over 6k you will need to install new primary plugs then make a full run under acceleration doing an ignition chop using the kill switch at the end of the acceleration run and coast to a stop with clutch pulled in (then let it cool for a while before pulling and reading plugs).

 

Other than looking at the air filter maybe run another tank of fuel through it to see if the black goes away just in case you got a load of gasoline with a little diesel in it,.

 

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Hi DirtRider, thanks for the reply.

 

I just replaced the air filter this fall, so unless there is something else blocking air flow, I think I'm good there.

 

I haven't checked the fuel economy lately, but on our trip to the UN last summer, I got around 58 MPG over the course of the whole trip. In more typical in-town riding, I believe I was getting around 45 MPG.

 

All of the fuel and exhaust related components are stock.

 

The pipe running into the cat is a mottled blue/purple. Does that indicates that it is running rich?

 

125 MPH sustained? My wife almost did a spit take when she saw that. I don't know - I have never had it above about 90.

 

I'm quite careful about not overfilling the oil. I don't usually let it get much above halfway in the sight glass, using the usual "oil dance" procedure.

 

I will take a look at the spark plugs when I get a chance.

 

I first noticed it doing this late last summer. So it isn't likely to be related to a bad tank of gas. I am a pretty conservative rider most of the time, and don't accelerate hard over 6K very often. In fact, whatever is causing it may well have been that way since I bought the bike a few years ago. It was only more recently that I started pushing the bike harder, with someone riding behind me who would notice the smoke.

 

If it is running a bit rich, should I be concerned, and what should I be doing to correct that?

 

Thanks.

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2004 R1150RT. If I get above 6K RPM when accelerating hard........ It is significant enough that Eileen (riding behind me)noticed....

 

So.....Eileen behind you as you accelerate above 6K? I guessing she's a bit more comfortable than last summer when you asked me to keep the speeds down? :thumbsup:

 

Russ

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125 on that bike? Downhill with a SERIOUS tailwind, full tuck, windshield all the way down, being towed by a Bugatti Veyron....

 

I loved mine, but 117 was like a brick wall. Maybe it was altitude....

 

 

 

If you are a "gentle" rider, maybe carbon buildup?

 

Guessing here.

 

 

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If you are a "gentle" rider, maybe carbon buildup?

 

Guessing here.

 

 

+2.. How often do you visit those elevated RPM's

 

Andy

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If you are a "gentle" rider, maybe carbon buildup?

 

Guessing here.

 

 

+2.. How often do you visit those elevated RPM's

 

Andy

 

+3.......my guess as well. You have to run these bikes hard from time to time in order to keep the carbon from building up on the pistons. My bike always runs its best after a weekend of tight twisty roads and high RPM's.

 

I'd take it out and ring its neck a little. I'd be willing to bet that it goes away.

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Morning Kevin

 

I just noticed the Colorado in your location.

 

 

What altitude you riding at? As I mentioned above those 1150’s go open loop at that RPM/load.

Running at higher altitudes internal combustion vehicles tend to go richer as the altitude increases so the fueling computer must compensate for that.

There is a barometric sensor (altitude compensation) built into the Motronic but I’m not real sure on it’s altitude fuel trim ability at very high altitudes. My Motronic fuel trim chart shows the altitude compensation goes well above 8,000 feet but the trim percentage is pretty flat above 5k.

 

 

The black smoke at 6K acceleration is really nothing to worry about as long as the fuel economy is in the ball park. The main concern of running super rich (black smoke) is washed cylinder walls therefore increased engine wear and engine oil dilution. If you only get the smoke at 6K+ and under acceleration there shouldn’t be much worry about either oil dilution or cylinder wash down. If you are riding at high altitudes it might even be normal.

 

With your stated fuel mileage numbers you must be a real conservative rider and you sure aren’t using excess fuel at normal riding conditions.

 

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One more thing to consider......Does it do this, regardless of the source of fuel? Not all gasolines are created equal.

....No, especially if it is diesel!

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Mrs. Caddis

 

So.....Eileen behind you as you accelerate above 6K? I guessing she's a bit more comfortable than last summer when you asked me to keep the speeds down? :thumbsup:

 

Russ

 

Yes, I am much more comfortable than last summer. That trip has a lot to do with it. (I'll have had my MC endorsement 2 years this coming May.) When Kevin takes off like that he is leaving me in the dust, but I soon catch up! :grin:

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So.....Eileen behind you as you accelerate above 6K? I guessing she's a bit more comfortable than last summer when you asked me to keep the speeds down? :thumbsup:

 

Russ

 

Hi Russ. Yeah, you could say that!

 

Actually, we still don't push the speed limits like many on this forum, but we do like a good twist of the throttle now and then...

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If you are a "gentle" rider, maybe carbon buildup?

 

Guessing here.

 

 

+2.. How often do you visit those elevated RPM's

 

Andy

 

+3.......my guess as well. You have to run these bikes hard from time to time in order to keep the carbon from building up on the pistons. My bike always runs its best after a weekend of tight twisty roads and high RPM's.

 

I'd take it out and ring its neck a little. I'd be willing to bet that it goes away.

 

Yup, I had that thought, also. I just wanted to make sure that this wasn't a more serious issue first. I don't run in the 6K+ range very often. So I will give it a good "neck wringing" the next few times out and see if it gets better.

 

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One more thing to consider......Does it do this, regardless of the source of fuel? Not all gasolines are created equal.

....No, especially if it is diesel!

 

As far as I can tell, it doesn't seem fuel source related. But I will definitely keep that in mind.

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Morning Kevin

 

I just noticed the Colorado in your location.

 

 

What altitude you riding at? As I mentioned above those 1150’s go open loop at that RPM/load.

Running at higher altitudes internal combustion vehicles tend to go richer as the altitude increases so the fueling computer must compensate for that.

There is a barometric sensor (altitude compensation) built into the Motronic but I’m not real sure on it’s altitude fuel trim ability at very high altitudes. My Motronic fuel trim chart shows the altitude compensation goes well above 8,000 feet but the trim percentage is pretty flat above 5k.

 

 

The black smoke at 6K acceleration is really nothing to worry about as long as the fuel economy is in the ball park. The main concern of running super rich (black smoke) is washed cylinder walls therefore increased engine wear and engine oil dilution. If you only get the smoke at 6K+ and under acceleration there shouldn’t be much worry about either oil dilution or cylinder wash down. If you are riding at high altitudes it might even be normal.

 

With your stated fuel mileage numbers you must be a real conservative rider and you sure aren’t using excess fuel at normal riding conditions.

 

The altitude around here is generally around 5500 ft., and it doesn't require a trip into the mountains for it to happen. It's good to know that this doesn't sound like something to be too worried about, so I will see if I can "clean it out" by giving it a good workout. Sounds like fun!

 

Thanks to all for the feedback.

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ShovelStrokeEd

Take it up over the pass to Grand Junction, beating the cojones off it all the way. Do the same on the way back.

 

Betcha the smoke will be all gone by then.

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125 on that bike? Downhill with a SERIOUS tailwind, full tuck, windshield all the way down, being towed by a Bugatti Veyron....

 

I loved mine, but 117 was like a brick wall. Maybe it was altitude....

 

Yep informed sources told me that in multiple attempts, 118mph (GPS) has always been the level ground, ethanol fueled, top end w/ bags and tall (but retracted) Cee-Bailey in the breeze.

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I believe elevation helps top end on these bikes. My best (Repeated on a couple of occasions) is 130 (Indicated) at 7000' elevation, using regular (86 octane) fuel. Weather threatening to rain, maybe 40f. Whis was just over 6500rpm on the tach, stock windshield, with me laying on the tank. Full load, including a duffle on the passenger seat.

 

I believe that folks do not need to use high octane fuel in these bikes much above sea level. I find better starting, cold running and power on lower octane fuel. Just sayin'.

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Yep informed sources told me that in multiple attempts,

 

Oh, yes, of course that's what I meant as well, informed sources. Somebody out at Bonneville told me right before I rode home at 5 under with my hazards on.

 

:Cool:

 

 

And PhilbyTX, that RT hit nearly every state including yours. It wasn't gonna beat its top speed in any of 'em!

 

(lights the size of hubcabs, extra fuel, and a gorilla on it might have been factors)

 

 

 

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Black smoke appears to be gone now. We were out on the bikes about an hour and a half yesterday, and I kept the revs up extra high and gave the engine a good workout whenever I could. According to Eileen, the smoke issue got a bit better as time went on, but didn't go away completely.

 

Then we went out again today, and I filled up with gas before we left. No smoke when accelerating hard over 6K, like it did before. So whether it was yesterday's good engine workout, different gas, or both, the issue seems to be resolved. Thanks for the help.

 

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