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Discussion Starter #1
so ive been trying to chase down my issue with having the bike run rough between 1,200 and 3k rpms. it only does it when it warms up. i replaced the FPR and that didnt fix anything... so i made sure i had good ground to battery and i do. next thing i checked i seen 2 vaccum lines that were disconnect from the fuel tank, i think they are for overflow lines.... the spark plugs were replaced about last year. ive ran sea foam through the tank and still and didnt make a difference. I havent ran it since the overflow tubes were put back on the fuel tank... any one have a clue as to what it could be?
 

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One of the lines is the fuel tank vent hose, the other is the overflow line (when you put in too much fuel), which connects at the filler neck. The vent hose must be unobstructed for normal operation. Check the air filter? Mice love to build houses in there.
 

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Discussion Starter #3
One of the lines is the fuel tank vent hose, the other is the overflow line (when you put in too much fuel), which connects at the filler neck. The vent hose must be unobstructed for normal operation. Check the air filter? Mice love to build houses in there.
yep i checked that as well and all is good there... i guess i could check all spark plug wires and make sure the boots are not torn
 

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Discussion Starter #4
One of the lines is the fuel tank vent hose, the other is the overflow line (when you put in too much fuel), which connects at the filler neck. The vent hose must be unobstructed for normal operation. Check the air filter? Mice love to build houses in there.
what i find weird is this started 2 years ago and last year i rode over 500 miles before it acted up again
 

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Hmm... All that soot means you're runnin rich. Too much fuel, or not enough air / spark. I'd prop the tank up and start lookin at vacuum lines. It runs OK until it warms up, you say?
 

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Back in the day, 15 people would have chimed in on this by now. Life in a ghost town...
I'll be disappointed if mcromo doesn't add to this conversation
 

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919 Rider
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Yeah definitely check your coils. I had a coil on a different bike break down after it got hot.
Might be worth checking some sensors on the bike too. Your MAP and engine temp sensor.
 

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You may already know this...
 

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Discussion Starter #11
Hmm... All that soot means you're runnin rich. Too much fuel, or not enough air / spark. I'd prop the tank up and start lookin at vacuum lines. It runs OK until it warms up, you say?
yes runs great but when it warms up it acts up between idle and 3k.. anything above that it runs awesome
 

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Discussion Starter #12
Yeah definitely check your coils. I had a coil on a different bike break down after it got hot.
Might be worth checking some sensors on the bike too. Your MAP and engine temp sensor.
where would the map and engine temp sensor be?
 

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If you haven't downloaded the service manual, you should. There's some great info in there, with pictures and everything

 
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Map sensor is on the air box and engine temp sensor is on the back of the cylinder block. These supply information to the ECU for fuel mapping.
 

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McTavish
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03whitesnake

If I have it right, the ruthless boil down is this:
It only acts up when warmed up, and between idle and 3,000. (this is crucial, please confirm or correct)
Therefore cold start and warming up condition is OK. (this is crucial, please confirm or correct)
The acting up manifests itself as running rough.
It first presented itself roughly two years ago.
It’s intermittent.
Last year you got as much as 500 miles between events.
The exhaust ends are showing soot.

First, I think this thread will be of some help re figuring it out:
Diagnostics Process

Did you do any work on the bike immediately or very recently before the first event?
If so, what was it that was done?

The following parts have since already been replaced, or proofed, and no resultant change observed :
Spark Plugs / FPR / Grounding / Hosing ( all hosing ? i.e. all vacuum lines, not just the tank lines, condition checks not just position checks - please confirm or correct)

Noted are the following good suggestions from the others so far:
MAP Sensor
ECT Sensor
Coils, high tension leads and boots.

Next, consider that the engine is fine all the time except for the odd time, or period of time, when it acts up only warmed up when in the idle to 3,000 rev band.

Next, consider that idle to 3,000 rev band is the pickiest need of accurate fueling being required.
The bike’s Throttle Bodies control that mechanically in terms of simple throttle opening, but the TB Sensor is what tells the ECM, correctly or incorrectly, what the throttle opening is, which in turn instructs the injectors how long to be open during the timed injection time.
For the TBS to be involved, it would have to only sometimes being sending incorrect outputs for a very narrow operating condition.
While the TBS should be checked, my thinking is that it doesn’t fit your scenario, and likely is not at all involved.

There are indications of richness.
That can be from excessive fueling and/or incomplete combustion.
Correct fueling is a function of the correctness of the TBS, MAPS, ECTS, IATS, and ECM instruction to the injectors, and the injector themselves.
The incomplete combustion could be from inadequate sparking at the plug, thus calling into question a long chain of directly related things before the plugs.
But the hardest job for the ignition system (of an engine like the 919) is to adequately spark at full power, so if it does that well all the time, ignition system involvement sounds unlikely to me.
Keeping in mind that “idle to 3,000 rev band is the pickiest condition of accurate fueling need”, what could screw that up intermittently that hasn’t yet been pondered about?
MAPS (Manifold Air Pressure Sensor): Be it within the sensor, and/or sensor electrical connections all the way to the ECU, and/or vacuum hose leak and/or connections.
IATS (Intake Air Temperature Sensor) Be it the sensor, and/or sensor electrical connections all the way to the ECU.
ECTS (Engine Coolant Temp Sensor) Be it the sensor, and/or sensor electrical connections all the way to the ECU.

MAPS effect on fueling is major, not minor, given that it’s the primary sensor for aggregate air mass flow sensing, the minor input being Intake Air Temperature.
IF there was intermittent bad MAPS involvement, I’d expect it to cause more trouble when starting and during the cold and warm up cycle for the idle to 3,000 RPM rev band, not when the engine is warmed up.

I think that IATS effect on fueling is minor, more of a refinement input, keeping in mind the typical range of IATemp’s a 919 is going to see.
IF there was intermittent bad IATS involvement, I’d expect it to effect all modes of operation moderately, not just one mode.

Maybe it’s intermittent bad ECTS involvement, be it the sensor, and/or sensor electrical connections all the way to the ECM. If that is the case, my guess is that the ECM would be seeing what appears to it as a cold coolant signal, and enrichens accordingly.


Hopefully this helps you at least some.
More clarifications from you would be helpful to all.
Plus any new info you uncover.
 

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919 Rider
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The sensors on my bike were getting to be around 20yrs old. I replaced them all with new, kept the old for spares. I’m not sure what the life span is on these sensors. Depends on a lot of things.
Just out of curiosity what air cleaner are you running whitesnake? I ask because I’ve read that over oiling a K&N filter can foul the Map sensor.
 

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Discussion Starter #20
03whitesnake

If I have it right, the ruthless boil down is this:
It only acts up when warmed up, and between idle and 3,000. (this is crucial, please confirm or correct)
Therefore cold start and warming up condition is OK. (this is crucial, please confirm or correct)
The acting up manifests itself as running rough.
It first presented itself roughly two years ago.
It’s intermittent.
Last year you got as much as 500 miles between events.
The exhaust ends are showing soot.

First, I think this thread will be of some help re figuring it out:
Diagnostics Process

Did you do any work on the bike immediately or very recently before the first event?
If so, what was it that was done?

The following parts have since already been replaced, or proofed, and no resultant change observed :
Spark Plugs / FPR / Grounding / Hosing ( all hosing ? i.e. all vacuum lines, not just the tank lines, condition checks not just position checks - please confirm or correct)

Noted are the following good suggestions from the others so far:
MAP Sensor
ECT Sensor
Coils, high tension leads and boots.

Next, consider that the engine is fine all the time except for the odd time, or period of time, when it acts up only warmed up when in the idle to 3,000 rev band.

Next, consider that idle to 3,000 rev band is the pickiest need of accurate fueling being required.
The bike’s Throttle Bodies control that mechanically in terms of simple throttle opening, but the TB Sensor is what tells the ECM, correctly or incorrectly, what the throttle opening is, which in turn instructs the injectors how long to be open during the timed injection time.
For the TBS to be involved, it would have to only sometimes being sending incorrect outputs for a very narrow operating condition.
While the TBS should be checked, my thinking is that it doesn’t fit your scenario, and likely is not at all involved.

There are indications of richness.
That can be from excessive fueling and/or incomplete combustion.
Correct fueling is a function of the correctness of the TBS, MAPS, ECTS, IATS, and ECM instruction to the injectors, and the injector themselves.
The incomplete combustion could be from inadequate sparking at the plug, thus calling into question a long chain of directly related things before the plugs.
But the hardest job for the ignition system (of an engine like the 919) is to adequately spark at full power, so if it does that well all the time, ignition system involvement sounds unlikely to me.
Keeping in mind that “idle to 3,000 rev band is the pickiest condition of accurate fueling need”, what could screw that up intermittently that hasn’t yet been pondered about?
MAPS (Manifold Air Pressure Sensor): Be it within the sensor, and/or sensor electrical connections all the way to the ECU, and/or vacuum hose leak and/or connections.
IATS (Intake Air Temperature Sensor) Be it the sensor, and/or sensor electrical connections all the way to the ECU.
ECTS (Engine Coolant Temp Sensor) Be it the sensor, and/or sensor electrical connections all the way to the ECU.

MAPS effect on fueling is major, not minor, given that it’s the primary sensor for aggregate air mass flow sensing, the minor input being Intake Air Temperature.
IF there was intermittent bad MAPS involvement, I’d expect it to cause more trouble when starting and during the cold and warm up cycle for the idle to 3,000 RPM rev band, not when the engine is warmed up.

I think that IATS effect on fueling is minor, more of a refinement input, keeping in mind the typical range of IATemp’s a 919 is going to see.
IF there was intermittent bad IATS involvement, I’d expect it to effect all modes of operation moderately, not just one mode.

Maybe it’s intermittent bad ECTS involvement, be it the sensor, and/or sensor electrical connections all the way to the ECM. If that is the case, my guess is that the ECM would be seeing what appears to it as a cold coolant signal, and enrichens accordingly.


Hopefully this helps you at least some.
More clarifications from you would be helpful to all.
Plus any new info you uncover.
hey thanks for your input! so when i start up the bike on a cold start and start riding while its cold it runs great. usually about 20 mins into riding is when i notice it at stop signs red lights etc when taking off from a stop. this didnt happen until i had my fork seals and spark plugs changed a few years ago... before that it ran great. my bike has 28xxx miles on it so i figured i would have the plugs changed while it was getting the fork seals and race tech springs put in. So yea cold start is fine. but very weird last year i thought it was taken care of riding over 400 miles and noticed it came back. so i changed the FPR and it didnt do anything.
 
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