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Runs lumpy when warm 2007 xx


Bats62
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Hi. She starts easily with no issues and rum perfectly initially. When a bit warmer the engine starts to sound a feel lumpy as if trying stall but just picks up at the last minute.  Always been serviced changed the plugs twice to see if it helped.  Could the cold start mechanism be faulty (feels like choke sticking ) dont even know what or how to change it if needed.  Any help will be greatly appreciated     thank you in advance 

Bats 62 
 

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If the charging system is okay (good battery, etc.) and the symptoms persist, check out the fuel pressure regulator (FPR). Lift the tank, pull the vent lines, and look for raw fuel in those lines--even a trace is an indication of a compromised FPR diaphragm (a pinhole can do it). If that's the case, it'll only get worse--replace the FPR. That job is neither difficult nor too expensive.

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My first thought was FPR as mentioned, or maybe a bad O2 sensor.  I don't know how much the O2 can mess with these, but because the sensor only starts working once warmed up it made me think of that possibility.  I've had several experiences with cars where a bad O2 won't throw a code but will mess with the fueling a lot.

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As far as I know, the cold start mechanism only holds the throttle open and doesn't change fueling so I don't think it's that.  If it was sticking in the cold position I'd just expect a high idle.

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11 hours ago, superhawk996 said:

My first thought was FPR as mentioned, or maybe a bad O2 sensor.  I don't know how much the O2 can mess with these, but because the sensor only starts working once warmed up it made me think of that possibility.  I've had several experiences with cars where a bad O2 won't throw a code but will mess with the fueling a lot.

O2 doesn't do shit at idle. Cold or warm. At least not on anything made in 2007.

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11 hours ago, superhawk996 said:

As far as I know, the cold start mechanism only holds the throttle open and doesn't change fueling so I don't think it's that.  If it was sticking in the cold position I'd just expect a high idle.

Wrong again. Cold start mechanism won't do shit with the throttle.

It opens bypass circuit.

 

What rpm is engine spinning when it happens?

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Perhaps something as simple as idle speed adjusted too low, that's why I asked. 

 

 

Cold start mechanism. That thing by #3, with pushrod sticking out. You may wanna remove it and clean it very well.

 

Btw, "7" is idle speed adjustment cable.

 

 

Screenshot_20221114-071922.png

Edited by tomek
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46 minutes ago, tomek said:

O2 doesn't do shit at idle. Cold or warm. At least not on anything made in 2007.

False, it does on cars/trucks from decades ago to today, but I've never checked to see if it does on bikes.

 

44 minutes ago, tomek said:

Wrong again. Cold start mechanism won't do shit with the throttle.

It opens bypass circuit.

I was simplifying what it does by saying "throttle", there's no need to cunty.

 

 

Another possibility is the engine coolant temp sensor, if it's stuck reading low it could make the bike run rich when warm.  When they fail they usually fail so badly that it throws a fault code, but not always.  Another possibility is corrosion in the 'test connector'.  If you search "loom fix" it should show details on that.

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3 hours ago, superhawk996 said:

False, it does on cars/trucks from decades ago to today, but I've never checked to see if it does on bikes.

 

I was simplifying what it does by saying "throttle", there's no need to cunty.

 

 

Another possibility is the engine coolant temp sensor, if it's stuck reading low it could make the bike run rich when warm.  When they fail they usually fail so badly that it throws a fault code, but not always.  Another possibility is corrosion in the 'test connector'.  If you search "loom fix" it should show details on that.

Wut? This motorcycle, not car. Narrow band O2, can't control mixture at idle, because it needs to be on relatively rich side. 

 

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7 hours ago, tomek said:

Wut? This motorcycle, not car. Narrow band O2, can't control mixture at idle, because it needs to be on relatively rich side. 

 

Narrow band O2s on cars/trucks do control the idle mixture and have since WAY back.  Whether the bike's ECU uses them at idle I don't know.

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does the temperature sensor also feed information to the digital guage?  in other words, there's only 1, correct?

 

apologies to the o.p. for piggybacking...  my bird's always gotten horrible fuel mileage unless i'm riding like a granny...

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1 hour ago, ptxyz said:

does the temperature sensor also feed information to the digital guage?  in other words, there's only 1, correct?

 

apologies to the o.p. for piggybacking...  my bird's always gotten horrible fuel mileage unless i'm riding like a granny...

Hopefully, bats62 returns with an update. In the meantime, how horrible? 

 

Assume no dragging brakes, slipping clutch, silly rear sprocket, totally clogger air filter, etc.  Check the FPR for a pinhole leak. Pull the vac line where it connects to the FPR after a brief (or long) start/stop. Vac line must be DRY. 

 

Note: I think there are 2 temp sensors. One sends info to the ECU, this controls the fan.  Other does the gauge (Digital dash model).

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25-30 mpg on my regular commute, with full throttle pulls getting onto the freeway, traffic permitting.  low 40's when riding sedately in a group on the highways.  been like this for several years.

 

been awhile since i checked the fpr, which i upgraded a few years back.

 

fan comes on around at around 220 degrees.  know the part# for the ecu temp sensor?

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20 minutes ago, ptxyz said:

25-30 mpg on my regular commute, with full throttle pulls getting onto the freeway, traffic permitting.  low 40's when riding sedately in a group on the highways.  been like this for several years.

 

That is fucked.  I had to try hard to get under 40.  The only time I saw 25-ish was doing a top speed run for something like 15 minutes, then 145 for a while longer.

 

I can't remember whether the XX has an air temp sensor in the airbox too, and what that could do if it was bad.

 

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5 hours ago, ptxyz said:

25-30 mpg on my regular commute, with full throttle pulls getting onto the freeway, traffic permitting.  low 40's when riding sedately in a group on the highways.  been like this for several years.

 

 

 

 

 

 

5 hours ago, SwampNut said:

 

That is fucked.  I had to try hard to get under 40.  The only time I saw 25-ish was doing a top speed run for something like 15 minutes, then 145 for a while longer.

 

 

 

My 1997 Alaska XX (now my AZ XX) never got close to 40, 36 tops. The carbs have a jet kit in them so that may be the reason. 

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7 hours ago, ptxyz said:

25-30 mpg on my regular commute, with full throttle pulls getting onto the freeway, traffic permitting.  low 40's when riding sedately in a group on the highways.  been like this for several years.

 

been awhile since i checked the fpr, which i upgraded a few years back.

 

fan comes on around at around 220 degrees.  know the part# for the ecu temp sensor?

Have you changed you gearing?  

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8 hours ago, ptxyz said:

25-30 mpg on my regular commute, with full throttle pulls getting onto the freeway, traffic permitting.  low 40's when riding sedately in a group on the highways.  been like this for several years.

 

been awhile since i checked the fpr, which i upgraded a few years back.

 

fan comes on around at around 220 degrees.  know the part# for the ecu temp sensor?

" fpr, which i upgraded"          upgraded?

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