Original owner finds a *sputter*

[po18guy]

2 hours ago, docc said:

Yep, that is low fuel on an early Sport (chin-pad, external pump/filter) tank.  The right "lobe" holds up to 0.8 US gallons of "fuel." Or is it half (or more) of accumulated detritus, water, and "binary azeotropes?"

Draining the fuel from the regulator return hose will only drain the left side "lobe."  The right side lobe will have to be siphoned from the filler at the top, or the regulator removed, or the tank removed and turned on its head.

Fully draining your tank should be properly shielded from the public eye . . .

@czakky knows how I wait for these moments . . .

My 1966 305cc YM1 has a crossover hose connecting the tank "halves." Oh, those inscrutable Japanese!

[Bbennett]

9 hours ago, Cabernet said:

What year is the V11? I understand the last ones had tanks with integral pumps. I had similar symptoms with my Nevada ie. Was a split hose causing reduced pressure to the injectors. The escaping fuel leaking back into the tank. The fill up increased the pressure just enough to hide the symptoms for a while, but ran pretty lean bluing  the can and eventually failed completely.

It is a 2001 model

[Chuck]

I think you are on the right track by draining the tank and getting *all* the water out of it. Of course, that may not be it, but..

(settling in to camp chair around the fire)

Let me tell you a story. One time a guy asked me what was wrong with his Luscombe. His little 65 horsepower Continental would purr along.. hiccup.. then continue purring. He said he was getting afraid to fly it. I said, "You didn't drain the carb at the annual inspection like you are supposed to, did you?" "Uhh, no." We did that, and he lived happily ever after.

Water is funny stuff.

[Gmc28]

I think you are on the right track by draining the tank and getting *all* the water out of it. Of course, that may not be it, but..
(settling in to camp chair around the fire)
Let me tell you a story. One time a guy asked me what was wrong with his Luscombe. His little 65 horsepower Continental would purr along.. hiccup.. then continue purring. He said he was getting afraid to fly it. I said, "You didn't drain the carb at the annual inspection like you are supposed to, did you?" "Uhh, no." We did that, and he lived happily ever after.
Water is funny stuff.

+1
Took a friends 140 for a spin yrs ago to exercise it, not realizing in my youth that a sump drain located mid tank won’t be the low point when a tail dragger is on the ground (my t-craft didn’t have that issue). Ran perfectly sweet till leveling out at 800’, then my very young son asked why the plane was so quiet...
After paying an unscheduled visit to the farm of my in-laws on one of their fallow fields, the water was removed by raising tail, then flew it back.
Water trapped in the wrong spot is “undesirable”.
Drain water, then add some fuel additive, and done. If that’s the issue here.

[Scud]

1 hour ago, Gmc28 said:

After paying an unscheduled visit to the farm of my in-laws on one of their fallow fields...

...and that, ladies and gentlemen, is why aircraft maintenance is even more important than motorcycle maintenance. 

[MartyNZ]

If you find water, you should change the fuel filter, and clear the screen on the fuel tap inlet. I had brown fuzz through my bike fuel system that may have come from disintegrating filter paper.

[Cabernet]

Did this issue get resolved? What was yhe cause?

[hammershaug]

*bump*

[Bbennett]

Update: I am the original poster.  I used a clear siphon to drain (most of) the fuel tank and the fuel flowed out with a beautiful blue color with no visible impurities.  This emptied approximately 3.8 gallons.  My plan to then carefully examine the "dregs" of the tank was ruined when I failed to correctly turn off the fuel petcock and spilt the remaining pint or so of gas on my (cold) engine and onto the floor of my garage. I removed the tank at that point and emptied out the final drops of fuel.   

The fuel spill prompted me to clean the engine, which I have not done in some time. 

I then reinstalled the tank and added a pint or so of new fuel taken from my Honda (which has a higher gas tank) and the Guzzi fired up nicely [as is usually the case].  I only added a pint so that I was definitely using the bottom part of tank (tank was emptied so this was a moot point unless there was something really gummy in the hidden crevices).

I have yet the take the bike out for a proper spin as I had to deal with the garage floor and smell of fuel.  That is the real test and I will report back later.

 

 

[docc]

42 minutes ago, Bbennett said:

Update: I am the original poster.

I then reinstalled the tank and added a pint or so of new fuel taken from my Honda (which has a higher gas tank) and the Guzzi fired up nicely [as is usually the case].  I only added a pint so that I was definitely using the bottom part of tank (tank was emptied so this was a moot point unless there was something really gummy in the hidden crevices).

I have yet the take the bike out for a proper spin as I had to deal with the garage floor and smell of fuel.  That is the real test and I will report back later.

 

 

For myself, I don't think I've ever had a moot pint. 

[docc]

On 6/14/2021 at 11:28 AM, Bbennett said:

Took V11 sport out for a long drive yesterday (this bike is single owner and is used alot and runs quite well in the mountains) and the bike began to have particularly bad flat spot around 2800rpm which I attributed to the warm temps and city driving as I re-entered town.  Then it got really bad ......lots of coughing.  Fuel light flickered.  Backfire.  Time for a fill-up.  With new gas she was happy. 

So let me think about this.  The tank was not empty by a long shot and now I have a new theory that I have some very nasty old gas and crud in the bottom of each fuel tank "lobe."

It occurs to me to ask @Bbennett: original, early electric petcock? Not yet converted to a manual petcock?

[Bbennett]

18 hours ago, docc said:

It occurs to me to ask @Bbennett: original, early electric petcock? Not yet converted to a manual petcock?

I actually cannot tell with certainty whether it was switched out-- and if it was it was almost 20 years ago .  I observe that both sides of tank have an apparatus connected to fuel lines and each are turned on/off by rotation in plane of the garage floor.  One is controlled by a knurled knob and the one on the right is rotated as like a rudder stick.  So that sounds like a manual petcock has been added.  Still, on left side I do see a (possibly vestigal) pump-like shaft with elec wires coming out of the bottom. 

[Bbennett]

OK, after replacing the fuel I did a test ride today and the sputter is not fixed. 

Symptoms:  The bike will start fine.  It will run OK for about 30 seconds after which there is a gurgling (underwater sound) sputter / misfire that occurs first at 2000 RPM and then seconds later at 1500 RPM and finally the bike if left to idle will die after about 3 seconds.  This does not require load - is repeatable in neutral.  Bike will start and show same symptoms (idles fine at 1st etc.) after 5 minutes rest.
 

Bike history: Always been a strong runner, has approx 60K miles and is ridden at least every 2 weeks.  Bike has always had a weak elec system, I have replaced regulator 3-4X over 20 year period.  Bike suffers from a parasitic elec leak, I have to put it on charger before a ride if it has not been ridden the day before.   This has resulted in long periods of the bike being on a charger.  Bike has always had a rough spot at 2800 RPM - never could fix it.  The 2800 stutter is exacerbated by hot weather but I can typically throttle "thru it."  Minor note: Temp shielding on fuel lines to avoid fuel boil has had no effect on temp stutter.

What I have checked / recently touched:

a. Bike exhibited the sputter for 1st time week ago when Reserve Light was indicating low fuel level.  This was at 60 MPH / 4K RPM.
b. Adding fuel allowed bike to get home fine (approx 3 miles).
c. 3 days ago fuel tank drained*, new fuel (from working Honda bike) added.  I was careful to get fuel into both lobes of tank - me not being sure which side sucks the fuel. Still, the fuel tank is not full.  I would estimate there is only 3/4 of a gallon in the bike.
d. *When tank was drained it was removed.  Upon installation of the tank I turned the rod on right side all the way counterclockwise (see pic).  The knob on the left is fully turned clockwise.  ***Is this correct?***  Elec connectors were mated under tank as per usual. 
e. Bike started fine after fuel tank installation w/ pint of fuel.  Fuel reserve light was not lit (but it is unreliable). 
f. With 3 addit. quarts of fuel added, a test drive --in warm but not hot hot weather --showed symptoms above.  This stutter is far worse than the temperature stutter noted in history section.  LED showing battery level showed the battery was near fully charged during test.
g. 6 months ago I replaced main battery cable with new, super conducting 3rd party cable.  Prob has 500 miles on it - no issues.  Fuse on new cable is intact.
h. Main Guzzi fuse box today revealed a burnt 30 amp fuse.  I replaced the fuse but symptoms continued.  A 20 amp fuse was replaced with the correct 15 amp fuse.  No effect.
i. One of the battery terminal screws was not fully tight.  When tightened, symptoms remained.
j. Spark plugs changed 100 miles ago.  Spark plug wires have not been replaced for over a dozen years.
k. No change in exhaust smoke noted (exhaust not visible).

<pics below>

Thanks for your advice

Bob

 

p.s. Air filters removed for pix

 

 

 

 

 

[docc]

" c. 3 days ago fuel tank drained*, new fuel (from working Honda bike) added.  I was careful to get fuel into both lobes of tank - me not being sure which side sucks the fuel. Still, the fuel tank is not full.  I would estimate there is only 3/4 of a gallon in the bike.
d. *When tank was drained it was removed.  Upon installation of the tank I turned the rod on right side all the way counterclockwise (see pic).  The knob on the left is fully turned clockwise.  ***Is this correct?***  Elec connectors were mated under tank as per usual. "

Regarding your "c", above, my testing indicates the right lobe will trap 3/4 US gallon of fuel in the right "lobe." Perhaps you will benefit from adding another full gallon of fuel.

Regarding "d":

  1)  Fuel is tapped from the left lobe through the petcock. Your manual petcock is visible in your first picture and the knurled knob on its bottom should be turned fully on (counterclockwise looking up at it from below). Make sure your left side petcock fully open  (counterclockwise). These directions are as if you are looking up at the petcock, so the arrow direction in your image looks correct, but worth verifying.

  2) I am having trouble understanding what you mean by "the rod on the right side."  What is pictured in your second image is the regulator with the fuel line that returns unused fuel to the right (trap) lobe and should not be turned. Can you clarify what you turned on the right side?

[Scud]

I have a new theory for you, based on my experience with a Greenie. FWIW, I bought it for cheap, because the PO gave up on getting it to run. It had symptoms similar as you describe, and eventually.... I found it.

The fuel lines had started to decompose from the inside, most importantly, the main line from petcock to pump. Bits of rubber had partially blocked the inlet to the pump. Sort of like having a slow drain in the bathroom sink, which drains eventually, but not as fast as it should. In my Greenie's case, it would sputter at about 2500 RPM because the pump couldn't push the fuel through fast enough. New fuel lines... bam, perfect runner. 

I have heard that decomposing fuel lines can also create internal flaps that will act like valves to restrict fluid flow. Not seen that myself, but worth considering.

Bottom line... if you have never done so, consider replacing all the rubber fuel lines.