Sputtering in the Streets

[TheNevadaKid]

Hi Guzzi Fam,

I'm new to the forum so let me give you a brief on who I am.

27 year old new motorcyclist riding a 2007 Moto Guzzi Nevada 750 Classic.

Third owner of the motorcycle and haven't had any problems with it other than the EFI light coming on every now and then (previous owner told me he had it checked out and there weren't any issues)

I purchased in Virginia and rode all the way to New York City in June, haven't had any issues until now.

Now that we got that in the way I am in need of assistance from my fellow Guzzi riders.

I started the motorcycle up with no issues the other day and was riding it in the city. When I got about 4 blocks I started to feel the "sputtering" sensation when higher than 2,000rpm. When I got below 1,500rpm the engine cut off on me as if I was stalling out. I attempted to start the bike again and it started but then cut off again. So I attempted one more time while revving the throttle and it started running over 2000rpm (and would stay running if I kept the rpms at a high enough number), but would cut off again if it got below 1,500rpm.

I've been told to check the spark plug and maybe the fuel filter. But was hoping I could get some guidance from some experts who have been riding for a while.


Signed,
The Nevada Kid

[Tkelly]

Might be throttle position sensor.

[fotoguzzi]

Does it have an electric peacock shutoff and is it working?
Not the exact symptoms but do you hear a whoosh when you open the fuel cap?

[TheNevadaKid]

Does it have an electric peacock shutoff and is it working?
Not the exact symptoms but do you hear a whoosh when you open the fuel cap?

I'm not aware of an electric peacock shutoff and the guy who sold it to me never mentioned it (and he mentioned everything about it before selling)

No whoosh when opening the fuel cap. My guess is that it's something to do with the Fuel Injection not giving it enough, someone mentioned it might be the throttle sensor

[LowRyter]

I think electric "petcock" was implied there.   But I'd think if you weren't getting fuel that it would be pronounced at higher speeds as well. 

I have no easy answer.  Usually it's an ignition issue and a TPS might be the culprit. 

I suppose the easy thing would be to change out the plugs.  They could be old or fouled and cause a low rpm stumble. Usually bad plug wires cause a high rpm skip, but you could still check the connectors.  Another cheap trick is some gas treatment, like Seafoam in case something is clogged and might give a part throttle stumble.

Since I don't own a 750 I don't know of the known issues with this model.  And I am considered the least mechanically inclined person here.

[guzzisteve]

The Nevada's have had issues with the lines coming off filter and lines off of in tank pump. If stock half plastic filter replace w/metal one. Other than that it is a V7 Classic with different metal & seat.

[fotoguzzi]

I think electric "petcock" was implied there. 

oops, I forgot to check my spell checker.

[malik]

Welcome, Kid, to the forum. It's heartening to see such good taste among younger generations.

Do note that the Nevada (injected versions like yours) the 750 Breva, and the early V7's (the Classic, Cafe Classic & the first Racer) are the same bike with different clothing - advice for one, works for the others. There is another forum for 750 smallblock advice and resources on Moto-Guzzi-750@groups.io that you might find useful as well.

Your symptoms sound very familiar, I'll have a stab at it now from memory, then go back & check the notes I keep in the logbook. The intermittent EFI light shouldn't be happening, but I believe it is unlikely to be related (although possible) to your main problem. To try fixing it though, best to start at the beginning - check the battery charge with a multimeter, remove the battery, clean and polish the battery terminals with a fine file or wet n dry & coat with a smear of vaseline. Do the same for each of the lugs attached to the terminals, the main earth ( at the end of the thick wire attached to the negative terminal & likely the other end attached to the bell housing). Give the same treatment to the blades of the fuses and the relays, with a little contact cleaner  sprayed in their bases. Bad connections can have all sorts of undesired effects.

Your bike does not have petcocks, electric or manual. Fuel is pumped from the pump inside the tank, down the fuel lines to the injectors. If one of the hoses in the pump assembly has come off, there would be no fuel flow at all. It's possible that the fuel filter attached to the pump inside is blocked, or distorted (from ethanol) - a not uncommon problem - but this doesn't seem to match your symptoms.

With your spluttering & unstable idle, I'd guess that your plugs are now soothed up - black not brownish & dry. see what happens if you replace with new ones - BR8ES. Switch your multimeter to ohms & check the resistance of the caps & HT lines - should be 5 ohms both sides. A crack in a spark plug caps can encourage bad running, swap them out with new ones - LB05F - checking that the copper of the HT wires is bright & clean. The ensure that you could clip the ends off before screwing in the caps. If there is a problem with the coils, it should show up with dissimilar readings on the ohmmeter now.

The 2 throttle body bikes like yours can be sensitive to blocked air filters. Take yours out (yes, I know it's an awkward pain)  and check it, replace it if it's dirty or it's not an OEM one - the OEM ones are the best, do not bother with substitutes. Wipe the inside of the airbox with paper towels - it should be clean and dry in there. Be sure the align the filter in the rails for it - it is easy to get it skewif.

I'd say it's unlikely to be the TPS (throttle position sensor - that little black round thing attached to the RH throttle bidy with 2 screws & with 3 wires coming out the end). It is not unknown for the TPS to develop a flat spot, but the symptoms for that is blips in the fuel at the rev range where the flat spot has developed. Contact cleaner in the connector can not hurt.

Check that wires coming from the oxygen sensor (that's the sensor sticking out of the crossover/colostemy bag between the header pipes) are all sound & the insulation undamaged. Ensure its connector is also clean.

Check that there's no leaks in the exhaust system. To check that the rubber manifolds are airtight, spray some Start Ya Bastard around each of the rubber manifolds while the bike is idling - if the idle changes, there's a leak.

That should be enough to be going on with. Check back with results. Welcome to the world of chasing down bad running problems. Don't let it get you down, ensure you have your libation of choice handy for the times when frustatration interferes. Hey, it's a Guzzi. Have fun.

[Guzikid]

  I'm thinking maybe water in the gas/tank...........The Kid

[Ncdan]

I don’t want to speculate because I’ve never owned a small block but I’ll venture out with this question as it’s not been mentioned yet. Can the small blocks, like the big blocks of this year not be hooked to the computer and checked for  a possible Diagnostic error code with guzzidiag?

[moto]

Since onset of the symptom was sudden, the problem would not be a gradually-developing impairment like a clogged filter. It seems likely to be electrical. If both cylinders are cutting out, the problem is not in a single coil, ignition wire, or spark plug. On the other hand, the simultaneous occurrence of failures in these components of both secondary ignition circuits is improbable.

So I am led to think the problem is upstream of the separate ignition circuits for the two cylinders and is associated with the electronic ignition module (of which I know nothing, in the case of the Nevada), or the ECU if one drives the ignition.

One thing to check for would be a bad ground that is affecting the electronics. This seems to be the most likely answer. Also check the seating of all fuses.

Moto

[GeorgiaGuzzi]

What you are describing are the symptoms I’ve experienced on several different bike when I’ve gotten bad fuel. I usually drain out bad fuel, put in known good non ethanol fuel, and a dash of seafoam to clean injectors/carbs.

[greer]

Hi there NevadaKid, welcome to the forum.  I'm thinking I recognize this bike, I believe it belonged to Ed.  Have you filled up with fuel recently?  Bad fuel would be the simplest to address.  And a loose battery cable can cause an EFI bike to go completely wonky.  Good luck and keep us posted; as you can see, the folks here stand ready to help.

Sarah

[SIR REAL ED]

Thanks to all for giving "the Nevada Kid" excellent guidance.  Tyler is a great kid and very appreciative of and respectful of age accumulated wisdom (?, or so we all think!). 

Sarah wins the "atta girl hug" prize from me for recognizing the bike and it's somewhat mentally handicapped previous owner.

Background:
-  half plastic/half metal fuel filter was replaced with new all metal filter.
-  spark plugs cap are new, as are spark plugs (new as in about 400 trouble free miles on them).
-  air filter is new.
-  in tank fuel line is new and high quality (about $27 a foot IIRC).

right now, in light of everything I know about the bike and Tyler (see above) I am leaning towards bad gas/water in the gas.

I have advised Tyler to fill the tank with non-ethanol gas, and add some "dry gas" (Isopropyl alcohol).  In these weird times, especially near NYC, (I would not be surprised if "commuter traffic" is down 90% in that area) and the gas in the in-ground tanks is much older than normal and has absorbed a lot more water than normal.

Tyler has a lot of sense and is not afraid to ask for help.  As I have told him, often the simple things are the problem.  Never hurts to replace spark plugs, right?

As I was told many years ago "That's the problem with kids these days!  You teach them everything you know, and they still don't know anything!"

Anybody in the NYC area know of any good Guzzi shops or mechanics in case it proves to be something more complex?

Thanks again to all for helping out a fine young man!

[SIR REAL ED]

Hey Tyler,

After adding some fresh gas and dry gas, if that does not solve the problem take off the gas cap and try running it again.  This can all be done stationary.  No reason to try riding the bike with no gas cap.

The gas cap vent on my DR 650 was recently clogged.  Since the petcock recently went bad, I "wrongly" assumed bits of petcock gasket clogged the fuel filter.  After a few stall outs, waiting a couple minutes and restart, I realized it might be the gas cap vent vapor locking the gas tank.  Sure enough pulling off the vent line fixed it all.

Other option is now that the bike has been transplanted from Virginia to New York, if might be suffering some cultural shock displacement syndrome.  You might need to teach it some Yankee swear words.

 

[Chuck in Indiana]

What you are describing are the symptoms I’ve experienced on several different bike when I’ve gotten bad fuel. I usually drain out bad fuel, put in known good non ethanol fuel, and a dash of seafoam to clean injectors/carbs.

(and would stay running if I kept the rpms at a high enough number), but would cut off again if it got below 1,500rpm.

I'm in this camp, too. I was coming home from Florida one time with the Centauro and had exactly those symptoms. Wouldn't idle at all. Ran ok at higher rpm, so I just continued on. After the next fuel stop, it cleared up.

[Zoom Zoom]

The fuel line separated on Jan's Nevada coming home from the New York rally one year. We lucked out since we were not far from the KOA.

If, as some postulated, the filter has split, there could be enough fuel to prime the injectors but not enough to keep it running.

If you have a small camera on a flexible stem, or a friend who has one, you can take a look in the fuel tank and look for the trouble.

Now with regard to a clogged filter. I generally agree with what was already suggested, but I personally encountered the filter on my bike seemingly working without trouble until the next time I went to use the bike. It ran fine when I parked it and a week later it would not start. That turned out to be a clogged filter. I will note that this goes against logic and I have dealt with GM's better idea of a filter stone in the fuel inlet of their old carbs years ago. Those failures were as I would have expected. In the case of my EV, I really didn't expect this to be the trouble.

Just sayin'.

John Henry