FI "carb farts"

[jimbemotumbo]

I felt I needed to start a new thread even though we have several that try to address the hesitation, sputtering, farting that many of us have experienced.

 

Desperately Seeking Help!

 

2000 V11S

stucchi

M4 cans

PCIII

K&N pods

skilled rider with average common sense

unskilled mechanic (apparently)

 

I have severe "carb" farts just off idle and again around 3000 rpm with minimal throttle opening. This does not occur under acceleration ... only at nearly closed throttle.

The hesitiations are significant enough to make a gentle curve into a road rash waiting to happen. I have followed all advice in these threads and tuned repeatedly according to guzziology and the forum sages. To wit:

 

Valves freshly adjusted (tried both world and raceco spec)

New TB rubbers

Smacked the TBs into place firmly

TPS set to 150 (engine off). Also tried the fancier methods espoused on this board. My settings have been exactly spot on.

Balanced the TBs with bleeds closed using adjusting wheel, then again via bleed screws with various openings from 1/2 to 1 1/2 turns out.

With PC III. Without PCIII. Changed maps. Added fuel to specific problem spots.

New plugs.

New fuel filter (installed correctly).

Petcock wires had fallen off, so I resoldered and sealed.

 

I took it to Erico in Denver, and they charged me $130 to replace the plugs and turn the air bleeds out. I had asked for a complete tps adjustment. Thanks Erico. Lotsa help there! They are more clueless than I am.

 

Nothing has helped.

Low speed operation seems better with air bleeds closed (or nealry so).

So, WTF is going on here? Bike ran great before I started "improving" the performance - and ran great for a time afterward. The slight miss at 3k has always been there, but is much worse now.

 

I'm left with only the ECU as a possible problem. Any thoughts? The bike is basically unrideable in this condition.

 

A virtual pint or two to those who help me out!

 

Thanks!

[jrt]

So, these are the other random thoughts I have-

Could it be a sensor that's going bad? You could try cleaning and/or measuring the cam sensor, the oil and air temperature sensors (where is it located, BTW?) and the air pressure sensor is in the computer so you can't get to that one. That's a lot of tracking work, I'm afraid. The air/oil temp sensors follow the same temperature/resistance profile. The air pressure sensor sounds most attractive to me if you are in Denver. Do you live in Denver and does it exhibit the same behavior at high and low altitudes?

Could it be a ground fault? That the problems occur below 3K rpm and the alternator output is pretty low below 3K rpm is purely coincidence I'll bet. But- it's worth thinking about. How's 'dem grounds? I can't remember who it was (TX or Gary Cheek) who recommended an extra grounding strap from the headlight and it's associated wiring to the frame. The same might be said for the computer...

Back to sensors, could it be a TPS potentiometer? That should be easy to check- hook it up to your ohmmeter and slooowly open the throttle. Take a few angle/resistance readings and plot them out if you're really anal-retentive. I don't think it's linear, but it should be smoothly progressive.

 

After all that, your description still sounds like an air leak or tight valves, so I'm not sure.

Good luck,

J

[bmc5733946]

I have made this suggestion before but will reiterate: whenever one encounters running problems with late model Guzzis it pays to check the spark plug caps!!!!! I obviously cannot diagnose this problem from afar and so I may be wrong. High plug cap resistance can lead to all sorts of running problems especially low speed steady state and transitional low speeds where spark performance is critical. Higher engine speeds are much more forgiving of lost spark voltage. I personally have changed dozens of these caps that showed open circuits. NGK apparently has a problem, on my own bike I have replaced the wires with Magencor wires as I got tired of checking and replacing the caps every oil change, since the replacement I have had no low speed running problems. I had lots of burps and farts before. I work for GT Motors in Lansing MI, this is not an advertisment just a way to let you know that I truly have seen this a lot in the last few years. I believe that the mixture these bikes are required to fire make this all the more troublesome. I have found bikes where I couldn't balance the throttle bodies accurately because of this. 5K ohms is correct value for these if I recall regardless most are marked on the cap. Good luck with your problem!!!!

BMC

[Guest Nogbad]

Modifications? Pah! I'm leaving mine standard.

[txrider]

I have made this suggestion before but will reiterate: whenever one encounters running problems with late model Guzzis it pays to check the spark plug caps!!!!!  I obviously cannot diagnose this problem from afar and so I may be wrong.  High plug cap resistance can lead to all sorts of running problems especially low speed steady state and transitional low speeds where spark performance is critical.  Higher engine speeds are much more forgiving of lost spark voltage. I personally have changed dozens of these caps that showed open circuits. NGK apparently has a problem, on my own bike I have replaced the wires with Magencor wires as I got tired of checking and replacing the caps every oil change, since the replacement I have had no low speed running problems.  I had lots of burps and farts before.  I work for GT Motors in Lansing MI, this is not an advertisment just a way to let you know that I truly have seen this a lot in the last few years.  I believe that the mixture these bikes are required to fire make this all the more troublesome. I have found bikes where I couldn't balance the throttle bodies accurately because of this.  5K ohms is correct value for these if I recall regardless most are marked on the cap. Good luck with your problem!!!!

BMC

57475[/snapback]

 

Will an ohm-meter resistance check of the ignition wire always show a bad cap? Or do these sometimes open up under load?

[bmc5733946]

Tx, The way I always check them is to unscrew the cap from the wire and check just the cap with dvom. The wire is solid core so while the cap is off I always nip the used part of the wire off to give the cap's internal screw stud a new bite. The caps are available from several sources, one shouldn't have to give a lot for them, five or six USD seems about right. I know it may be sacriligious to some but check Dennis Kirk or some of the other el cheapo places. I have never seen them open and not show on a dvom but I suppose its possible. The reason they affect things more at idle and slow speeds is that the engine is turning slowly enough that the firing voltage is lower because the input voltage to the coil is lower ( you know how those Guzzi's charge ) and the need is greater because at slow engine speeds the mixture is harder to light and higher engine speeds allow this to sort of go unnoticed as the flywheel keeps the engine spinning and also damps some of the vibration that would be more noticable at slower speeds. I know I'm not the best writer but I hope this is understandable.

BMC

Edited August 9, 2005 by bmc5733946

[Cliff]

Modifications? Pah! I'm leaving mine standard.

I thought you were having issues? Did you resolve them?

[Guest Nogbad]

I thought you were having issues? Did you resolve them?

57504[/snapback]

 

I did resolve them largely. First I think I had a bad tank of gas, but balancing the TBs really carefully and checking the TPS made a huge difference. I now run only 98 RON. I still have the occasional hiccup on neutral throttle particularly between 3 and 4K rpm, but this seems common to standard 15M equipped bikes. I don't see how a PCIII could help with that, as a PCIII only trims the ECU signal. If the signal from the 15M is wrong, surely a PCIII simply gives you a trimmed wrong signal!

 

If I was planning to keep the bike forever, I would consider a My15M, but I am presently tempted by another bike and may change the V11 next spring. If I keep the V11 it will be as a second bike, and I wouldn't worry about the odd niggle then.

[Guest Jeff in Ohio]

I have made this suggestion before but will reiterate: whenever one encounters running problems with late model Guzzis it pays to check the spark plug caps!!!!!  I obviously cannot diagnose this problem from afar and so I may be wrong.  High plug cap resistance can lead to all sorts of running problems especially low speed steady state and transitional low speeds where spark performance is critical.  Higher engine speeds are much more forgiving of lost spark voltage. I personally have changed dozens of these caps that showed open circuits. NGK apparently has a problem, on my own bike I have replaced the wires with Magencor wires as I got tired of checking and replacing the caps every oil change, since the replacement I have had no low speed running problems.  I had lots of burps and farts before.  I work for GT Motors in Lansing MI, this is not an advertisment just a way to let you know that I truly have seen this a lot in the last few years.  I believe that the mixture these bikes are required to fire make this all the more troublesome. I have found bikes where I couldn't balance the throttle bodies accurately because of this.  5K ohms is correct value for these if I recall regardless most are marked on the cap. Good luck with your problem!!!!

BMC

57475[/snapback]

 

 

Which Magnecor wires? The 8.5mm ones or the Electrosports 7mm ones?

 

thanks

[Bbennett]

I had a similar problem today to the original poster and will pass along what I believe (fingers crossed) is the fix - at least for "my bike's" (2001 V11) problem.

 

Caution: I am no mechanic.

Symptoms: When riding two up I noticed a slight miss between 3-4K that I had not noticed before. My first thought this was not-quite-perfect PC-III map that exhibited itself only under "load" and in a notoriously weak part of the engine power curve.

 

Then today I was riding by myself and noticed the flutter between 3-4K when riding 1 up. Then things got interesting: I had a full misfire at about 5K...the bike literally seemed to turn off and on in a heartbeat.

 

I needed gas and filled the tank with 92 Octane.

 

The symptoms worsened. The bike would intermittently misfire under load (initially when going up a hill, and then seriously misfire when pulling off from a standing start). It got to the point where I could barely take off from a red light! The problem was "worsening".

 

I replaced the fuel - thought it might be "bad" . No improvement. I removed the PC-III. Did not fix the problem. Was there a fuel obstruction? Was the fuel pump dieing? ECU?

 

Then I noticed the negative battery terminal was slightly loose. Tightened it and Voila. I have not had the problem since - but have only ridden a few miles.

 

Thanks

Bob

[beauchemin]

Then I noticed the negative battery terminal was slightly loose.  Tightened it and Voila.  I have not had the problem since - but have only ridden a few miles. 

 

57578[/snapback]

 

It sounds like you nailed it!

 

As noted by others on this forum, a weak ground (or "earth", for those so inclined) connection is a CLASSIC cause of ignition-related problems (among others).

[jimbemotumbo]

Excellent advice here ... thanks all.

 

Here's the NEW plan:

 

1) Check elec connections to battery & ground

2) Check sensors (I haven't found the air sensor yet ... due to no airbox & mods)

3) SPark wires/caps (I have aftermarket wires but will check anyway)

 

May go back to a stock airbox, sans lid. I lost a pod the other day, so have to buy something anyway.

 

Thanks again all. I'll post success/failure.

 

JB