Stumbles and backfires at low rpm

[Flatland Dan]

Well, I finally found someone who could run me over to pick up my bike on a workday. Started perfectly but, 55 miles down the road, it all started in again. As long as I was cruising along at 3750 rpm or better, there was no problem. I am sure it is a heat related problem because when I got back into town and the engine warmed up some more, it started into backfiring and farting like crazy. Guzzi technical services told the mechanic that it was a fuel related problem. To me it sounds more like a timing problem. I had an old Chevy that had a bushing wear out on the distributor. Timing changed constantly. Will put a timing light on it with a cold engine and then again with a hot engine. Suspect I will find a difference. I'm starting to worry though, as I am running low on homebrew. Later, Dan

[Guest GGuzzi]

Well, I finally found someone who could run me over to pick up my bike on a workday. Started perfectly but, 55 miles down the road, it all started in again. As long as I was cruising along at 3750 rpm or better, there was no problem. I am sure it is a heat related problem because when I got back into town and the engine warmed up some more, it started into backfiring and farting like crazy. Guzzi technical services told the mechanic that it was a fuel related problem. To me it sounds more like a timing problem. I had an old Chevy that had a bushing wear out on the distributor. Timing changed constantly. Will put a timing light on it with a cold engine and then again with a hot engine. Suspect I will find a difference. I'm starting to worry though, as I am running low on homebrew. Later, Dan

That sucks I am hoping that I hear a success story from you soon as mine in sitting idle as we speak.

[Guest rotorhead]

These symptoms are almost exactly what I had....I still side with the inlet air temp sensor in the airbox....mine caused an extremely rich condition causing bucking and surging. Guzzi rep only found this after changing virtually everything else starting with the most expensive item and working his way down the cost expediture pole

 

It will be interesting to see how you fix this.

[Cliff]

Yet, Dynojet sells an adapter that negates the O2 sensor on closed-loop bikes to "improve performance"

 

Interesting... I don't know what to think on this one....

 

I think their main reason to claim this is because their PCIII won't work with a closed loop system.

 

Open loop is good when you have the map right but even a service can throw that out. I got a 10% variation in TPS sensor just adjusting the balance as my idle stop is on the LHS and the TPS on the RHS. Having closed loop will counter these variations and others. My bike feels noticably better closed loop.

 

Of course its all in the implementation. Who knows exactly how the WM closed loop works. Is it only for a small portion of the map. How quick is it to respond?

 

IMHO closed loop is the way to go - with a wideband sensor. At the moment I don't do anything fancy with wideband as I only have one target A/F for the entire map. I can, through the Optimiser or PC Controller, go economy or power if I want.

 

In the future I will have a variable target A/F depending on what section of the map is running.

[Guest Bob in CT]

Sounds like it starving for fuel. Maybe the tip-over valve? Stop and open the gas cap when it starts giving you a problem and see if it goes away.

Good luck

Bob

[Flatland Dan]

The suggestions given sor far, steps I've taken so far, and the results so far.

Bob in CT.--Starving for fuel. Ran the bike for a couple of miles with the gas cap open and also checked for pinched lines. No luck. Al--ECU and valve lash. The dealer does not have another LeMans in the shop and the clearances are good. Big Unit--Water in the tank. I have run 3 tanks of gas through her now and still am having the problem. Mike Stewart--Stock exhausts? Yes, but I have FBF cans coming soon. The dealer offered them to me at cost minus to take care of the dents that they put in the stock ones. gthyni--remap the ecu. The dealer says that cannot be done. Is there a difference between Euro-spec and US-spec? Rotorhead--the air temp sensor. I think you are onto something. It only misbehaves when the air temperature is hot. I took a long ride today in upper 60 degree temperatures. About 15 miles in town-BORING-and about 40 miles in the countryside. And it only popped once. And that included about a 5-8 minute stop with the engine idling to get it good and warm while talking to a fellow Guzzi rider at a road construction stop. Definitely a heat issue me thinks. Will coerce the dealer into changing out the air temp sensor this weekend and see if that helps. Thanks for all suggestions. Later, Dan

[gthyni]

gthyni--remap the ecu. The dealer says that cannot be done. Is there a difference between Euro-spec and US-spec?

 

Which means he can't do it...

 

Check out FIM

[al_roethlisberger]

Al--ECU and valve lash. The dealer does not have another LeMans in the shop and the clearances are good.

 

 

Well, two things(actually three )

 

1) Any ECU from a recent V11 Sport, Naked, LeMans... will work. They are all the same. So if he has any of the V11 Sport "models" on the floor, he can swap out the ECU in about 15 minutes.

 

2) WRT valve lash "clearances look good" ... what does that mean? I ask because if he is simply saying that they are set to the "correct" US/North-American spec, then they are probably too tight for your local heat/weather. This is a common problem with many US bikes, as the valve lash for the US is a good bit tighter to meet EPA sound regulations, but is often too tight once the engine is heated up in hot climates to idle. This is the exact problem I went round-and-round with my dealer for MONTHS to get my bike to stop coughing, knocking the intakes off, and dying at idle once run up good and hot. It was extremely frustrating, with several trips to the dealer..... with them finally saying "oh, just go ride it and let it loosen up" Well, I gave up... and took it home to fix it myself, and once Mike Stewart and I loosened the valve lash up to Raceco specs, it's never coughed or died again. Never. I would suggest asking if he measured/meant US, Euro, or ??? specs. And if he said US, ask him to loosen them up to Euro specs at the very least to see what happens. Raceco specs are even "looser".

 

Now, this may or may not be your problem of course, but be sure to ask the dealer exactly what "the clearances look good" really means, as it does matter.

 

3) And WRT remapping the stock ECU, as Gthyni points out... his answer that "it can't be done" is hogwash. Even my dealer, who I have some minor nits with(see #2 above ) is/was able to remap the air/fuel portion of the 15M with the supplied software from Guzzi with no problem. They have to be able to do this, in combination with a gas analyzer, to properly tune the bikes when servicing them. If you dealer can't, then he needs to have his service guys go to "Guzzi school"

 

The only portion of the 15M that almost all capable dealers won't mess with is the ignition map, which is apparently harder to tinker with.... either for technical reasons, or perhaps due to lack of experience

 

And even though most can do the fuel/air map, they don't have a dyno or the experience to tune it to produce the best power... just a good burn/idle to spec.

 

 

 

Anyway, hope it all works out for you. It's got to be something simple, as these engines just aren't that complicated. And once you do find the little nit giving you these problems, you'll just shake your head that it took so long

 

Good luck, and let us know how it works out

 

al

[Flatland Dan]

This is probably the most knowledgable, helpful, and enthusiastic group of people there is!!! Later, Dan

[Keith Foster]

Hi Dan, I offer the title below to my experience with my Nero.

 

My New V11 Nero Corsa picked up this week ( edit: added link )

 

The good thing is, now 1000 miles later, the Guzzi is sweetly crusing along.

 

So my vote is to swap out ECU's. And I agree with Al, they are the same ECU's from the different models. I did notice my replacement ECU was different (meaning markings and such on the data plate) from the one that the bike had on when I picked it up.

 

And the dealers can reprogram/tweak the ECU programing. My my dealer has mentioned it several times.

 

Good luck, something will turn up!

[Bruno]

Hello,

 

I've been reading through the posts and have a few questions. Although I do not have the any of the problems which started this thread, I have found that the engine on my 2002 LeMans quits on occasion when hot.

 

Based on Al's input, I'm wondering if the valves may be set to tight. I've only 470 miles on it and will be doing my own servicing next weekend. This being the case, Al, you mentioned that the clearances should reflect the Raceco specs. Could you, or anyone, post them?

 

I should be asking if doing this is a good idea too!

 

Bruno

[TX REDNECK (R.I.P.)]

you can find this in the FAQ section & yes its a good idea

 

http://www.v11lemans.com/forums/index.php?showtopic=611

[Mike Stewart]

Hello,

 

I've been reading through the posts and have a few questions. Although I do not have the any of the problems which started this thread, I have found that the engine on my 2002 LeMans quits on occasion when hot.

 

Based on Al's input, I'm wondering if the valves may be set to tight. I've only 470 miles on it and will be doing my own servicing next weekend. This being the case, Al, you mentioned that the clearances should reflect the Raceco specs. Could you, or anyone, post them?

 

I should be asking if doing this is a good idea too!

 

Bruno

Bruno,

 

The Raceco specs. are .008" intake, .010" exhaust. The valve train will be slightly louder with these specs. but the bike will run much better in the lower rpm. range.

 

Some owners split the difference between factory specs. and Raceco specs. and use .006" intake and .008" exhaust.

 

The valves are so easy to adjust, I would start with the Raceco specs. first to see if it solves your stalling issue. Also, check your throttle body sync. after the valve adjustment. It tends to change if the valves were off.

 

Good luck,

Mike

[RacerX]

I think their main reason to claim this is because their PCIII won't work with a closed loop system.

Dynojet has spent a large amount of time (and money) researching closed-vs-open loop systems, and has proven to the vast majority of people (including most ALL of the AMA Pro Racing Teams -- why this is continually ignored on these webboards is beyond me) that open loop is simply the most cost effective way to make a bike run properly. The bikes other sensors; i.e. barometric, head temp., etc., all do a very decent job at keeping the bike running well... and if you say not, then the engineers at Magneti/Marelli must be slackers, eh? (Hey don't they do Formula1 cars too?). While the 1.5M system is not perfect, and actually quite barbaric in the World of F.I., it does a reasonably decent (& reliable) job of keeping the bikes running well comparably.

 

Of course its all in the implementation. Who knows exactly how the WM closed loop works. Is it only for a small portion of the map. How quick is it to respond?

I, through Dynojet, know exactly what portions of the OEM 02-sensored M/M systems are closed/open, and how quickly they re-act and function/adapt.

 

Dynojet will be finalizing a 02-sensor block-off forthe M/M Guzzi system very soon.

 

I currently have two PCIIIusb protoypes running on US-Spec Breva 750's, with good results, and without a block-off sensor... yet.

 

Heh, nope Antonio... PCIII's will not cure all bad running Guzzis. I so wish they would.

 

$.02,

Todd@GuzziTech.com

Certified Power Commander Tech

[emry]

I just noticed something funny when I pulled off my rear hugger.... The Moto Guzzi SPA information tag. You know the one with all the adjustments, idle speed, mixture, etc. Guess what it says for the valve clearence...

In: 0.15mm +-0.02mm Ex: 20mm +-0.02mm.

 

Exactly what I am running because my bike would not idle when warm with the SPEC's that were published in my manual and to the dealers.

 

I agree with those who have stated that MG tightend up the clearence to make noise limits, loosening them up do create some extra noise and it sure does sound good.