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V7 Classic, unreliable idle.

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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 25 Nov 2017 at 22:17
Originally posted by Vegas Pete Vegas Pete wrote:



I guess I’m just more comfortable around carburetors and vacuum tubes.

Vegas Pete.
I think that goes for many of us.
Brian.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Vegas Pete Quote  Post ReplyReply Direct Link To This Post Posted: 05 Dec 2017 at 03:07
Howdy, all!

I took the advice of the experts here and disconnected the lambda/02 sensor.  The first thing I noticed was that the idle seemed a little better and the mixture a little richer.  The stumbling idle instability persists, however.  I'm also getting an intermittent check engine light- usually a few minutes after starting.  Sometimes it goes away by itself, sometimes not.

So, it looks like it isn't a fuel mapping issue.

Thanks for the input,

Vegas Pete.
2010 V7 Classic, 2005 Ural Gearup, 1980 Yamaha DT175, 1973 Rokon RT-140, 1969 Rokon MkIII
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 05 Dec 2017 at 10:12
The check engine light could well be the lack of the O2 sensor. The ECU will expect an output but not see it.
And just because it's been removed won't always guarantee that the base fuel map is perfect.
 
If the light comes on is there a way you can read the fault code generated?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Vegas Pete Quote  Post ReplyReply Direct Link To This Post Posted: 05 Dec 2017 at 17:05
Howdy, Brian-

The odds are the light's telling me there is an issue with the O2 sensor.  In seven years of ownership the light had never came on until I disconnected the sensor.  

I have a harness to connect a laptop to the bike, which I think I've used once since I've had the bike.  Haven't seen it in years, but I'm pretty sure it's buried out in the garage somewhereConfused.  The other option is to take it to a dealer, but the one I've used in the past (350 miles away) no longer exists.  The Western U.S. is not what you would call Guzzi-dealer rich.

I guess I'll just keep living with it for now, and wait for something to fail catastrophically before making my next move.  Thanks for your help and input.  by the way, this forum is light years better than the Guzzi forum I belonged to when I first bought the bike.  That one was made up mostly of aging frat-boys who didn't seem to know anything but were always looking for an argument.  

Vegas Pete. 
2010 V7 Classic, 2005 Ural Gearup, 1980 Yamaha DT175, 1973 Rokon RT-140, 1969 Rokon MkIII
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Post Options Post Options   Thanks (0) Thanks(0)   Quote OldJohnboy Quote  Post ReplyReply Direct Link To This Post Posted: 05 Dec 2017 at 17:27
Originally posted by Vegas Pete Vegas Pete wrote:

Howdy, Brian-

That one was made up mostly of aging frat-boys who didn't seem to know anything but were always looking for an argument.  

Vegas Pete. 


Ha ha. LOL Sounds all too familiar!
But, as you say, not here.
This is my favourite biker forum, even though I don't own a Guzzi at the moment.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 05 Dec 2017 at 19:26
Originally posted by Vegas Pete Vegas Pete wrote:

After a while, you begin to recognize it has several distinct failure modes, which it shifts between as it feels appropriate;  there's the "no advance on one cylinder until the RPM drops almost to stalling speed" mode, the "miss one or two firing strokes in a row and recover" mode, and the "advance the timing until it's idling at 1800 RPM" mode.  The "no advance in one cylinder" trick is it's favorite- it will do this several times a minute sometimes, and then clear up with no explanation.  The other two usually won't repeat without a visit from the "no advance gremlin".


Just an idea, but could be a failing ignition coil. Or spark leaking to ground.



"Chicken nuggets don't dance on a Tuesday."
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 05 Dec 2017 at 19:34
I don't know the V7 series that well, but there must be a crank position sensor somewhere. These can collect metal swarf on them and mess up the ignition. Worth a check, I'm sure someone will be able to tell you where it is if you don't already know.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 05 Dec 2017 at 19:39
That's a good point actually. Even a dodgy connector for it could cause a problem.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Adam Quote  Post ReplyReply Direct Link To This Post Posted: 06 Dec 2017 at 06:38
Cleaning, checking sensors condition and associated wiring are certainly a good starting point, even renewing them as elimination process if it's not too expensive for you
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Vegas Pete Quote  Post ReplyReply Direct Link To This Post Posted: 11 Dec 2017 at 04:34
Greetings, all!

Thanks for the suggestions- they’re all valid. I’ve isolated and rejected as many possibilities as I can without actually replacing parts. The problem isn’t so much a “miss” as a weak firing stroke. It never fails to fire, it just doesn’t contribute enough energy to maintain idle speed, if that makes any sense.

I’ m still convinced it’s not a fuel/air ratio problem or an interrupted ignition issue- to me it’s an intermittent ignition timing issue that affects only one cylinder, and only for a couple of revolutions at a time..... and even then only at full-closed throttle.

I did a little Google research and found that the ECU has two ignition channels, one for each cylinder. That would allow one crank position sensor to fire each spark plug separately without using a distrubitor to get the timing right for both cylinders. This would also allow different timing for each cylinder. That would make for a cheap and easy way to stutter the spark to one cylinder for over-rev protection while causing a minimum of backfiring.

I’d love to sit down with a Magnetti Martello engineer, buy him a beer, and discuss the inner workings and design philosophy of this ECU.

Vegas Pete.
2010 V7 Classic, 2005 Ural Gearup, 1980 Yamaha DT175, 1973 Rokon RT-140, 1969 Rokon MkIII
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Adam Quote  Post ReplyReply Direct Link To This Post Posted: 11 Dec 2017 at 06:24
Are there two crank sensors or one sensor and two crank magnets?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Cylvabirch Quote  Post ReplyReply Direct Link To This Post Posted: 11 Dec 2017 at 06:52
Going back to basics: have you replaced both spark plug caps with new, genuine NGKs? Dave Richardson was advocating this on a post I read somewhere.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 11 Dec 2017 at 09:05
Originally posted by Vegas Pete Vegas Pete wrote:


I’d love to sit down with a Magnetti Martello engineer, buy him a beer, and discuss the inner workings and design philosophy of this ECU.

Vegas Pete.
I think many of us would love to do that. A lot of problems could be ironed out more easily if we knew more about the inner workings of the ECU.
 
Just one thing, a partly blocked injector could also produce your problem. Have you tried adding some injector cleaner to the fuel?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Vegas Pete Quote  Post ReplyReply Direct Link To This Post Posted: 11 Dec 2017 at 16:27
Brian-

I'll give it a try.... couldn't hurt anything.

Thanks,

Vegas Pete.
2010 V7 Classic, 2005 Ural Gearup, 1980 Yamaha DT175, 1973 Rokon RT-140, 1969 Rokon MkIII
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 11 Dec 2017 at 19:09
Originally posted by Brian UK Brian UK wrote:

Originally posted by Vegas Pete Vegas Pete wrote:


I’d love to sit down with a Magnetti Martello engineer, buy him a beer, and discuss the inner workings and design philosophy of this ECU.

Vegas Pete.
I think many of us would love to do that. A lot of problems could be ironed out more easily if we knew more about the inner workings of the ECU.


You'd probably need to be a computer programmer whizz kid to understand it tho.




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