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problems with fuel injection system

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linda and mark View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote linda and mark Quote  Post ReplyReply Direct Link To This Post Topic: problems with fuel injection system
    Posted: 13 Sep 2018 at 22:44

Hi Everyone.

We are new on here and total technophobes, so please excuse us if we do this wrong. We used to ride Guzzis from 1980 until 2004, our first one being a V50 2 and the last one being a Jackal. Then we were out of the country for a while, but we have finally got a Nevada 750. She's a 2016 model that we bought in May and she's a great little bike, but we are having problems with her popping and back firing, mainly at low revs in town traffic.

Fortunately the shop that we bought her from has given us a 2 year warranty, but after taking her back 3 times, nothing has changed. It has been an 80 mile round trip to the shop and as of next week this is increasing to 200 miles. So we really want to get it sorted out.

The service department is now claiming that it is something called over run, which we have never heard of. Apparently all bikes with fuel injection systems have the same problem, ie when you shut the throttle off, there is too much fuel being delivered so the bike back fires as it burns this off. Now we know absolutely nothing about fuel injection, but ours would fail the noise restrictions if nothing else. She can rattle windows when she is really bad.

Our jackal had fuel injection and never gave us any trouble at all. Plus we had a V7 3 loan bike the last time we left our Nevada at the shop and that didn't have any problems either. Ours hardly ever causes any trouble at speeds over 40 mph and at 70 mph we can shut the throttle off as hard as we like and she hardly even burbles. But cruising along the flat, going up hill and mostly going down hill, even under load, is virtually guaranteed to get her playing up when in town traffic. This equates to around 30 mph in second or third gears, at 2000-3000 rpm.

Has anyone else heard of this problem before please? We've tried searching Google and came up with the following explanations for cars:

'To minimise waste fuel on the overrun, the fuel pressure regulator reduces the amount of fuel that can pass through the injectors from the usual setting by vacuum control.'

'On deceleration, the throttle butterfly is closed, so vacuum is at its greatest. This vacuum pulls on the fuel pressure regulator and this reduces the fuel pressure by about a sixth. Therefore, in the same time, less fuel enters the engine via the injectors.

We don't understand much of this, but assume it is the same for bikes?

Thank you in advance for any help you can give us.

Best wishes

Linda and Mark

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BobV7 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BobV7 Quote  Post ReplyReply Direct Link To This Post Posted: 13 Sep 2018 at 23:09
It is generally accepted that popping on overrun is due to the fact that engines are now required to run very lean in order to conform to current emissions legislation. Quite like it myself.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 13 Sep 2018 at 23:18
Yes, it is quite common due to the need to comply with the new Euro pollution regs.

Some bikes seem worse than others, and the type of exhaust can affect things too.

Any small leak in the exhaust can cause this too though.

There are gizmos which can help, google "fat duc" for example. The other thing which has worked for some is to disconnect the lambda sensor(s). These are screwed into the exhaust and will have 4 wired coming out connected to the bike loom.
Brian.

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rapheal View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rapheal Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep 2018 at 18:59
My Breva ( same engine) used to drive me mental with the popping on the overrun
and juddering below 3k so much so I considered selling it and going back to an old airhead
however a nice club member told me to get a widget thigny and fit that
it was farily easy to fit even for a cretin like me
whip off the r/h side panel disconnect a connector form a thingy and insert new wires, connect old wires to thingy
fix box of magic juju under seat with self adhesive tape
then install some sort of metal thing out of the heat from the engine, so I fixed it to teh rear mudguard by the number plate
then I took it for a 50 mile ride
initial acceleration much smoother and stronger
no farting on the over run
no juddering at low revs

the other option I am told is to remove some sort of Chip ( french fries ??) and send it away to be re educated
no good me doing that the bike would be knackered



Edited by rapheal - 14 Sep 2018 at 19:16
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BondEquipe View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BondEquipe Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep 2018 at 20:01
Just to clarify: "the over-run" is just a term for that period when you close the throttle and the engine is turning at a speed that is greater than the throttle opening would normally relate to. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kriegmob Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep 2018 at 22:40
I've been chasing around the same back-firing on de-accleration for a while now. My 2007 Nevada is running better than ever, except for that. And, like some others have mentioned, I kind of like the back firing, sounds cool to the part of my brain stuck in adolescence.  

I would suggest you check the exhaust manifolds at the motor. I noticed the popping from my left cylinder and sure enough the mounting bolts on that exhaust were finger loose. Cranked those down nice and tight and it's a lot better. Perhaps yours have loosened up.

Also on the left cylinder the spark plug cap feels a little loose and wobbly. I've ordered new caps and wires to replace to see if that helps out as well.

Ben
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep 2018 at 22:46
They all do it to some extent though. I think some riders are more bothered by it than others.

On my Norge, I find if I hold the throttle open a gnat's the popping doesn't happen. It only happens when closed completely.
Brian.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jefrs Quote  Post ReplyReply Direct Link To This Post Posted: 15 Sep 2018 at 07:40
Popping on over-run is common on any electronic fuel injected bike. They do not have the more sophisticated systems cars have to prevent it.
One effective method of prevention is remapping so that zero throttle and high revs cuts the fuel supply from the injector off. This can be done with a Power Commander (PCV) but it is an expensive option and I'm not sure they can be used with a Guzzi (it depends on ECU). 
My V7II does not pop on the over-run, they've probably fixed the map; my Enfield EFI is a devil for it despite having a PCV map that mostly cures it.
On Brian's Norge the map may have been 'fixed' at 2% or 5% throttle but not 0% throttle, causing it to pop when fully shut but not when lifted.  On my Enfield I can encourage a very loud bang by shutting the throttle and then lifting it slightly again, because it cuts off fuel at zero throttle and puts it back on at 2% (until the revs drop to near idle where the fuelling returns to normal)

I've been playing with the Lambdas connected and disconnected. I doesn't make much difference to the rough pick-up but clearing the lookup tables does. The lambdas store data to two lookup tables (maps) that can be cleared by disconnecting the battery or the main fuse. It would appear the tables can get skewed by outlier data; clearing (or resetting) allows the system to repopulate with fresh data (think reboot the computer).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote c13pep Quote  Post ReplyReply Direct Link To This Post Posted: 15 Sep 2018 at 11:44
The original post mentions `rattling windows` and failing a noise test, if this were the case then surely this cannot be `over run `cackling` as we used to call it, this must be excessive unburnt fuel entering the exhaust!
The exhaust should be the first check for any air leaks even if only minor and only after this can it be put down to poor fuelling.
Of the three fuel injected bikes I have owned (two 1150 BMWs and a little 125 Yamaha) I have never experienced any `cackling` on over run, with fuelling on all being pretty much spot on, perhaps I've been lucky, but I would hope not.(all have been standard bikes)
CHRIS
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BobV7 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BobV7 Quote  Post ReplyReply Direct Link To This Post Posted: 15 Sep 2018 at 12:12
The OP wouldn't be slightly prone to exaggeration by any chance, would they? Concorde used to rattle windows and I don't really think an ittsy bittsy motorcycle petrol engine compares with that!LOL
V7 Classic Black and gold was the best. But green & black was nice too. Now blue is in!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ranton_rambler Quote  Post ReplyReply Direct Link To This Post Posted: 15 Sep 2018 at 14:06
Someone I know has a Le Mans that sets car alarms off.
But I agree about sorting out air leaks first. That's what sorted the overrun noise on my SP1000. Not sure if it was induction or exhaust as I went round and tightened all the joints.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jog53 Quote  Post ReplyReply Direct Link To This Post Posted: 15 Sep 2018 at 14:20
My 1995 Cali 1100i pops and farts furiously on the over-run. I would genuinely be disappointed and concerned if it stopped doing so.....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jefrs Quote  Post ReplyReply Direct Link To This Post Posted: 15 Sep 2018 at 15:02
My Enfield EFI can snap and crackle on the over run but when it decides to make a bang it's like a cannon going off. It is essential to make it do this going through a tunnel. By comparison my V7II makes a gentle burble on over-run.  
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