V7 Classic weird problem!

I’m hoping someone can help. I’ve had a V7 Classic from new, bought in 2012 and have covered just over 9,000 miles without a hitch until now. I have had several occasions now when it loses power at part throttle. If I close the throttle and open it again I get power back for about two seconds before it happens again, or if I open the throttle more the power comes back and I zoom away until I ease the throttle back and it starts all over again. I’ve had it happen mainly on the motorway, twice at night, but it has happened during the day as well, and never on my first journey of the day. It is usually when I am returning from somewhere. I’m guessing that it is a sensor problem of some kind but where do I start to look please and does anyone know how I can diagnose it.
Thanks in anticipation - Peter (70sfan)

Hi fan, if you can eliminate contaminated fuel then sensor malf might be it.

Sorry I can’t offer any magic bullets, I’d have it to a dealer for an easy diagnosis. That said, I would have a visual on the lambda sensor embedded in the collector box, which is exposed to the spray and grit under the bike. Check for insulation breakage and correctly seated.
Hey and try the Search facility here, I’ve some dim recollection of a problem with the early single-throttle-body V7s.


If this is a single throttle body motorcycle< AND you suspect it is lambda sensors then I suggest

Switch off machine
Remove the side panels
Find and disconnect the lambda sensors from the loom - on my V7 Stone they are amp socket and plugs.
Cover the ends with tape for now and tuck away so they don’t catch or get damaged
Fire up motorcycle
Drive as normal

The ecu on my model doesn’t report a fault or bother with a loss of lambda sensor(s) so you can drive as normal.

It may be worth checking your plugs too - I find the Stone eats them.

Co-incidently I reconnected my sensors about half an hour ago to see if the symptoms have disappeared. There was quite a thread on this here and on other forums - WildGuzzi as well as a piece by Roger Shufflebottom in Gambalunga IIRC.

Thanks - looks like lambda sensor may be the issue. Will check the plugs as well though.

Thanks Phil - will investigate. Incidentally I’m flagged as a non-member even though I am a member any idea how I get that changed?

Drop an email to the forum officer with your name, forum name and membership number and he should be able to sort it out.

Cheers - thanks

Its not clear that the sensors are the issue. It has been suggested the MIU ecu runs closed loop using the lambda sensors to provide the correct mixture to meet emission criteria. This is in the range up to approx 3500 / 4000 rpm.
Above this rpm the MIU uses an open loop map which is why the “weird effect” clears once the rpm rises to + 4k rpm.
Note that this is my take on it and it is not based on much verifiable fact.
I cannot vouch safe for extended running with out sensors online as the AFR in the lower range is unknown to me. If it is weaker then obvious damage could occur. Again, anecdotal evidence suggests this is NOT the case. I am sure someone out there will have the data to prove this is bollix, a fact, or something Guzziish inbetween.
The V7 stone runs lean - the pipes are quite blue.

Need more chit chat on this problem - its onset and unpredictability is dangerous in my opinion.

Other thread here:Â http://www.motoguzziclub.co.uk/phpbbforum/viewtopic.php?f=2&t=21970&p=280372&hilit=lambda#p280372
and here:

Struggling a bit with the TLAs here. What is MIU and AFR please? I think what you are saying is that above 4,000 rpm the ECU (this one I do know) ignores the lambda sensor - is that what you mean by open loop and closed loop?

Thanks for continuing to put thought into this. I’m currently awaiting new spark plugs, as the first and simplest fix, but it would be good to get to a root cause. I have also been running the Finebau product, but took this off when I first noticed the problem thinking that might be causing it. It wasn’t, as taking it off had no effect on the problem but got me back to poor low rpm running. Agree about the V7 running lean. My pipes have blued magnificently.

Sorry, basic MIU info here at bottom of page:http://www.magnetimarelli.com/business_areas/powertrain/motorbikes/ecu.

AFR is air fuel ratio - the mixture of air to fuel burnt in the engine. As AFR decreases, mixture changes to richer and vice versa. Rich is preferable to lean if experimenting. Open loop is where the fuelling is preset for given rpm and throttle positions and generally not affected by lambda sensor feedback, closed loop is where the lambda sensors measure and feedback the o2 level which is an indication of too lean or too rich a mixture and corrects the injection duration to try and achieve the optimum AFR. Â Before the weekend I had plugged the lambda sensors back in and on the Saturday (64 miles) there was not really any hint of bogging down, however yesterday on my return from the west coast there was a noticeable dead band about the 3.8k rpm and up to 4.2k rpm. This is on partial throttle openings and clears when throttle is opened but there is a significant increase as if fuel was injected all of a sudden. On backing the throttle off again from WOT and letting the rpm drop to the problem area the bogging down reoccurs.
My machine doesn’t exhibit other foibles such as hunting at idle or poor starting which has also been recorded, it’s only the bogging down that gets me. By continually experimenting yesterday it seemed as if it would “clear” eventually . After wide open throttle, and then easing off to just open, to maintain 60 mph in top, the bogging down would reoccur. Just about the spot for legal cruising too!!
My plan is to have a chat with my local Dyno centre and book a wee session where I run the bike up and down checking the AFR with O2 sensors on line, then offline to see what, if any, effect it has on the performance. On the V7 Stone 2013 the two injectors are controlled independently although there is one throttle body / ecu so it could be a sensor and not necessarily the O2 one. There are air temp, air pressure sensors too which all influence the fuelling. Pain in the bum tho’

I have left off Daves gizmos for now also just to take them out of the equation.

Of course there could be many other causes, fuel tank pulling a vacuum, fuel quality, filter blocked, pump not working correctly, heated grips interfering with throttle operation, all varied and basic stuff but the fact is that at wide open throttle (WOT) the bike pulls like billy oh! At throttle settings of 1/4 or so it doesn’t.

Bizarre - I am as interested as you in bottoming this out as it interferes with what is a fine motorcycle otherwise.

edit:Â Just a thought - could you check your plug gap and tell me what its set at please?

I have a horrible feeling that basic maintenance may be the answer. The new plugs arrived this morning and looking at the old ones, they are knackered and had a gap of close to 1mm! I’m surprised it worked at all. I shall be going on a 100 mile round trip this afternoon and will report back.

I am considering increasing the gap on my plugs to 0.85 / 0.9 mm as also discussed on the WildGuzzi site by some posters. Think book setting is around 0.65 mm - need to check on return home. Also ordered GuzziDiag leads from LonElec to see if I can connect & have a look at the map. It’s unclear if GuzzDiag presently covers the MUI ecu but I’ll have a go next week.

Thanks, yes I’ve set my new plugs to .65mm. However now things are even worse. I was only about five miles out when the problem started this time. (I had to turn round and get in the car instead…ugh.) It was just enough time for the engine to warm up I think. It is not so much revs dependent more about throttle position as I was keeping an eye on the revs and it would happen anywhere between 2,000 and 5,000 rpm, on about one quarter to one third throttle opening. Tomorrow I’ll do a visual check of the lambda sensors. There are two on my bike, one for each pipe.

0.65 is near as dammit 25 thou (as in imperial, of an inch) think I typically have mine set as that. Typically HT is around 20,000V which is roughly correct for 0.025" and a compression ratio of 10:1 (gas density in combustion chamber = 10 atmospheres), 1mm might be pushing it a bit requiring maybe >30,000V or more. HT insulation becomes more of an issue then also back EMF on the primary will be higher as well. Not generally good news for electronic ignition, unless it has over-Voltage protection of some sort.

Try disconnecting the sensors. Keep the plugs as they are for now.

Just to say, following interestedly :nerd:


Peter, has your m/c had any map updates by dealer? Also what mileage are you on?

It hasn’t been near a dealer since the first service. Mileage is just over 9,000 miles now. It has had one service from me about a year ago.

worth checking the fuel filter in the tank?

Probably is, however I can’t see how the filter would affect the 1/4 throttle but not wide open throttle setting. If blocked would it not cause a problem through out the range of throttle. Is there some dump v/v on the fuel pump circuit internal of the tank that maintains a constant-ish fuel pump discharge pressure to the injectors? My Sportie has such a device (external) which shreiks like a banshee on pump prime then settles down.