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Breva 750 'hickups'

RJVB

RJVB

GT Reference
Joined
Oct 28, 2008
Messages
1,936
Location
Paris
There've been several reports/complaints about Breva 750s acting up on a French forum, behaviour that's described as hickups or gaps in the injection. It reminds me a bit of what's been discussed here concerning Californias, which seemed to be related to a faulty TPS module, but I'm not sure that's the right diagnosis here. So:

- on one bike (Euro-2), it happened at high regimes, which apparently was diagnosed as due to a faulty O2 sensor, and remedied after replacement. It's now doing it again, but at low regimes, less severe, but enough to require aggressive throttling to avoid stalling. The fuel filter has been replaced without effect, valves were done less than 2k km ago (bike has 64k km).

- one bike had similar symptoms, but only on a cold engine and the sump filled with 5W40 - not half full or filled with 10W50...

- a third bike also has similar symptoms on a cold engine, between 2k and 3k rpm, small hickups at about 4k rpm stabilised when the engine is warm (injection hunting?)

- a fourth bike, difficulties to stabilise the regime between 2.5k and 3k rpm on a cold engine. A synchro didn't resolve everything, but he discovered his ECU is only receiving 11.7V, which could be a cause of the problem according to his mechanic.

So, in most cases this appears to be something that has to do with the engine being cold. I don't really believe the 11.7V-is-less-than-12V ECU explanation - if that's a digital computer thingy, it either works or it doesn't...

Any thoughts? I don't recall ever reading about this kind of issues with the B750, on here!
 
On the low tension, I do remember the BMW ABS-systems being very unreliable when so happens. Guess they are computerized as well. So maybe anyway.

Thanks for your input!
 
Rene,

Holt may have something here. The BMW ABS computer is very sensitive to supplied voltage. If voltage drops below a certain level on start up it will trigger an ABS fault that has to be reset. The bike will run fine, but the ABS fault will not go away until it is reset.

The 750 may be in a similar condition where low voltage impacts performance until voltage rises (engine warms up). My course of action would be to monitor battery voltage during start up, and if it drops below 12 volts, replace the battery and see what happens.
 
Haven't heard of those issues before so it will be good to follow up and see what they come up with.
 
I'm going through similar too. I've had the bike tuned/sync'd etc. and it ran correctly for awhile (after being brought in because of low throttle surging and excessive backfiring). Now it doesn't "pop" as much, but I'm starting to stall at intersections and, coming off of a ferry last week, heavy surging at low RPM. The scary kind. Enough to make me stop in traffic, rev the hell out of the engine and then continue on my way.

Everything seems cool above 4k RPM, but below that it's never really run properly since new. No warnings appear when hooked up the ECU. Voltage seems fine as does the idle etc..

It's going back to the shop as soon as I can to get it looked over and find out what's going out of tune so quickly.

One thing that DID help awhile back was to pull the battery for a half and hour or so. When re-connected, it seemed to behave itself for a bit. Some have suggested this resets the "history in the ECU"? A bit beyond me, but perhaps worth a try.



RJVB wrote:
- on one bike (Euro-2), it happened at high regimes, which apparently was diagnosed as due to a faulty O2 sensor, and remedied after replacement. It's now doing it again, but at low regimes, less severe, but enough to require aggressive throttling to avoid stalling. The fuel filter has been replaced without effect, valves were done less than 2k km ago (bike has 64k km).

Any thoughts? I don't recall ever reading about this kind of issues with the B750, on here!
Click to expand...
 
Flay,

This is beginning to sound like a bad batch of ECUs. What you are describing is what I ran into recently with a Jackal. Ran horrible at idle, couldn't get it to idle, died at stops but Ran OK at high RPM. No ECU errors presented with diagnostic software. After exhausting all other possibilities I borrowed an ECU to try. All the symptoms went away.
 
A bad batch of ECUs, or (a batch of) ECUs that go bad after a while (this doesn't seem to affect a particular batch of bikes).

How hot do those circuits get and/or how well are they cooled?


Edit: voltage may seem fine on a standard multimeter
 
Rene,

I think you are over analyzing here. As for running off a separate battery, forget it. Electronic failure rates tent to follow the "bath tub" curve. High failure rate when new, then drops to practically none, then when old the failure rate rises again. Both of the failures I know about where at each end of the curve, one a new bike still under warranty, the other a 2000 with over 150K miles.
 
Very strange, however I have to admit that on this years USA trip,occaisionally the bike slowed down, Breifly, then caught up again, I thought it was mebbe me somehow easing the throttle,unintentionally.
It only happened a couple of times, and in the mountains, so it never became an Issue.
However next trip, I will keep this in mind and see what happens.
I do however have to say, that the Guzzi workshops that you find in the states,seem pretty basic,( Heck some states do not even have a Guzzi agent) so expecting to find an oscilloscope may be asking a bit much.
Take Care Out There.
(OK I can only speak of the workshops I have seen)
 
Hi, Back again.
Hey FLAY, how many miles on yr bike, I just checked my notes, Yes the bike is still over there and I am back on the boat, anyway I have 26.396 on mine.
Am I being an idiot here, or didnt someone mention cleaning the Lambda sensor to clear misfires ? or am I mixing two things up ?
Take Care Out There
 
John:

I think it depends a bit on one's mindset w.r.t. the ECU. If you consider it some blackbox component, to be changed whenever there's a doubt: sure, I'm over-analysing. Change it, and if that doesn't help, it wasn't the ECU. Doesn't exclude issues with the powersupply and/or the effect of interference, though.

If you're trying to understand what's going on and/or if you just don't have a couple of spare ECUs for each model lying around ... is it really so much over the top what I'm musing about?

I must admit I indeed have no idea how likely it is to find an oscilloscope in an average MC workshop. That might have to change though, now that vehicles are more and more dependent on electronics rather than "simple" electrics!
 
Yea But, Yea But, RJVB, you didnt answer my question about the Lambda Sensor?
Didnt cleaning that, make all the bad things go away ??
:laugh:

Holt ! Holt ! Where is Holt when you need him ?
Holt, RJVB is ignoring me, What was that about the lambda sensor ? :huh:
 
motoguzziman wrote:
Yea But, Yea But, RJVB, you didnt answer my question about the Lambda Sensor?
Didnt cleaning that, make all the bad things go away ??
:laugh:

Holt ! Holt ! Where is Holt when you need him ?
Holt, RJVB is ignoring me, What was that about the lambda sensor ? :huh:
Click to expand...

Sorry, haven't got no clue at all. I've got one of them flawless
 
Thanks guys, I knew I could count on you, now we just have to hope the glitch gets fixed.
Any updates would be greatly appreciated, as said, the two hiccups I had were in mountains, going upwards and were very brief,I thought mebbe the throttle had slipped under my glove, and never thought any more of it, until getting back to the boat and reading this article.
You all take care out there!
 
On another board a Breva owner had intermittent power loss. Bike would stumble before picking up again and driving normally. After trying everything he found the problem was blocked fuel tank breather nipples.

link to breather issue

Consider this another issue to be aware of.
Joe
 
motoguzziman wrote:
Yea But, Yea But, RJVB, you didnt answer my question about the Lambda Sensor?
Didnt cleaning that, make all the bad things go away ??
:laugh:

Holt ! Holt ! Where is Holt when you need him ?
Holt, RJVB is ignoring me, What was that about the lambda sensor ? :huh:
Click to expand...

One thing more;

As soon as you guys begins talking about electronics and IC circuits and that mumbo-jumbo, I'm desperately looking for the nearest emergency escape!
My motto is "Not a volt below 230!".... :unsure:

But error and trial usually will do it.

Ren
 
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