Breva 750 Cutting Out

[MikeW]

My wife's Breva 750 has started cutting out randomly on the freeway. It's done this around four times over the last 5 weeks. It usually happens at cruising speed but sometimes at idle. Sometimes it comes back to life. Other times it needs to be restarted.

Of course it never does it when I ride it!

I've checked the side stand cutout switch and it's working properly. Since it was due I changed the fuel filter and in a moment of desperation dropped it off with the dealer to have the EFI checked out. They checked for error codes, checked the TPS, did a throttle body balance, set the valve clearances and changed the plugs.

Today it did it again!

Any ideas of what I should try next? I thought it might be worth bypassing the side stand cutout first but I'm suspicious it is a electrical issue somewhere else or perhaps even the fuel pump.

Mike

[Kiwi_Roy]

I'm not exactly sure about how the safety logic works but obviously relay 38 must remain energized while the bike is running to hold the main injection relay ON

http://www.thisoldtractor.com/guzzi007/schematics/2004_750_Breva.gif

As I read it the relay 38 is held on first of all by being in Neutral then later by the sidestand switch while in motion

I think the problem is most likely the sidestand switch either a bad contact or the stand is partially deploying with vibration.

If you unplug relay 38 and measure Ohms from pin 2 to chassis then exercise the stand switch it should go from open to near zero cleanly, anything over 0.5 Ohms and I would order a new switch.
(you might need the bike in gear while you do this so the neutral switch is open)

The whole idea of the logic is to prevent you accidentally starting on the stand in gear, I think loosing power in traffic is a bigger risk. This is the reason the stand switches have been bypassed on 90% of the older bikes.

BTW, the connection to dash pin 18 just lights up the Neutral light.

Let's wait and see what other Breva owners have to say about this.

[biking sailor]

My Wife's 2007 Breva 750 did something similar.  I had just given it a 18,000 mile service (all the fluids, and valves, left in the same plugs and didn't touch the throttle body balance or TPS, as that all seemed OK).  When about 500 miles into the trip, it started to miss sporadically and cut out, along with filling the breather oil overflow tube with oil (pull the plug out and it would leak a 2 to 3 inch circle of oil after every tank full of gas along with slowly dripping out past the plug while riding).  I chalked it up to my overfilling the crankcase with a bit too much oil and it was accumulating in the breather box, then being sucked into the throttle bodies.  When I got hot it home (after worrying every mile that it was gonna die on her at the worst time, it would go through periods where it wouldn't idle without added throttle), I cleaned the breather box and sprayed down the throttle bodies and all has been well since (about 4 or 5000 miles).

I never felt like ours was electrical, after my initial testing on the road, with limited tools.  I did pull the plugs when it was acting up it's worst, and they had the look of a bit of oil on them.  Good luck on figuring yours out!

[MikeW]

I measured the resistance of the side stand switch as suggested and it was around .3 Ohms.

I've bypassed the side stand switch for the moment and so far the bike hasn't faulted. I'll give it another week before ordering a switch. The list price is around $100 AU in Oz so it's not a swap and see how it goes sort of price!

Mike

[ITSec]

The sidestand on this bike is notorious for gradually shifting downwards during a ride, leading to the engine cutting out. This can occur on any roads, but on my former bike was particularly prone to occur on the highway.

Since you've already tested the switch, if the bike has a center stand (and your wife will use it), then tie the sidestand into the up position and try riding (with the switch back in line). Or, if the side stand must be used, clean and heavily lubricate its hinge point - or even insert a couple of very thin washers on either side of the stand's hinge along with the lube. That solved a similar issue for me and as far as I know the current owner still has no problems in this area.

[Kiwi_Roy]

Since the Breva also has a clutch switch I assume the lever must be pulled in so the bike will crank.

The stand switch would be safer if it were shorted out IMHO, it's better to risk an unexpected takeoff rather than loss of power in traffic.
Roy

[Triple Jim]

Just something to consider... I knew a guy who died because he left his side stand down, rode into city traffic, and tried to turn left.  I know it's not likely, but the switch is there for more than avoiding lurching forward when starting.

[MikeW]

An update on the cutting out issue.

I replaced the side stand switch and everything looked good for a few weeks until the bike started faulting again.

Two weeks ago the cutting out got so bad my wife didn't want to ride it anymore. The bike even faulted for me while idling which was a first.

Anyway to cut a long story short I replaced the logic relays with new aftermarket relays and it hasn't faulted so far.

Hopefully this time I've nailed it.

[Chuck in Indiana]

An update on the cutting out issue.

I replaced the side stand switch and everything looked good for a few weeks until the bike started faulting again.

Two weeks ago the cutting out got so bad my wife didn't want to ride it anymore. The bike even faulted for me while idling which was a first.

Anyway to cut a long story short I replaced the logic relays with new aftermarket relays and it hasn't faulted so far.

Hopefully this time I've nailed it.

Yeah, I was going to mention changing out the relay itself, but you've done it. That's probably it. Might be nothing more than corrosion on the relay base/relay pins. Caig DeOxit is your friend.

[Muzz]

Missed this thread the first time around.

Knew about the side stand and keep that lubed and apply WD40 on a regular basis. The relay is definitely worth noting. Starting from the front, which one is it?

[MikeW]

I believe that the two at the front are the safety interlock relays. I had four relays so I replaced all of them except for the larger middle one which I believe has a diode in it. I gave everything a good clean whilst I was at it.

Our Breva will hit 90,000 ks (56,000 miles) any day now. Never thought I'd see a small block go that far without any major problems. The bike still rides like new.

Mike