Author Topic: Cuts out when accelerating  (Read 7905 times)

Offline 1Sourdough

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Cuts out when accelerating
« on: May 01, 2015, 12:52:03 AM »
A few weeks ago I asked about a condition in which the Strada's engine seems to switch off for half a second or so when accelerating.  At that time someone asked whether it backfired and I answered "No".  It seemed to have been resolved, so I haven't checked for awhile, and now cannot find the thread to see if anyone else has commented.

That response was when it had cut and come back on under hormal acceleration.  This week I found out the engine does backfire quite loudly through the exhaust when the cutout occurs under strong acceleration.  The condition is more pronounced before the engine has warmed completely.

What I thought had resolved the matter was a loose connection.  When I tightened it, the cutting out seemed to go away for a few days.  Then a couple of weeks ago the machine suddenly became quite hard to start from cold.  It pretty much required flooding it and opening the throttles all the way for a minute or two for the fuel to evaporate.  Then it would start with a 10 second or so crank.  I pulled the timing sensor and cleaned a quantity of metal shavings off it.  No, still stumbles.  Replaced the sparkplugs and it starts right up now.

In case it might be the fuel petcock screen was covered with some sort of gunk I ran with the other side. That seemed to work for awhile, then the condition came back with gusto.  Sometimes when running at steady speed the engine begins to run poorly, almost as though running out of gas and running on one cylinder.  Rolling the throttle open stops that, then it begins to cut out and come back on with a backfire. 

Any thoughts?  Oh, this motorcycle has the Digiplex ignition.
1993 Strada 1000, 1996 R1100RT, 1999 V11 EV
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Re: Cuts out when accelerating
« Reply #1 on: May 01, 2015, 03:45:36 AM »
I'm new to guzzi but I assume your bike has carbys?
So from what your describing it sounds like the carbs need a good clean jets blocked, Also you could have water in the fuel tank and the carbs.
If its water you could try a cup full of methylated spirits in your fuel tank.

Offline Chuck in Indiana

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Re: Cuts out when accelerating
« Reply #2 on: May 01, 2015, 05:56:37 AM »
Well, normally I say carb problems are generally ignition, but you probably cured the ignition issue. As mentioned above, I'd pull both petcocks, check the screens, drain the tank and clean the carbs. It could very well be water.
Chuck in (Elwood) Indiana/sometimes SoCal

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Online Kiwi_Roy

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Re: Cuts out when accelerating
« Reply #3 on: May 01, 2015, 06:23:34 AM »
Do both cylinders cut out or just one?
Pull the plug caps and measure from the cap to chassis, both sides should read the same within a % or two.
Here's my thought
If you have a gap in the spark lead or a leak to ground when you open the throttle introducing more air it becomes harder for the spark to jump the plug gap so it either doesn't or finds an easier path to ground,
My 98EV was showing symptoms similar to what you describe, I found it had been fitted with carbon core resistor wire as well as resistor caps, and there was quite a gap in the wire to one cylinder One plug cap to ground measured 8K the other was open circuit.

Is the Digiplex ignition the one with two separate ignition modules?
http://www.thisoldtractor.com/guzzi007/schematics/1994_Strada_1000_Type_1.gif
The one with a single module?
http://www.thisoldtractor.com/guzzi007/schematics/1994_Strada_1000_Type_2.gif
or this one?
http://www.thisoldtractor.com/guzzi007/schematics/1989_750_Strada.gif

Either way to assure yourself it's not a loose electrical connection wire a small lamp to the coil supply
« Last Edit: May 02, 2015, 05:22:45 AM by Kiwi_Roy »
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Offline Aaron D.

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Re: Cuts out when accelerating
« Reply #4 on: May 01, 2015, 06:28:22 AM »
I say go through the connections, especially grounds for the ECU and coils. I doubt very much you have a carb blockage.

56Pan

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Re: Cuts out when accelerating
« Reply #5 on: May 01, 2015, 09:20:02 AM »
(snipped)
  I pulled the timing sensor and cleaned a quantity of metal shavings off it. 
(snipped)

I'm not familiar with the machine at all.  But this would really concern me.  What am I missing here?

Offline acogoff

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Re: Cuts out when accelerating
« Reply #6 on: May 01, 2015, 09:44:38 AM »
     And check for intake leaks between carb and head with some type of flameable spray - WD----staring fluid-- whatever- takes but a second.
« Last Edit: May 01, 2015, 09:45:48 AM by acogoff »
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Offline fotoguzzi

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Re: Cuts out when accelerating
« Reply #7 on: May 01, 2015, 09:48:14 AM »
I'm not familiar with the machine at all.  But this would really concern me.  What am I missing here?
Swarf, kinda normal.. shavings from the ring gear.
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Offline blackcat

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Re: Cuts out when accelerating
« Reply #8 on: May 01, 2015, 09:51:39 AM »
I'm not familiar with the machine at all.  But this would really concern me.  What am I missing here?

Every once in awhile I pull the sensor on my 1000S and there is some metal shavings on there but it never seems to have had any effect on the engine. I guess if it was really loaded up, but that points to another problem.
« Last Edit: May 01, 2015, 09:54:01 AM by blackcat »
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Offline Chuck in Indiana

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Re: Cuts out when accelerating
« Reply #9 on: May 01, 2015, 10:10:09 AM »
I say go through the connections, especially grounds for the ECU and coils. I doubt very much you have a carb blockage.

Oh, I agree about going through the connections. Doesn't take but a few minutes, and never hurts. But he said he'd cleaned the sensor, put in plugs, and it starts right up.
Quote
In case it might be the fuel petcock screen was covered with some sort of gunk I ran with the other side. That seemed to work for awhile, then the condition came back with gusto.  Sometimes when running at steady speed the engine begins to run poorly, almost as though running out of gas and running on one cylinder.  Rolling the throttle open stops that, then it begins to cut out and come back on with a backfire. 

That still sounds like it "could" be water in the tank. There's a reason that aircraft carbs have a drain on the carb, and it is on the list at annual inspection to drain the carb. Water will just sit in the float bowl, and cause a confounding miss.. enough water will kill the engine. I've seen that, too.
That said, "carburation problems are generally ignition."  ;D I've said it before..
Chuck in (Elwood) Indiana/sometimes SoCal

02 Scura RC
87 AeroLario
79 G5
95 Skorpion tour
 
I think senility is going to be a fairly smooth transition for me..

Offline blackcat

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Re: Cuts out when accelerating
« Reply #10 on: May 01, 2015, 10:32:18 AM »
If it turns out to be the Digiplex there is someplace in Germany? who will rebuild the box. I may have the link somewhere but I'm sure a search engine will find them.
boom shakalaka
http://youtu.be/wHUP527txeg

1968 Norton Fastback
1976 Lemans
1981 CX-100
1993 1000S
1997 Daytona RS
2007 Red Norge

56Pan

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Re: Cuts out when accelerating
« Reply #11 on: May 01, 2015, 12:48:36 PM »
Swarf, kinda normal.. shavings from the ring gear.

Yeah, another member here cleared it up for me.  I was assuming a different location for the sensor.  Crankcase.

Offline redrider90

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Re: Cuts out when accelerating
« Reply #12 on: May 01, 2015, 12:50:06 PM »
No reason to not drain the tank and drain the carb bowls but this does not sound like water to me.
This sounds electrical/ignition.
I have had this  problem occur with the now infamous Motoplat as well as with a bad coil and as well as with Dyna III box. If you loose spark and regain it I would expect it to be loud with it fires off. Seems with water it would be acting up all the time. But shoot draining fuel and the float bowls is the easiest thing to do first.
« Last Edit: May 01, 2015, 01:08:59 PM by redrider90 »
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Offline Aaron D.

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Re: Cuts out when accelerating
« Reply #13 on: May 01, 2015, 03:54:36 PM »
I've seen exactly these symptoms from bad coil grounding and even bad tach connectors. The bike works fine at start and low load, then goes wonky when under load.

Offline 1Sourdough

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Re: Cuts out when accelerating
« Reply #14 on: May 01, 2015, 04:15:37 PM »
At first mention of this situation it seemed it was possibly only one cylinder but now it's obvious both are quitting.  It's just the same as flicking the emergency stop switch for half a second, including the loud backfire.

I'll take time this weekend to remove the tank and more carefully examine the wiring.  I only checked the parts mentioned in the first post, thinking that would clear the electrics.  The gas tank was nearly emptied and refilled yesterday, so I'll not drain it until satisfied with the electrics.  By then it ought to be about empty again!
1993 Strada 1000, 1996 R1100RT, 1999 V11 EV
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Online Kiwi_Roy

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Re: Cuts out when accelerating
« Reply #15 on: May 01, 2015, 04:23:55 PM »
At first mention of this situation it seemed it was possibly only one cylinder but now it's obvious both are quitting.  It's just the same as flicking the emergency stop switch for half a second, including the loud backfire.
 
"Either way to assure yourself it's not a loose electrical connection wire a small lamp to the coil supply"

So my little lamp would go out for a second, just saying
72 Eldorado
07 Griso 1100
17 V7iii Special

Moto Guzzi - making electricians out of riders since 1921

Offline Chuck in Indiana

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Re: Cuts out when accelerating
« Reply #16 on: May 01, 2015, 04:40:30 PM »
At first mention of this situation it seemed it was possibly only one cylinder but now it's obvious both are quitting.  It's just the same as flicking the emergency stop switch for half a second, including the loud backfire.

I'll take time this weekend to remove the tank and more carefully examine the wiring.  I only checked the parts mentioned in the first post, thinking that would clear the electrics.  The gas tank was nearly emptied and refilled yesterday, so I'll not drain it until satisfied with the electrics.  By then it ought to be about empty again!

Ok, Fred.. let's talk about this. If you are satisfied that ignition is the problem, (both are quitting) here is what I would do.
(1) It's not likely to be the Digiplex unit. It's a simple solid state switching device. Guzziology says they are pretty bullet proof, and I've never heard of a failure.
So, where does the Digiplex get it's power? Hmmm..
(2) The ignition switch is getting pretty old. It's not uncommon for the grease to harden, and get intermittent contact. It's easy to disassemble, clean, and apply fresh Vaseline. I documented that in the Lario Rehab thread.
(3) From the ignition switch, power goes through the kill switch. It wouldn't hurt to check it out and spray some De Oxit on it, cycle it a few times.
(4) From the kill switch, power goes to the sidestand relay. Even though there's no sidestand switch, there's a relay. This is a likely culprit. The relay itself is very robust, and unlikely to fail, but like any relay, it's pins could be corroded and giving a bad connection. It's the aft one in the stack. Pull it out, spritz De Oxit on the contacts, put it back in, wiggle it around to make sure it has good contact. Also.. *Make sure the ground on this relay base is properly grounded.* Originally, it was grounded to the low fuel light sensor. Many have removed that sensor. Check that ground. So now, we have power to that relay, and all is well. Once it is triggered by the kill switch, it sends power to the relay up by the fuse box.
(5) Have a look at that relay. It is a DPDT, and powers two circuits, the coils on one, and the Digiplex unit on the other. This is a robust (expensive) relay, too.. and is also unlike to fail, but it certainly can have corroded connections. Clean those up as before, spray with DeOxit, and your problems are probably over.
report back.  ;D
Chuck in (Elwood) Indiana/sometimes SoCal

02 Scura RC
87 AeroLario
79 G5
95 Skorpion tour
 
I think senility is going to be a fairly smooth transition for me..

Offline rodekyll

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Re: Cuts out when accelerating
« Reply #17 on: May 01, 2015, 05:50:13 PM »
I'm getting that this is a carbbed bike with an electronic ignition that uses a position sensor.  If I'm wrong, tell me -- I can take it.

I'm thinking that there's a problem with the transition from idle to intermediate jets -- a lean gap between the two.  In a car this gap is filled by the accelerator pump. which dumps raw fuel in the airstream to compensate for the sudden inrush of dry air.  Some guzzi carbs also have accel pumps.  If yours does, I'd check the function.  I'd also clean out the jets.  They may look 'clean', that is, uniformly round as you peer through the jet bore, but they can have a buildup of 'plaque' on the bore surface that effectively changes the aperture size.  So judicious use of a jet drill would be in order.

Again, if this doesn't apply, nevermind.  I have a wiring harness to build.

Offline Chuck in Indiana

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Re: Cuts out when accelerating
« Reply #18 on: May 01, 2015, 06:06:13 PM »
I'm getting that this is a carbbed bike with an electronic ignition that uses a position sensor.  If I'm wrong, tell me -- I can take it.

I'm thinking that there's a problem with the transition from idle to intermediate jets -- a lean gap between the two.  In a car this gap is filled by the accelerator pump. which dumps raw fuel in the airstream to compensate for the sudden inrush of dry air.  Some guzzi carbs also have accel pumps.  If yours does, I'd check the function.  I'd also clean out the jets.  They may look 'clean', that is, uniformly round as you peer through the jet bore, but they can have a buildup of 'plaque' on the bore surface that effectively changes the aperture size.  So judicious use of a jet drill would be in order.

Again, if this doesn't apply, nevermind.  I have a wiring harness to build.

Yeah, that's what it is. 36mm pumper carbs. If it's not water in the carbs, I'm betting on corrosion on the switch/relay bases.
Chuck in (Elwood) Indiana/sometimes SoCal

02 Scura RC
87 AeroLario
79 G5
95 Skorpion tour
 
I think senility is going to be a fairly smooth transition for me..

Offline 1Sourdough

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Re: Cuts out when accelerating
« Reply #19 on: May 01, 2015, 11:24:26 PM »
I'll not get my nap Saturday afternoon; I have a hobby for the weekend.  Will let you know what I find.

Thanks for the good words!
1993 Strada 1000, 1996 R1100RT, 1999 V11 EV
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Online voncrump

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Re: Cuts out when accelerating
« Reply #20 on: May 02, 2015, 03:13:11 AM »
I have had similar symptoms on my 96 1100 carb sport. The first time it happened I found loose battery terminals.
Later on I had a random cutting out of the engine, just a brief cutout followed by a loud backfire. I went for a ride and when the problem started to show I shuffled the relays and the trouble disappeared. Fit a new set of relays and try it.
Good luck, cheers, voncrump
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Online Kiwi_Roy

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Re: Cuts out when accelerating
« Reply #21 on: May 02, 2015, 05:26:21 AM »
The other day when I wrote reply No 3 the site hosting Carl Allison's drawings was down
I found Three different Strada drawings there all different, there may be others.
Is the Digiplex ignition the one with two separate ignition modules?
http://www.thisoldtractor.com/guzzi007/schematics/1994_Strada_1000_Type_1.gif
The one with a single module?
http://www.thisoldtractor.com/guzzi007/schematics/1994_Strada_1000_Type_2.gif
or this one?
http://www.thisoldtractor.com/guzzi007/schematics/1989_750_Strada.gif

The first two drawings show a Stand Relay, are you still using that or has it been disconnected over the years?
If you are not using it I suggest making your wiring more reliable by removing the relay and crimping the two contact wires together.

It's over twenty years since Luigi put your bike together, disconnect the battery and go over all the connections, I'm sure you will find more than a few loose or corroded.
If you have the old style pointy fuses remove each one and polish the ends by rubbing them on your pants  :wife: a cloth then apply a little Vaseline before putting back after bending the clips to apply more tension. It was suggested to me to stretch an "O" ring over the clips, sounds like a good idea!
Pull all of the spade connectors apart one at a time check for corrosion and tightness, squeeze them gently if they are loose
Clean the ignition switch and apply Vaseline.

When I'm working on electrics around the bike I always have a tube of Vaseline handy, I dip wires in it before I crimp them, apply it to spade connectors, smear it on switch contacts and sliding parts, slather it on battery terminals and any other metal to metal electrical joints.
It's a bad habit I've gotten into over the last 50 years ???
« Last Edit: May 02, 2015, 06:18:29 AM by Kiwi_Roy »
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17 V7iii Special

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Offline JoeW

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Re: Cuts out when accelerating
« Reply #22 on: May 02, 2015, 12:03:21 PM »
Most likely cause is a failing coil. I've had the same issue before, if you listen carefully you can tell which side is backfiring. In high school, I'd drop my 65 Buick into low at about 30 mph, turn the key off and then back on and BOOM. It was great until I blew the muffler off. I posted about my coil failure last summer.
http://wildguzzi.com/forum/index.php?topic=71621.msg1113631#msg1113631
« Last Edit: May 02, 2015, 12:06:30 PM by JoeW »
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Offline 1Sourdough

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Re: Cuts out when accelerating
« Reply #23 on: May 04, 2015, 10:43:28 PM »
Most likely cause is a failing coil. I've had the same issue before, if you listen carefully you can tell which side is backfiring. In high school, I'd drop my 65 Buick into low at about 30 mph, turn the key off and then back on and BOOM. It was great until I blew the muffler off. I posted about my coil failure last summer.
http://wildguzzi.com/forum/index.php?topic=71621.msg1113631#msg1113631

Well, I found something of interest, and the remarks here are pretty great, also. 

I was out testing the machine today and found the left petcock seemed to be having trouble passing fuel.  There was less than half a tank of fuel by then so I drained it and pulled the petcock.  The lower portion of the screen around the intake tube was covered by little white flakes!  No rust, just white, paint looking flakes.  Taking a serious look into the tank I saw it appears to have been coated at some time.  Though I could see no sign of rust, the coating is flaking up around the filler.  Not sure that is the only place but it is in trouble right there.  Pulled the other petcock, it also had some flakies around its screen.  Put a little gas back in and sloshed it around to try and remove most of the flakes until figuring how to remove the whole mess.  Put a cup of screws into the tank and spend two months rocking it every night, right? 

Now, Kiwi Roy: This machine has the single Digiplex module and two square, screwed together coils:
   http://www.thisoldtractor.com/guzzi007/schematics/1994_Strada_1000_Type_2.gif

No one in this immediate area carries Deoxit so I bought the brand recommended by the old man in the local parts store.  He said it is what the farmers use on their planters, which sit for 50 weeks of the year and have to work the other two.  While separating plugs to inspect and clean, I got to the coil wires and spoiled the whole day.  I had been happily pulling plugs apart without any problem  When the left coil wire would not separate I took a screwdriver to it and found the latch was strong enough to break the collar on the coil to which it was snapped.  Well, that was the left coil, and it is the left side which has been backfiring, so perhaps it's just as well.  From the info up above it appears the chances are excellent that coil is failing, and ought to be replaced anyhow.  I'll see if MG or Harpers have something in stock.

That's the top of the news, as it looks from here...
 
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