GRiSO Startus Interuptus

I thought I would investigate the new to me 2007 GRiSO to see if it would benefit from the Startus Interuptus fix.
As you probably know the ailment is caused by wiring that is not able to deliver the current the starter solenoid would like.
The solenoid if its allowed to will draw over 40 Amps literally throwing the cog's into mesh with a resounding clunk.
Unfortunately due to an oversight at the factory the wiring is not up to the task. it usually finds a weak spot, Ignition switch, relay base or weak wire along the way which effectively throttles the current I used to think the main culprit was the ignition switch however today I discovered the tiny wire on the GRiSO from the Start Relay to the solenoid, I doubt they could have found a smaller wire if they tried.
I did a test on the wire to see how much Voltage it would lose at 40 Amps, it calculated out that it would drop 1.8 Volts
Add to this the resistance of the supply, relay contacts/relay base and it soon adds up.

Next step is to take some measurements to determine how the starter is working, I did some time and current measurements using an oscilloscope.
When you press the start button a heavy current pulse from the start relay pulls the solenoid into the core engaging the gears. The heavy current pulse lasts until the main contacts close.
At this point the battery Voltage is applied to the motor and it draws well over 150 Amps, the motor starts to turn and the solenoid current drops to about 10 Amps.

I measure this time and I find the solenoid pulse lasts for 50 milliseconds while the solenoid current peaks about 22 Amps which is ok but not great.

So then I upgrade the wire from the relay to the solenoid. The current pulse now lasts only about 15 milliseconds, less than 1/3 as long telling me the solenoid is operating at three times the speed it was before and the current peaks just over 30 Amps

Note: This current I am referring to is not the cranking current, it's just the current into the solenoid.

I have a storage scope but it's quicker just to sketch out the trace. I drew Before and After on top of each other for comparison.
You can see what a huge difference it made when I replaced Luigi's little bitty wire (Red Trace) with an 18 gauge wire (Green Trace)

Interestingly after the fix although the current is much higher the solenoid expends less than half the energy it did before

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Let me say again, this is not the starter motor current, it's just the current going to the solenoid coils.
It stands to reason a faster solenoid is less likely to hang up giving you the dreaded click.

BTW the faster 30 Amp (green trace) uses less than half the energy to engage the gears (Amps x time)

Its worth doing, i spent a lot of time on holiday last year hitting the start button and getting nothing. There is a kit you can buy, but with a couple of connectors you can wire up your own solution.

Regarding “Startus Interuptus”
I was inspecting the spade connector to the starter solenoid . The female connector appears to have been anealled as it quite soft and only requires the lightest finger touch to slide it off.
Has anyone narrowed the starting issue with the quality of connection at the starter solenoid spade connector?

The contact is important, chances are it was annealed because it was getting hot.
Were you having trouble with it not cranking?

Thanks Roy.
If you search Startus Interuptus, there has been many threads on this topic .
Quite a few different fixes from changing to a higher amp fuse to a wiring loom mod.
I have changed my fuse once as I carry a spare set with the bike.
Upon first inspection of the electrical system earthing and contacts etc.
I found the spade connector had gone soft. I wondered if this is the cause for this problem as it’s an easy fix.
I swaged in a new spade connector that is normally connected to an oven heating element. Covered it in black heat shrink . Hoping my mod will prevent future issues.

Yes, i have been involved in quite few Startus Interuptus fixes on other models, quite often the ignition switch is the weak point, the grease goes hard making the contacts higher resistance and the leads are also quite small.  I'm not familiar with the switches like these CARC ones, I suspect the wires are more direct since they don't move with the steering.
i think the biggest improvement you can make on the GRiSO 1100 is a larger wire from the relay to the solenoid, note how mine went from 20 to 30 Amps, with a huge boost in speed.
I believe my new wire is 18 AWG, the original looked like 20 or smaller.
A 20 Amp fuse is appropriate for the 30 Amp inrush.
Update March 20 2020: The 1200 GRiSO definitely needs a rewire of the start relay supply as detailed in Martin's video on page 3

The wiring diagrams don't show how the solenoids are actually wired otherwise Luigi might figure it out, there are two coils not one as the schematics show. I will post the starter schematics when I figure out how to post a file.

Note: I measure the current and speed with an Oscilloscope.

Kiwi_Roy wrote:

.....i think the biggest improvement you can make on the GRiSO is a larger wire from the relay to the solenoid.....
.......
.... I believe my new wire is 18 AWG, the original looked like 20 or smaller.....

I think it was "Occurunner" that posted, long time ago, about a fix mentined in some official seminal notes (I would realy like to have those notes)
The fix was to isolate at both ends the existing wire that runs from the relay to the solenoid, and run a new 2,5mm^2 wire (so no need to open the loom)
2,5mm^2 is 13 AWG?

I believe the same issue exists with all the "high" current wires - from the generator to the fuse, to the battery, to the other fuse, to the relay, to the solenoid...

That's good Petros, here's the reason.
If you were to take a meter and measure the current in that wire you would see just under 10 Amps, that's because the meter is far too slow to show what's really going on.
There are two coils in the solenoid, one measures 1.05 Ohms the other only 0.25 Ohms
By Ohms Law the current they draw
12/1.05 =11.4 Amps
12/0.25 =48 Amps, it's this one Luigi didn't allow for.
The high current coil is the one that does the lions share of the work engaging the starter, the magnetic field it produces is 3 times as strong as the 11 Amp coil.
As soon as the main contacts close in 30-60 milliseconds the current in the high current coil drops to zero and the low current coil holds the gear in place.

The high current coil is also the one that can cause the fuse to blow, if its turned on too long or the field is just a little too weak to pull the gear in but maybe half strength, say 25 Amps total the fuse will pop.

To summarise, if you have an early 1100 GRiSO
Replace the tiny wire from the relay to the solenoid with at least 1mm or 18 AWG, this will double the speed the starter engages and make it more reliable.
This model has a direct feed to the relay (not through the ignition switch)

If you have a 1200 8 Valve
The wiring on this starter is quite different, for one thing the start relay is fed through the ignition switch, this has been the downfall of many other models.

wardest wrote:

I found the spade connector had gone soft. I wondered if this is the cause for this problem as it’s an easy fix.
I swaged in a new spade connector that is normally connected to an oven heating element. Covered it in black heat shrink . Hoping my mod will prevent future issues.

Did this do the trick? My Startus Interruptus is playing up again, and I noticed the spade connector is very loose on mine as well and the contacts have turned a dull grey.

Motor-Timothy
Without tempting fate. I haven’t had any more fuses fail since doing the mod.

Roy.
A picture is a 1000 words.
Where does the Starter relay live , The Start up maintenance relay etc. if you can as it would be great help time poor none garage owning types

motor-timothy wrote:

wardest wrote:

I found the spade connector had gone soft. I wondered if this is the cause for this problem as it’s an easy fix.
I swaged in a new spade connector that is normally connected to an oven heating element. Covered it in black heat shrink . Hoping my mod will prevent future issues.

Did this do the trick? My Startus Interruptus is playing up again, and I noticed the spade connector is very loose on mine as well and the contacts have turned a dull grey.

The connection there is obviously bad, get another spade connector and a beefier wire say #14 and replace the wire all the way from starter solenoid to the relay socket.
If you don't want to replace the connector in the socket cut the wire off a few inches away and crimp the larger one to it.
Note how on my bike the larger wire doubled the speed the solenoid engaged.
I always apply some Vaseline to those sort of connectors where it might get wet. Keep the water out and its unlikely to corrode.

wardest wrote:

Motor-Timothy
Without tempting fate. I haven’t had any more fuses fail since doing the mod.

Roy.
A picture is a 1000 words.
Where does the Starter relay live , The Start up maintenance relay etc. if you can as it would be great help time poor none garage owning types

On the 1100 its under the RH side of the seat surround, it looks very difficult to access but its not so bad, just take the 3 screws out of the RH side then you can slip the rubber surround off the bracket or remove 2 more screws and all 4 relays will come out c/w bracket
The front most relay is the start.
There are two small wires going to the silver relay pins, they are the coil, leave those alone
Theres a medium size green wire going to a copper pin. that's 12 Volts leave that alone
A tiny reddish coloured wire going to the other copper pin. that's the one to the solenoid but Ohm it out with your meter to be sure.
It will read zero on your meter but trust me the resistance is too high, cut that a few inches from the relay and splice on a beefier wire to the solenoid.

Beetle says the 1200 relays are in the same location
I wonder if they skimped on that wire also?

Same location.

I replaced the spade connector today but unfortunately didn't help. It still usually clicks on the first attempt to start, then fires up fine on the second attempt. Occasionally it clicks then fires up anyway, very odd

motor-timothy,
                     This sounds like classic Startus Interuptus, on Breva and Norge models, the usual fix is to snip the yellow wire feeding the Start relay and power it direct from a fuse at the battery.
In this case you would snip it South of the joint between Start and Startup Maintenance relays.

The 8V valve engine runs the power through the ignition switch.

A couple of things you can try
Crimp a spade connector on a length of 18 gauge or larger wire, slide it onto the solenoid connector, make sure the bike is in Neutral then try touching it to the battery +, if you can get the bike to crank over 20 or 30 separate times (leave the key Off) then you can be certain that the starter and solenoid are in good condition.

Is the existing wire between the relay and solenoid at least 18 gauge, it should be, my 1100 had a wire far too tiny for the job.

Next thing you can do is monitor the Voltage at the Start relay Yellow wire with a small lamp, it should glow brightly when you turn the key on and stay bright when you press start. if it goes dim when the engine refuses to crank there is the problem either flat battery or high resistance in the switch or wiring to and fro
[You must be registered and logged in to see this link.] Fuse 2 at (22) is a convenient place to connect the lamp, there and chassis.

What is the history of your battery?

Note: I have never personally done this fix on an 8V GRiSO, i'm not certain what effect it has on the start maintenance relay. Hopefully another owner will pipe up.
Worst case the starter would latch on until you pull the new fuse.

Either do above or pull the ignition switch apart and clean it every 5 years, lube the switch with Vaseline aka Petroleum Jelly.

When I was testing the wiring on my 1100 I pulled the two rear most relays to disable the ECU so I could crank the bike without it actually firing.

When I first bought my 2001 VII Sport I started hearing about Startus Interuptus so I decided to investigate what caused it. It turns out that the Valeo Starter and it's predecessor the Bosch starter have a double coil in the solenoid. At the instant the starter button is pressed and the start relay closes the two coils combined would pull about 50 Amps, they don't of course because the bike wiring is unable to supply it, there's too much Voltage drop. Not one Moto Guzzi schematic shows this high current coil, I have to assume they don't know about it or they would fix the problem.

Note: This schematic is not drawn from a GRiSO but (VII Sport) the principle is the same
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Note the current waveforms I drew at the bottom of the page. These were drawn with the aid if an Oscilloscope
The early VII Sport was wired (as per the red dashed line) the current inrush was almost 50 Amps.
My GRiSO started out at just 22 Amps but I boosted it up to 30 with just a simple wire upgrade.
Read my Note: 1 about putting the wiring through the switch (as per the later Grisos)

Kiwi_Roy wrote:

To summarise, if you have an early 1100 GRiSO.  This model has a direct feed to the relay (not through the ignition switch)

Not originally, it must have been already modded before you purchased it.

kiwi dave wrote:

Kiwi_Roy wrote:

To summarise, if you have an early 1100 GRiSO.  This model has a direct feed to the relay (not through the ignition switch)

Not originally, it must have been already modded before you purchased it.

Sorry Dave
Here is the 2006 Start Relay fed direct from fuse "C" (strictly speaking through 2 fuses in series)
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And the 2008 downstream of the ignition switch from fuse 2
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I would hazard a guess and say the later one will have more problems.
But I recommend beefing up the wire on the early ones, it's a no brainer.

The modern schematics don't even show one coil for the starter solenoid, how's an owner supposed to figure that out?

This is how the starter solenoid should be drawn, with two coils. (The names or the coils are mine but I have started calling the pull in coil the Grunt coil, I think its more descriptive)
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The two coils work together to pull in the solenoid
The Holding coil pulls about 10 Amps
The Pull In coil would pull over 30 Amps if it had decent wiring.
(but instead they only pull about 22 Amps combined through the wimpy wires)
When the main Contact closes the Pull In coil now has the same Voltage at both ends so it's current drops to zero and the Hold In coil keeps everything in place with
it's 10 Amps and the bike starts to crank as the motor receives the full current from the battery.

These are the currents I measured and show in the red trace of post No 1

When you take your finger off the button the spade connector (blue wire) no longer has Voltage and the current runs backwards through the two coils in series but now the coils work against each other cancelling the magnetic attraction letting the solenoid spring back open.

Note:
The large dot at the top of the coils is to show that when fed with the same polarity they work together.

It sounds like a lot going on doesn't it? I tried to keep it simple

Kiwi_Roy wrote:

If you don't want to replace the connector in the socket cut the wire off a few inches away and crimp the larger one to it.

We have a startus interruptus problem on a 1200 Sport 8V and I wonder if it makes sense to cut the thinner wire and crimp a thicker on it. IMHO; the small rest of the thin wire will work as a resistance and you won´t get higher voltage at the solenoid.

What do you think?

Best regards
Georgios

If the thicker wire is half the resistance of the thin one & you replace 95% of the length; then you'll reduce the resistance by 95%......& your voltage drop will be proportionately less at any given current

Ohm´s law?

O.k., thank you.

Yes replace the wire but on your model you are probably losing most across the ignition switch and the wire to and fro.
Better to snip the yellow wire feeding the relay and feed it direct from a new fuse at the battery, that's the usual fix.

paulbrice wrote:

If the thicker wire is half the resistance of the thin one & you replace 95% of the length; then you'll reduce the resistance by 95%......& your voltage drop will be proportionately less at any given current

I didn't agree with your logic, but I didn't at first know why.

Now, let's see, if you replaced 100% of the wire with one with half the resistance, you would reduce the resistance and therefore your voltage by 50%. So surely the resistance reduction for 95% replqcement is going to be less than 50%?

Explain please how it gets to 95% reduction and why my logic is flawed.  

Dave, I normally would try, but it's Friday and my head hurts. Beer O'clock real soon; 2 days off; forget about the rest of it till next week.

On a side note my old man is 95 today. We have a piss up tomorrow starting lunch time - could get messy.