Power cutting out, advice wanted please

I’ve had this problem on and off with the bike, and I’m pretty sure it started before I did any work on it.

Sometimes while riding, it just cuts power. Usually happens at wide throttle openings, but sometimes at low speeds too. And at low speeds it will totally stall.

So far I’ve replaced the fuel lines (old ones had a slight kink), replaced the fuel filter, and sprayed de-oxit on every electrical connection (including the ECU ground wire). It feels more like a fuel than electrical issue, but I can’t rule anything out. When it dies there is no warning light on the instrument panel and the tach needle does not drop to zero, so if it’s electrical it’s not a major failure. I ran out of ideas so replaced the coils as well. Haven’t tried riding with the new coils but don’t hold much hope for that (I got coils off a wrecked Cali for $45)

The only pattern I can see for when it happens is that it seems to be after riding for a while. Could be only when it’s warm?

I don’t want to replace the fuel pump unless I’m 100% sure it will fix it, because those suckers are expensive! Around $800 last I checked.

I don’t want to ride it any more, it’s pretty scary when you are passing someone and the engine just cuts. And then when the power comes back on just as suddenly it can be pretty dangerous.

Any ideas? I’m desperate on this, I can’t ride my beautiful GRiSO until it’s fixed.

Side stand switch?

Pete Roper wrote:

Side stand switch?

When it happens, the side stand indicator doesn’t light up on the instrument panel, so I don’t think that could be it.

Sounds fairly similar to what I had and in my case it was caused by damaged spark plug caps/cable, might be worth it to closely inspect those for tearing as its very easy to do and at least you can then rule that out.

But I'm sure one of the experts will be along shortly to tell you what's wrong


edit: I'm too slow at typing

motor-timothy wrote:

Sounds fairly similar to what I had and in my case it was caused by damaged spark plug caps/cable, might be worth it to closely inspect those for tearing as its very easy to do and at least you can then rule that out.

Hmm, I’ve recently replaced the caps (with NGK) but not the cables. Might be worth a try.

Battery terminal lose, internally.

Is it a total power loss or just a sudden drop accompanied by lots of vibration as you open the throttle?

Pete Roper wrote:

Is it a total power loss or just a sudden drop accompanied by lots of vibration as you open the throttle?

It feels like a total power loss, so both cylinders. And when it happens when the bike is not moving fast it actually stalls.

Sounds like it's cutting in and out. Now if the dash doesn't die then it implies something that only effects the ignition. Sidestand switch, neutral switch (?) or phase sensor.

Any codes?

There are no stored codes. And the neutral light or side stand switch light do not come on when it happens.

It seems to happen when I open the throttle, which makes me suspect a fuel issue. On the other hand it cuts in and out very abruptly, which seems more electrical. Very puzzling.

GuZeee wrote:

......
Could be only when it’s warm?
......

The gearbox warms up, so does the 5(?) mm screw that holds the ground wires...

Fuel, methinks. As in, delivery.

Might be worth lifting the tank to see if the main fuel hose is kinked.

ECU ground? It grounds the injectors to fire them, so worth checking.

Have you tried emptying the tank and refilling it with fresh and clean fuel?

It sounds as though the dash is staying alive so you can rule out the ignition switch circuit
What about the kill switch, if you operate that while running does it throw up any alarms that are different?

Consider putting a small lamp on the bars that you can wire to points in the loom to check for power loss
Like Secondary injection relay pin 3 - eliminate losing power to injectors and coils.

The first thing I did was replace the fuel hoses with a brand new part. Then I took out the fuel pump and replaced the fuel filter. There was indeed lots of crud in the bottom of the tank, I cleaned it out the best I could. There are a couple of mesh filters in there too, I wiped those off to clean them.

I’ve gone through two fresh tanks of gas since then. At first it seemed it happened right when the fuel light came on (twice), but that may have been coincidence: this last time I had only gone 45 miles on the fresh tank of fuel when it started cutting out really badly and eventually stalled. After that it started up and worked fine the last few miles home.

I thought it might be the kill switch, and sprayed in some contact cleaner and worked the switch a bunch of times. But the last time it happened, it would kind of run rough at low throttle then cut out completely at larger throttle openings, so it’s not a complete on/off situation.

ECU ground: I already took that off, sprayed with de-oxit, and screwed it back on tight securely.

The power lamp to injection relay might be a good thing to try. Come to think of it, I haven’t had the relays out: maybe I should remove, spray and re-seat them? (I’ve done that with every other connector but not the relays)

I realized (the hard way obviusly) that a power loss at a contact/wire/whatever that powers any component will be sensed by the ECU, and some alarm will appear. Maybe not the correct one, still there is going to be an alarm. Eg, a bad contact ath the main relay, wil triger a coil alarm, or an injector allarm, or....

There is going to be no indication at all, if the loss is at the ground path. There are 3 ground paths, 1 (or 2?) for the ECU and relays, 1 for the battery, 1 for the generator and spark plugs (chasis). Those are connected by the screw that holds the starter cover, can easily crack (or totally snap) messing up the electrics.

An other thing that can couse strange power loss is a crack at the "T" connector that splits the main fuel line to the injectors. Could open up and loose fuel when expanded by the engine heat, could close and stop loosing fuel when contracted chilled by the lost fuel evaporation.

avgpetro wrote:

I realized (the hard way obviusly) that a power loss at a contact/wire/whatever that powers any component will be sensed by the ECU, and some alarm will appear. Maybe not the correct one, still there is going to be an alarm. Eg, a bad contact ath the main relay, wil triger a coil alarm, or an injector allarm, or....

There is going to be no indication at all, if the loss is at the ground path. There are 3 ground paths, 1 (or 2?) for the ECU and relays, 1 for the battery, 1 for the generator and spark plugs (chasis). Those are connected by the screw that holds the starter cover, can easily crack (or totally snap) messing up the electrics.

That's good to know. Although I think if the main ground wire is interrupted, the clock resets, and that's not happening. And I checked the ECU ground already where it connects to the chassis (not however internally inside the ECU case itself, which might be a possibility).

Quote :

Another thing that can couse strange power loss is a crack at the "T" connector that splits the main fuel line to the injectors. Could open up and loose fuel when expanded by the engine heat, could close and stop loosing fuel when contracted chilled by the lost fuel evaporation.

Yeah my first thought was fuel line, and I put in a new part that includes everything from tank to injectors; it had no effect.

I appreciate all these suggestions everyone, please keep them coming! It's got to be something.

I must say you do seem to have the worst luck with your GRiSO Hope it turns out to be something cheap and easily fixed!

I asked about the kill switch, if you operate that while riding does it look the same, lights etc.

You have to start troubleshooting to narrow it down
Points to Monitor while riding, I think in this order, if it still cuts out and the light stays on move to the next or do all 3 at once. I'm trying to single out the points that will go off without an alarm light.
1/ Secondary Injection relay pin 3 - power to injectors, coils
2/ Primary Injection relay pin 87 - power to ECU pin 17, secondary injection relay, kill switch
3/ Kill switch - power to ECU pin 27
A 12V lamp grounded at the bars with a small wire 20/22 gauge long enough to reach under the seat, wrap around a relay pin.

Have a look at the loom where it wraps around the headstock, move the bars back and forth, is there any excessive bending spots, copper work hardens and becomes brittle if it's bending too tightly, this is usually on much older bikes.
If any points seem to bend too much pull hard on the wires, the insulation will stretch and snap if the copper is broken, I think the wires to concentrate on is the loom from the kill switch.

Have you eliminated tank suck, that wouldn't show any alarms either?

Kiwi_Roy wrote:

I asked about the kill switch, if you operate that while riding does it look the same, lights etc.

You have to start troubleshooting to narrow it down
Points to Monitor while riding
Secondary Injection relay pin 3 - power to injectors, coils
Primary Injection relay pin 87 - power to ECU pin 17, secondary injection relay, kill switch
Kill switch.
A 12V lamp grounded at the bars with a small wire 20/22 gauge long enough to reach under the seat, wrap around a relay pin

Have a look at the loom where it wraps around the headstock, move the bars back and forth, is there any excessive bending spots, copper work hardens and becomes brittle if it's bending too tightly, this is usually on much older bikes.
If any points seem to bend too much pull hard on the wires, the insulation will stretch and snap if the copper is broken, I think the wires to concentrate on is the loom from the kill switch.

Have you eliminated tank suck, that wouldn't show any alarms either?

Thanks for those tips, I will check all those things. As for "tank suck", I did clear a plugged breather hose and it didn't make a difference. I never feel any pressure release when I open the fuel cap either. But it does explain the symptoms better than some of the other possibilities... I wonder if there is an easy way to test for that while riding? (I could test if the problem goes away when the fuel cap is not snapped shut, but I don't really want to ride long distances in that state.)

GuZeee wrote:

....Although I think if the main ground wire is interrupted, the clock resets, and that's not happening. And I checked the ECU ground ....

A loose contact of the main ground, at the starter cover screw, can add resistance (voltage drop) to the circuit. The drop may not be sufficient to create any problem to the ECU, that needs minimal power, still, can be enough for other components not getting enough power to operate as supposed to - like the fuel pump. This screw is affected by the heat of the gearbox as it is attached to it, and is too thin - overtigth it and will brake. If you don't want to find some other bolt to connect the grounds, at least make sure that there is a spring washer between the screw and cable connectors - its a washer that when free is bended.

ps, no need to check for power to injectors and coils, the ECU does that, if there is low power at any coil or injector it gives a service alarm and stores the code - ECU error 23 or 25 or 27 or 29.

avgpetro wrote:

A loose contact of the main ground, at the starter cover screw, can add resistance (voltage drop) to the circuit. The drop may not be sufficient to create any problem to the ECU, that needs minimal power, still, can be enough for other components not getting enough power to operate as supposed to - like the fuel pump. This screw is affected by the heat of the gearbox as it is attached to it, and is too thin - overtigth it and will brake. If you don't want to find some other bolt to connect the grounds, at least make sure that there is a spring washer between the screw and cable connectors - its a washer that when free is bended.

ps, no need to check for power to injectors and coils, the ECU does that, if there is low power at any coil or injector it gives a service alarm and stores the code - ECU error 23 or 25 or 27 or 29.

Oooh, this is very interesting indeed! I will definitely check those ground connections and change the bolt and washer. Thanks!

[quote="GuZeee"]

Kiwi_Roy wrote:

I asked about the kill switch, if you operate that while riding does it look the same, lights etc.
As for "tank suck", I did clear a plugged breather hose and it didn't make a difference. I never feel any pressure release when I open the fuel cap either. But it does explain the symptoms better than some of the other possibilities... I wonder if there is an easy way to test for that while riding? (I could test if the problem goes away when the fuel cap is not snapped shut, but I don't really want to ride long distances in that state.)

Do you have a spare key, just crack it open when the symptoms occur