Topic: Engine dies suddenly while riding, and then comes back .... !

[The Lone Builder]

While on a ride on Friday, the engins on my 750K2 just suddenly cut out. As I rolled to a stop, I tried bumping it and it started again and ran normally. This happened several times on the ride with the interval between cutting out and coming back varying between 10 secs and a few minutes - I was coming down a mountain, so just kept rolling.

It had cut out earlier while stopped, but started again after a couple of tries with starter.

Bike is standard apart from Hondaman's ignition and a key saving relay.

My first thought was fuel starvation, and it must be at or above the fuel tap to affect all 4 cylinders. So today I drained the tank and dismantled the fuel tap. I discovered nothing wrong with the tap and the pic shows what came out of the bottom of the tank; not enough I'd have thought to cause the problem.

The only other things I can think of is a faulty relay; a loose connection in the circuit relay / kill switch / coils, or in power supply to  the relay.

I have just thought that as it doesn't splutter and die – it just dies – it sounds more like and electrical problem than a fuel problem.

Anyway, I'm going to go check the wiring, but in the meantime, and thoughts would be appreciated.

Cheers.

[Scootch]

I would suggest taking a look at the ignition switch and see if it is intermittent.  Also look at fuses to make sure the fuse that supplies power to the ignition is intact and not intermittent.  The relay is also another possibility. I had a similar problem in that my 10 Amp fuse and fuseholder was the problem.

[PeWe]

Bad ignition switch can be a cause too.
A 12V connection from battery all the way to the coils.
Loose minus connection too.
If headlight goes off at the same time a general power/ grounding problem.

If only ignition turns off, local in that circuit, kill switch included that might enter kill mode.
The handle bar switches  with wirings to headlight bucket need some maintenance after a few years.

[newday777]

That will clog the jets, float valves and orifices and is from a dirty, rusty tank. It needs to be cleaned out. A little rust in the tank does bad things, just as old gummed gas will.
You have a starvation of fuel.

[70CB750]

When it was happening to me it was a loose connection on the battery.

These instant cut offs are most likely electrical. 

[Don R]

In my case it was the ignition switch, I just learned to find its sweet spot. I only have a soft fob on my bike key chains, the weight of other keys can be an issue. So I've been told.
 Agreed on the rust. I tried living with a rusty gold wing tank, you just can't filter it out. I had two inline filters and swapped the first one often. I could get away with multiple filters because of the fuel pump.
  I recently bought 4 gallons of Evaporust to treat my tanks with, I did the first one with vinegar to get the worst rust out and finished with the Evaporust. My tank looked pretty good with just some rusty spots but the vinegar looked like coffee when it came out. That tank is lovely now.

[The Lone Builder]

Thanks all.

Idiot lights stayed on, so that excludes the ignition switch, doesn't it!

There is only the one 15A fuse, so again idiot lights rule that out.

I've checked and cleaned connections to the coils and all looked OK. Tomorrow I'll go into the headlight bucket and check connectors there. Will also check the battery connections.

Next time out, I'll carry a spare relay

The dirt from the tank only came out when I sloshed some fuel around having already emptied the tank; all that fuel was clean and the filter in the tap was clean. I also have two little in-line filters which maybe could do with being changed as they are now 3-4 years old. The tank was lined with RedKote a few years ago. I'll give it a good clean before refilling it.

I'll keep you updated.

[calj737]

When it was happening to me it was a loose connection on the battery.

These instant cut offs are most likely electrical.

Yup, dead giveaway is prompt restart. Check the ground side of your connections from the battery. They’re the primary culprit

[HondaMan]

With my Transistor Ignition, there is one possible place where trouble could happen: where the Black wire plugs into the Black/White at the coils. Often the old female connectors at those coils are corroded and/or spread and loose, which could make intermittent power to the Ignition box happen.

I only know this because when Terry in Australia had Serial #1 to test and I had #2 on my bike (circa 2005) I discovered that my Black/White socket was cracked where the #1-#4 coil's wire had plugged in, and that was the one I happened to choose to plug in the Ignition's Black power wire. Wiggling the harness near the front of the tank would make the engine stop, but the idiot lights would still show normal power. I eventually replaced the double-socket connector in the bike's harness: let me know if you need one, because I had to buy 5 to get 1 then.

[newday777]

Thanks all.

 I also have two little in-line filters which maybe could do with being changed as they are now 3-4 years old. The tank was lined with RedKote a few years ago. I'll give it a good clean before refilling it.

I'll keep you updated.

Is your fuel line and are these filters down below the fuel inlet tee level of the carbs??? If so that will cause starvation of the gravity feed fuel flow.

[PeWe]

Or fuel cap on tank has clogged air vent.
When it dies, open fuel cap help it to start direct?

[rotortiller]

A dirty kill switch can do that (as can other things mentioned-key switch and fuse holder), they come apart carefully and the contacts can be cleaned.

[BenelliSEI]

Check that fuse. Flick both ends with a finger. Make sure one end of the filament isn’t loose and making intermittent contact.

[PeWe]

The root cause will be interesting. This kind of problem can happen us all.

Not fun when engine stop without warning.

[The Lone Builder]

Well I checked most things suggested - didn't dismantle the kill switch, but I did tighten up a couple of connectors.

All looked good until I checked the connection and the battery -ve terminal; this was loose! It was loose, but still attached by the screw, so I'm not sure if this is really the cause of the problem; surely if that were the cause there would be no electrics at all.

When draining the tank I thought of the fuel cap vent, but opening the cap made no difference to the flow. The filters are above the carb inlets.

Well having found one fault, I guess the proof will be in the pudding!

Ride out tomorrow.

[jgger]

My money says you found it. Intermittent or weak connection can do that, enough juice to run the idiot lights but not enough to run the important electrics.

[Deltarider]

You've found it. 100%

[The Lone Builder]

It would be nice to report that that was the end of the issue, however ...

I put everything back together and added some fuel to the tank - about 4 litres to be exact. This was 95 Octane I had bought a few weeks ago.

Pushed the started and she fired up straight away  . Closed the choke and she died  . Tried again with the same result. And again, and again. SH1t, I thought, that fuel must be bad. And then maybe its because its 95; normally I use 98E10, but last time I refilled - before the problem started - I had to use 95 (E5 I think). Maybe that contributed to the problem. Nooo, 95 is fine.

Anyway, I decided to drain the tank and go get some fresh 98 octane. I opened the petcock and only a dribble of fuel came out; opened the reserve and fuel flowed freely from both tubes. Back to main and flow ceased .... 💡💡 Ka-ching!

Of course, with only 4 litres in the tank its on reserve!! Tank back on, fuel tap opened on reserve and vroom! Ever feel like a clown?

Anyway the good news is I added some fresh 98 stuff and had a short ride without an issue.

So that, hopefully, is that sorted; now the next issue ... but that's for another post I think.

Thanks for all your suggestions.

[Shtonecb500]

 was riding to chicago from detroit and my bike was experiencing complete powerless on hard bumps, at the toll road i checked and had a broken red wire to my solenoid and had to twist ends together to limp into chicago. Check all electrical components....when it was happening i thought it was mechanical failure.

[MauiK3]

Not a motorcycle but I once had a battery positive cable corrode back up under the insulation at the terminal. It could not be seen at all. Took me a bit to figure it out.

[PeWe]

Good thread with engine stopping ideas we all can suddenly get

[smee]

It would be nice to report that that was the end of the issue, however ...

I put everything back together and added some fuel to the tank - about 4 litres to be exact. This was 95 Octane I had bought a few weeks ago.

Pushed the started and she fired up straight away  . Closed the choke and she died  . Tried again with the same result. And again, and again. SH1t, I thought, that fuel must be bad. And then maybe its because its 95; normally I use 98E10, but last time I refilled - before the problem started - I had to use 95 (E5 I think). Maybe that contributed to the problem. Nooo, 95 is fine.

Anyway, I decided to drain the tank and go get some fresh 98 octane. I opened the petcock and only a dribble of fuel came out; opened the reserve and fuel flowed freely from both tubes. Back to main and flow ceased .... 💡💡 Ka-ching!

Of course, with only 4 litres in the tank its on reserve!! Tank back on, fuel tap opened on reserve and vroom! Ever feel like a clown?

Anyway the good news is I added some fresh 98 stuff and had a short ride without an issue.

So that, hopefully, is that sorted; now the next issue ... but that's for another post I think.

Thanks for all your suggestions.

Just commenting to say I have had this exact problem on a different bike I had years ago. Didn't think about checking petcock until the very end... ran it on reserve for years and just counted my miles. Gasket material sloughed off and was blocking the hole... ha figures

[70CB750]

My K0 had no reserve till I replaced the petcock with aftermarket.

[newday777]

It would be nice to report that that was the end of the issue, however ...

I put everything back together and added some fuel to the tank - about 4 litres to be exact. This was 95 Octane I had bought a few weeks ago.

Pushed the started and she fired up straight away  . Closed the choke and she died  . Tried again with the same result. And again, and again. SH1t, I thought, that fuel must be bad. And then maybe its because its 95; normally I use 98E10, but last time I refilled - before the problem started - I had to use 95 (E5 I think). Maybe that contributed to the problem. Nooo, 95 is fine.

Anyway, I decided to drain the tank and go get some fresh 98 octane. I opened the petcock and only a dribble of fuel came out; opened the reserve and fuel flowed freely from both tubes. Back to main and flow ceased .... 💡💡 Ka-ching!

Of course, with only 4 litres in the tank its on reserve!! Tank back on, fuel tap opened on reserve and vroom! Ever feel like a clown?

Anyway the good news is I added some fresh 98 stuff and had a short ride without an issue.

So that, hopefully, is that sorted; now the next issue ... but that's for another post I think.

Thanks for all your suggestions.

Sean
Any further updates? It's been 7 months since you last posted on this problem and wondering if you have had any longer rides since to see if it is corrected. I'm aware of the upcoming trip across the pond and of your having doing open heart surgery on the motor so just wondering 🤔......

[MauiK3]

Maybe a plugged fuel cap vent?

[Tracksnblades1]

I’ll go out on the branch…

After reading his posts, I’m guessing he has two problems.
The obvious pet cock, reserve only functioning.

But with a clean instantaneous all four cylinder cut off it’s an electrical gremlin at work…

Other than a full instant on choke situation, I’ve never had an engine not display some type of carburetor mixture problem before instantly dropping all cylinders simultaneously. At least a burble or a hesitation before nothing on all cylinders. On my old 76f even forgetting to turn the gas on will result in a cylinder or 2 to start acting up due to low float bowl level prior to lights out on all cylinders…? I just can’t picture all four carbs fuel bowls all running out of fuel at the exact same time..especially if it been on its kick stand for any period of timd….If so, I want that guy to set my floats for me…😁