Sudden Flame Out

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Tornado

Tornado

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While out on yet another test ride (after tweaks to the isolastic adjusters and newly added exhaust rose safety wire & spring setup), everything going great. Bike running strong, two first kick starts putting a smile on me face. Decided to take her out on highway and again all was great first twenty min or so. Then I began to notice an occasional drop or dip in power for a moment, like when you hit a small road bump. Happened a few times over next ten minutes. Got off the highway and when pulling over at a stop sign, engine just quit. Checked a few things, still had power to lights, still fuelled. Gave it a kick and all back on line again. Decided to continue on a side road and made it another few miles then another flame out. Pulled up and went through the electrical connections at coils, one terminal was slightly loose, but didn't seem like enough to break connection. Cycled ign key off/on a few times and wiggled all the HT connection after a no kick start. She fired up and off I go again. Another mile and another flame out. More checks of battery connections and EI cabling at timing chest, also worked the kill switch a few times, she starts and runs fine next few hours.

I'm going to go through all the wiring again. Any other suggestions on what to check? Coil failing?
 
Tornado said:
While out on yet another test ride (after tweaks to the isolastic adjusters and newly added exhaust rose safety wire & spring setup), everything going great. Bike running strong, two first kick starts putting a smile on me face. Decided to take her out on highway and again all was great first twenty min or so. Then I began to notice an occasional drop or dip in power for a moment, like when you hit a small road bump. Happened a few times over next ten minutes. Got off the highway and when pulling over at a stop sign, engine just quit. Checked a few things, still had power to lights, still fuelled. Gave it a kick and all back on line again. Decided to continue on a side road and made it another few miles then another flame out. Pulled up and went through the electrical connections at coils, one terminal was slightly loose, but didn't seem like enough to break connection. Cycled ign key off/on a few times and wiggled all the HT connection after a no kick start. She fired up and off I go again. Another mile and another flame out. More checks of battery connections and EI cabling at timing chest, also worked the kill switch a few times, she starts and runs fine next few hours.

I'm going to go through all the wiring again. Any other suggestions on what to check? Coil failing?
Click to expand...
I'm not expert in things electrical but think that coils don't experience off & on type of failures. Once they go, they're gone in my experience.
Cheers
 
Could easily be that the fuel cap isn't venting. Try another ride, when it begins to exhibit the signs you have described, open the cap. Be advised that this can be very dangerous, suggest that you use some safety wire and chase the convoluted vent first.
Are you using both taps?

Best.
 
Ign is Wassell EI which is an improved Boyer analog type. Has been pretty trouble free for three seasons now.

As for coils, ive had one suddenly die on my classic Mini and yes, it was permanently dead, but that's just one data point to go by.

Tank vent has been cleaned a year ago. Troubles only appeared sometime after a fuel top up (I'm running my small HiRider tank so like to top it up frequently) Think it took 4 Litres, just nearly half a tank. Was running single tap whole day. Usually when I shut off the tap when parking for a few weeks, engine goes through several sputters before it shuts off, not a sudden no warning quit like several times today.

Edit: one other observation I just recalled. At first fire up this morning I noticed the see through fuel filter on right side was showing a fuel discolouration, like weak tea. This tank was only a week old since last fill up. Always with non ethanol high test. Other side filter off reserve was looking clean and clear. Unknown what was up with that. But first quit happened much later in the day and both filters were clear then.
 
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It's not possible you're having blocked strainers inside the tank (top of taps)?
Work checking.
I would empty the tank into a large clean tub/container to inspect what comes out.
Cheers
 
Is the tank steel or fibre glass, discoloured fuel could be from a liner on a steel tank dissolving or the whole tank if fibre glass.
 
I got a length of fabric covered rubber fuel line off ebay. Stays supple and though all was fine until I started seeing tiny black
bits when I examined the fuel drained from the bowels. And this was on all four of my bikes. What I am saying is that all sorts of stuff seem to bung up things. If you take your tank off and do a complete dump you will be surprised how much particles you will see in your funnel screen.
However I will admit that it sounds more electrical than fuel.
 
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I had these symptoms a few months back about 200 miles after I'd de-rusted my fuel tank (distilled vinegar) and cleaned and serviced the carbs. There was the same tea coloured fuel in the bottom of the fuel lines. I flushed the tank again and cleaned the carb body and all has been fine for over 1000 miles since. Might be your issue, rather than ignition.

I put it down to not managing to get everything out of the tank when I first flushed it and the engine vibration liberated what I'd missed.
 
Tornado said:
More checks of battery connections and EI cabling at timing chest, also worked the kill switch a few times, she starts and runs fine next few hours.

I'm going to go through all the wiring again. Any other suggestions on what to check? Coil failing?
Click to expand...
Kill switch could be your problem, could be a lose connection inside the kill switch, get rid of the kill switch or by pass it and see what happens, lots of folks have had that problem and do you really use it, I got rid of mine over 40 years ago.
 
Tank is steel, not lined. Back when I got the bike three yrs ago I gave it a thorough cleaning with soap, water and aquarium gravel shaking to remove any built up etc, then Metal Rescue rust converter treatment. Been fine for three seasons used this way, some 3 or 4000 miles.
Carbs are new Premiers, less than 1k miles. Hoses are all modern ethanol rated fuel lines. New last season.
Will check tank vent and maybe drain float bowls to check for debris.
Still leaning to electrical gremlin as shut downs were sudden, no sputtering like seems to happen with fuel starving. And immediate restarting first kicks on two out of the three shut offs.
 
ashman said:
Kill switch could be your problem, could be a lose connection inside the kill switch, get rid of the kill switch or by pass it and see what happens, lots of folks have had that problem and do you really use it, I got rid of mine over 40 years ago.
Click to expand...
Yes that is a suspect here. I had it apart a few weeks ago to run some fine wet/dry tween contacts as a preventative after hearing Joe C's finding of kill switch issues. Might have made it loose some reliability. Alao potentially tweaked the EI cables running into timing chest as I was struggling a few days ago messing around with front iso adjuster. That wiring runs right next to that adjuster.
This EI should be better resistant to wire fractures as all connections embedded in epoxy on the stator plate. I have a Trispark to fit, plan was for the winter layover project.
 
90% of fuel problems can be electrical
90% of electrical issues can be fuel related

my 74 had an occasional cut out while riding, that allowed it to restart once I’d coasted to the side of the road. Once I got home and did a bit of research on here I had a closer look at the ignition switch and pulled it apart. Inside, the contact areas were crusted with green slimy muck. I gave it a thorough clean and rebuilt it and it then ran cleanly. However, the ignition key was a bit loose and the on/off/on clicks were quite sloppy, I managed to acquire a new switch off eBay and I’m now confident the very positive clicks won’t allow any sloppy switching.
 
Landspeedracer said:
90% of fuel problems can be electrical
90% of electrical issues can be fuel related

my 74 had an occasional cut out while riding, that allowed it to restart once I’d coasted to the side of the road. Once I got home and did a bit of research on here I had a closer look at the ignition switch and pulled it apart. Inside, the contact areas were crusted with green slimy muck. I gave it a thorough clean and rebuilt it and it then ran cleanly. However, the ignition key was a bit loose and the on/off/on clicks were quite sloppy, I managed to acquire a new switch off eBay and I’m now confident the very positive clicks won’t allow any sloppy switching.
Click to expand...
Yes another potential candidate. Switch is a newer EMGO repro of original Lucas that I put in shortly after getting bike, as original tested badly. Have since worked on the original and it might be worth swapping back into service.

Another point, I've been having weird voltage readings from my SparkBright warning LED for a long time (ever since swapping headlamp shells (fresh looking Hirider 5 3/4" to a vintage/weathered Roadster 7"). The LED is connected to the ign switched power and other wire direct to battery positive terminal. I rarely see the LED stay on one of its several colour/flash patterns which indicate different voltage readings. It has some heuristics to it to average out any rapid changes in readings...so a faulty contact glitching on/off frequently might give what I'm seeing. Or perhaps the LED unit is faulty. Was going to try a direct connect to battery/always on setup soon. I put in a new MOSFET R/R (Trispark) to give a better/smoother output than the noisy Typanium unit I had in there until a few weeks back. I've read that this is supposed to be much better for EI's, Typaniums are best for points setups.
 
I have had very short lived cut outs happen to me twice.

The first time was due to the ignition switch being faulty. Take a multimeter with you and next time it happens, check for 12v at the ignition unit, or even better, run a power line directly from the battery to your ignition unit, and put a toggle switch in the line, this will eliminate your ignition switch and kill switch. If after that it still cuts out, I'd start substituting the remaining wires in the ignition circuit.

The other time that I had similar symptoms to you, it turned out that one of the battery terminals was loose, but still connected, so that when I hit a bump, it would momentarily disconnect the battery and cut the power, and then reconnect. That one really surprised me.
 
Question for the clever ones at the front of the class…

When something like this happens (sudden intermittent power loss) does the power cause a spike when it comes back in?

And does / can this sudden loss / spike harm things?

What I‘m really wondering here is could this kind of fault be a reason why some folks see components fail whilst others enjoy long reliable service (like Tri Spark for example) ??
 
Tornado said:
I put in a new MOSFET R/R (Trispark) to give a better/smoother output…
Click to expand...
If that is a recent addition then worth checking that it isn’t causing an issue.
Coincidently I fitted one recently too and first ride out I had some random elec shut downs. I haven’t done any trouble shooting yet so it may be unrelated.
 
I had engine troubles a few weeks back - all was good and when I went to restart after a stop it would only run on one cylinder.
Nursed it home and during that time the dead cylinder would intermittently come back on line . After chasing down connections and fuel supply replacing coils fixed it so here is evidence that coils can have soft failure.
 
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