At idle I disconnected the VOES at the carb and there was absolutely no change in RPM, so potentially there is a VOES problem.

I'm also noticing that the exhaust coming out of the rear cylinder is much faster than that coming out of the front cylinder. Both are at constant speeds rather than being all over the place, but could this indicate a timing problem? Just seems weird that a timing problem would lead to an intermittent issue that happens randomly during rides, rather than being a constant problem, ya know?

 

Also note that for the sake of the test I did plug the VOES port at the carb (per the manual) to make sure it was fully and effectively no longer sucking air.

 

Hi again,

Since_1968, I feel like an idiot for not giving your original advice much thought at the beginning but after testing a bunch of things I ended up swapping out the right side gas cap for a vented one and that seemed to really do the trick!

Once I made that swap I went for several more hour long rides with no loss of power! I hesitated to post anything since I didn’t want to jinx it, but I took the bike to work today and had the motor cut out on me… no sputtering or build-up to dying like usual, just a clear cut out when I was shifting to 5th. Pulled over and started up after 30 seconds, but frustrating and weird nonetheless.

I just put sea foam in the tank since there’s always been a bit of carbon buildup on the front spark plug, but that’s the only variable…

Pretty weird, it’s at least more consistently safe than ever but I guess Im not out of the woods just yet.

 

Well, I was going to say I love a Happy Ending, but it sounds like you're not out of the woods yet. Crap! I would separate thinking about the front spark plug as something else to deal with. The main problem is the motor cut out, just like before. I would still suggest installing a new fuel line, mostly since it's a reallly cheap thing to try. The line could be partially collapsing and it was a parallel problem to the fuel cap vent. Also, look into 98 Fatboy's text about a vacuum operated fuel petcock. Your '92 wouldn't have had it originally, but maybe somewhere along the way one got installed.
The carboned up front plug (I assume the rear plug is clean) is more likely something on the ignition side. Single carbs seldom cause a problem on just one cylinder, that would be really odd. I would try a fresh set of plugs and plug wires, plus a diagnostic check on the coil. I can't remember the specs, but somebody here will if you don't have the info as to what you should see with a multi meter. One side of the coil might be weak, leading to a weak spark and incomplete combustion. Keep at it, you'll get there.

 

If the idle rpms don't drop with the voes disconnected, could be a bad switch, broken ground or other connection. If the connections and switch are good and the rpms still don't drop at idle, you have a horrible intake leak not allowing enough low rpm vacuum to activate the switch. That might also explain the black front, clean rear plug and uneven exhaust. Intake leak can make them run extremely hot on one or both cylinders.

Just because a coil ohms out good, does not guarantee it'll fire under load and/or when it's hot. The way it's cutting out sounds exactly like a coil that wants to give up but, those ignition switches are bad to get corroded, lose connection so don't totally rule that out either.

If it were mine, I'd check the voes (ohm meter and hand vacuum pump), replace the 3 intake seals and check/clean the ignition switch. Replace the coil if it still acts up.

 

Thanks fellas, this is still an on-going development so I'll keep the forum updated when I have more info. I re-tuned the carb myself and all was well for a time, but just had the motor cut out and die on me again today, so once again I'm not out of the woods. The re-tuning did take care of the carbon-fouling on the plugs though. My concern had been that maybe they were getting so fouled while riding that the spark became super weak and wouldn't ignite turn the motor over, but it looks like that's not the problem.

What I can add is that it's definitely not a vacuum-operated petcock since I put this one in myself.

Next step is to follow t150vej's order of operations. Stay tuned, hopefully I can get to this soon.

 

A few things to keep in mind besides post 15 - the cam sensor could be going out again (not likely).

If the main ignition module goes bad - they die and that's pretty much it. They don't act up intermittently. But, a power interrupt or low voltage will cause them to cut out and require a restart.

The voes won't cause one to shut off unless it or the hose is leaking vacuum really bad. If it or the electrical connection is bad, it'll run at low timing up to about 1800 rpms but otherwise has no effect.

 

I may have fixed this actually, but with an unforeseen solution. I removed the split tanks for some other maintenance and when I did I noticed a pretty sizeable sloughed-off piece of tank liner float into view in the left-side tank. So of course I removed that, went on a test ride, and after 60 miles it's still been running great with no sputtering or dying (usually it would cut out on me at about 20-30 miles, sometimes less...). So my guess is that tank liner was wrapping itself around the fuel filter at the petcock at random times and choking the fuel flow.

Fingers crossed! I'll let ya know if I'm getting ahead of myself, but right now I'm remaining hopeful.

 

Actually that's pretty common.. My 98 is starting to give me problems as well..

 

Sounds like you've got the source of your problem. It's likely that if you've got one big flake floating around in there you could have more, or you will have. You could buy one of those relatively cheap borescope extensions for a cell phone and get a good look inside the tanks. You may need to tumble your tanks with some nuts and bolts inside to get all the old coating off. There was a thread on here where a guy taped up a blanket around a tank and then tumbled it in his clothes dryer with good results and not a lot of labor. Then you could google tank coatings and how to apply them. I've never done it but might have to in future for an older Norton I'm working on at a snail's pace.
My grandson now owns my '91 Springer. Knock on wood but no problems with the factory tank lining at 115k miles.