Shovel dies after 10 Miles? Help

[ACLX]

Hopefully someone can help me out, been battling this for a while.
76 Shovel, kick only, stock internals +.010 over, Super E carb, Dyna S ignition, teardrop air cleaner, drag pipes with baffles.
The bike has sat for about a year, if I put new plugs in it starts and runs good, idles well, it pulls decently, after riding for about 20 minutes it starts to feel like its not sparking, and then struggles to stay running without throttle and then it dies and I cannot get it started again. The plugs are sooty black fouled. Even after cleaning them I still can't get it to run again just after pulling them. I have thoroughly checked timing, advance, all ignition components, valves and pushrods, I know its something to do with the carb I just don't know what, I have tried reducing the jet size to the lowest I can find thinking its running too rich which it is, but I can't work out why.
Let me know if you have any thoughts, appreciate your time.

[rockman96]

Sounds more like something electrical heating up and breaking down. After its cool the cycle starts over(?)... Do you have a spare coil to throw on it for grins? I hate to say this after I've touted them so strongly, but maybe there's something going on with the Dyna S(?).

[JBinNC]

Sounds more like something electrical heating up and breaking down. After its cool the cycle starts over(?)... Do you have a spare coil to throw on it for grins? I hate to say this after I've touted them so strongly, but maybe there's something going on with the Dyna S(?).

I like the Dyna S as well, have them in both my bikes. But like anything electronic, they do fail. They will usually manifest an intermittent miss after the motor is warm, and sometimes do stop working completely. And then when they cool off, they will start working again. That can be frustrating to diagnose; replacement is the definitive test. (Can replace a Dyna S with points & condenser as a temporary test.) In my experience, the Dyna S has about a 12 year life span, but I have seen some that are over 20 years old.

Jim

[DustyDave]

I usually put a spark tester on one plug gaped close and ride until it acts up and see if ite spark is quitting or not. It's always good to know not guess.
When I was looking for a picture, Speedway had them for less than I paid for mine in the 80s. I changed to these when the city cop caught me riding a Moto Guzzi with my Oscilloscope in one hand, he was not amused.
Dusty

[farmall]

Thermal intermittents are common as others posted.

What DOES persuade the bike to start eventually? You left that out.

Ignition systems are consumables so I keep complete spares as there is no economic reason (you'll need an ignition eventually and they're not getting any cheaper) not to stock a spare.. The ignition might be fine but the coil might not. Ensure you get the correct coil, Dyna make good ones.

When swapping isolates the bad component the others can serve as spares. Replace the bad part in your "bench stock" and you'll be ready for the next time.

[confab]

Like everyone has said, it's most likely ignition related and you'll find you have no spark when this happens. (Which is really the way to diagnose it. Check it for spark when it won't start. Check for power to the ignition. If it's no/yes, then it's whatever type of ignition module you're running.)

For it to be the carb, you'd be looking for a sticking float, a collapsing filter in the tank or a vent that isn't venting..

[docmel]

Sounds like a possible fuel delivery issue to the carb, not the carb itself. Really take a close look IN your tank and any gas filter you might have. Arbitrary changing out jets is just going to cause you headaches.

Be more specific on how it dies. Does it sputter and die, or does it die suddenly like someone hit a kill switch?

Check you main ground and whatever ignition switch you are using

But the "new then the plugs get sooty" throws a wrench at my input

[Whoremonger]

Intake manifold leak.

[47str8leg]

Circuit breaker or ignition switch.
Disconnect your wire from the switch to the coil ( tape it up so it can’t contact anything) and run a jumper wire straight from the battery positive to the coil ( being that you no longer have a breaker use a male and female bullet connector for an emergency disconnect . Put the male end on the coil side and make it long enough to ground out the coil to the frame ).
This will eliminate your switch and breaker from the equation and only leave your coil and ignition effectively starting the trouble shoot from the middle of the potential problem.
If the bike continues to run fine then look at your switch or breaker.
If it continues to crap out check the coil or ignition.

If disconnecting the bullet doesn't turn off the bike then ground out the coil.
You cannot leave the jumper cable on after you stop or it will burn out your coil.
I put this jumper cable tucked away in the harnesses I make now for my bikes. That way if my switch or breaker fails on the road I can fix it in 5 minutes and at least have to deal with the problem later on wherever I intend to land.