Have a 99 EVO Heritage with s&s. 96. Rear cylinder will stop firing after 20 min run. Them let cool and will come back. Have a single fire ignition with new coil. Any ideas would help. All new plugs an wire. Ignition is in nose cone and came from Mid-USA

 

Did the old coil do the same thing? Sure sounds like a coil. Swap wires on the plugs and see if the miss moves from one cylinder to another.

 

Old coil did the same thing. Wires from ignition module are all new. And compression is 122&120 with bleed down looking great.

 

Did you try swapping the plug wires as suggested above? If it changes cylinders then there is an ignition problem. If not then pull the plugs and check the condition as it might be an air/fuel delivery problem instead.

 

Whose ignition are you running in the nosecone?

Several models, including Crane failed a lot in the high heat region inside the nosecone.

I'm going to say you need to reinsert the original designed system with the optic sensor timing trigger, and use a frame mounted aftermarket ignition module.

There should be a location for a standard ignition module, often they are located in the steering neck region, and some under the seat.

The only other possibility is that when heated up either some of the main ignition wiring is shorting to the frame, or you have a conductor broken inside of it's insulator. When this heats up the insulation stretches and the wire stops making contact.

 

I was obviously drinking..... You can't do that with single fire.

You can swap both ends of the wires to isolate a wire or swap the plugs to isolate a plug, and swap primary wires and one end of the secondary to isolate a single fire coil.

 

I have new plug wires and have tries two sets and have a same problem. I think it might be heat on the module as suggested and have a new module I will try in nose cone.

 

Can't think of anything mechanical that would act like this. But checking all possibilities

 

I just installed a new ultra ignition module in the nose cone and bike is back to life. I have a very easy start and both cylinders are firing. Just need to do a 30 to 60 min run now to see if all is fixed.

 

It's really a pain the issues you get with a bad ignition module. Glad you were able to get it fixed.

Not all manufacturers units went bad in the nosecone. Whose ignition did you have? Whose did you put back in?

I wound up replacing the entire ignition system before I replaced the module and it fixed mine. Now I know my system isn't all 26 year old parts ... lol