Hello all:

My 1975 ironhead will run for 15-25 seconds and then stop,i have pin pointed it to spark,i put an other plug in the cable and no spark,then waiting a few seconds it will spark,or run again and stop.If cold it will run 15 to 25 seconds,if more warm 5 seconds. All help would be greatly appreciated.

Harbri

 

if you have points still in the ignition i would swap out the points and condenser

 

Check for loose connections at the ignition coil, and at the other end of the same wires.

 

Could be a short in the ignition circuit triggering the circuit breaker. When you change plugs it has reset then shorts again after a short time.

 

It has electronic ignition

 

Good suggestions above--loose wires or a short that's tripping a circuit breaker.

If you can't find any problems there, you may want to try another coil. The symptoms you describe sound like a failing coil, except when mine failed, it took longer than 15 seconds to heat the coil up enough to make it fail. Mine would work OK for 10 to 15 minutes of riding, then my bike would die when the engine slowed to an idle. And it took quite a while for it to cool off enough to start working again, at least an hour or so. It's not a bad idea to have a spare coil on hand anyway. When they fail, the best and quickest way to determine that is to try a new one. Just make sure you get the correct kind of coil. Coils for points and coils for electronic ignition are different.

I hate to say it, but it might be your electronic ignition that's failing. Electronic components can be very sensitive to temperature, working OK when cold and failing when warm, or vice versa, working when warm but failing when cold. To test it, you can buy a can of the compressed air used to clean out computer keyboards. Turn the can upside down, and spray the heck out of your electronic ignition module with the cold air that will come out. I'd start spraying immediately after starting the bike and see if it will keep running longer than 15 seconds as you spray it with the cold spray. (I tried this same trick when I suspected my coil was failing, but I couldn't get the coil cold enough inside to make any difference.)


Good luck.

 

+1

In my limited experience the symptoms have been quite similar. And there is no reliable test for either component other than replacing with a known good one.

Definitely handy for an IronHead owner to have spare parts available - especially prone-to-failure electrical parts such as generator, regulator, coil, and solenoid.

 

Where do the wires go to the other end ,i cant seem to follow them.

 

I changed the coil this afternoon and no difference,runs 10 seconds.I all so dont hear a circut breaker klick back to life which i have heard before. Any way which breaker would it be,i have 3 under the seat and one on the + batt cable.

 

if you dont know what type of electronic ignition you have you need to post pictures / one of the cam cover center cover off ? what is in side and one if it has a module what it looks like