03 Speedmaster Ramdom Firing Problem

Good morning and welcome in.

I recently had this problem with my 06 Scrambler. It turned out to be a loose plug wire connection on one ignition coil.

I was about to begin to look elsewhere, until I backed up and started at the beginning. I even got a new pair of plugs out of the whole adventure. Good luck and don't forget to "kiss"!

 

These things are invariably solved by eliminating what it can’t be.....

Going back to first principles you describe a bike which has had its wiring and fuses comprehensively checked. It turns over but does not start or cuts out while running? The starter circuit would therefore seem to be ok. You press the button and it turns over consistently? That would rule out clutch switch, sidestand and gearbox lockout switches plus the starter relay and dodgy fuses or a poor earth (but slacken, wiggle and re-tighten because it never hurts. The strap bolts to a stud on the underside of the engine just in front of the swing arm.)
.......which brings you to an intermittent problem in the ignition circuit. I simply mean the coils being energised by 12v from the battery and having their power cut to induce a spark. A misfire would suggest a coil but both coils dead? Unlikely. You have replaced the most likely culprit, the pick up coil. It is not unknown for a duff one to be sold as new stock but unlikely. The igniter itself can only be thoroughly tested by substitution but a nil output voltage test to the coils is conclusive of igniter failure although a positive result could disguise a problem on the voltage switching side.

Anyone local to you with a carbed Speedy? If yours is playing dead switching igniters will provide immediate proof if yours then fires up. It is a 10 min job......nor will it hurt the ‘volunteer’ igniter.

You can then buy a replacement with confidence.....