Hitchcocks Forum

Hi everyone. I have fitted Thor spark electronic ignition to my k2f magneto,and the Connie is running well. My only issue is when I go to restart the bike sometimes ie switch ignition on , I get a surge and smoke from the back of the carb . Sometimes a bit of a pop. I know that when I switch on,both plugs spark and it's probably igniting fuel vapour left in the combustion chamber. Has anyone had this trouble? And are other electronic ignitions the same. Many thanks calvin

Yes, it's quite common. The system uses a 'wasted' spark so both plugs fire at the same time. This means that while one cylinder is on the firing stroke the other is on the inlet and as you say, there is sometimes enough fuel present to ignite and cough back. Even some bikes fitted with electronic ignition can sometimes do it, my 1980s BMW does now and again.

REgards, Mark

Thanks Mark! If it's common I will learn to live with it. Have no problems at all when running . starting well ,idling good and grunts like a gooden. As long as no flames I'll be happy

That is the only risk, a spit-back that ignites fuel. If you don't have a filter on you could try a bell-mouth with a gauze on it, these were used as flame traps back in the day.

REgards, Mark

it was interesting to read of the "blowback" using the thorspark unit, i have just fitted one and i have the same weird symptoms!! a firing when switching on and black smoke coming out of the carb!! i know mark suggested a gauze filter , but has anyone else come up with a answer since this subject was first raised?? polly