So pulled it down tonight, thought it might be a fuel issue/blockage, despite the fact it didn't start to splutter and die like it was starving of fuel, it just snuffed out (idle is a bit low it's got a wandering idle/hanging up RPM after pulling up at lights which I was just about to start searching for. Anywho, fuel in the float bowls, float bowls look clean enough, plenty in the tank, so save for a blocked fuel filter (unlikely) I guessed the fuel side was ok.
One of the plugs looked a bit black, one looked ok. Did a spark test, left side cylinder sparked fine. Right side, nothing. Swapped plugs, checked other earthing bolts for the spark test. Nothing at all. Noticed the right side ignition coil was getting quite warm to touch, yet the left was still cold (bike hadn't been run for a couple of days so there was no reason for the coils to be so hot after a short cranking duration).
Both coils were showing 0.06v with ignition off on a voltmeter. Ignition on, and left side coil (the sparking side) showed 11.8v. Right side coil, 1.15v. I thought I'd misread the decimal point location, but no. I didn't really have a point to measure the voltage going in to them, but the one wire comes of the CDI plug and splits into two to go to both coils so I'm not too fussed. Plus the good coil is nearly outputting 12v so it's going to be getting that input.
They were a 2nd hand pair of unknown parentage to replace the originals with frayed plug leads so I'm guessing one is dead. I'm a bit surprised (and anyone feel free to weigh in on this one) that it didn't simply run like a bag of *@%^$*@%^$*@%^$*@%^$ on the one cylinder (or at least want to run or start). It was backfiring super loud through the exhaust when the throttle was held wide open and I was trying to start it, but with throttle mostly or fully closed no backfiring; a couple of backfires through the carbs from time to time. I would have thought it would have been obvious running on one out of two cylinders. Am I way off?? Perhaps there's two separate problems with the bike??
I'll probably go for some aftermarket ignition coils, they're cheaper and as long as they fit fine I'll be happy.
Cheers
Phil
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