Ignition

New guy looking for a solution to why left cylinder will not fire?

Saber13 said:

New guy looking for a solution to why left cylinder will not fire?

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Left Spark plug? Left Plug wire? Left Coil? Left Points? Wiring to left coil? Etc?

Do you have a Boyer ignition?

Saber,

All wasted-spark EIs, which include Boyers and practically all twin EI systems, have a common output to both coils. It is not possible for these systems to affect an ignition problem on one side and not the other. As pvisseriii pointed out, focus on those parts that are unique to a side, like coils and their input leads, plug wires, and plugs.

rick in seattle said:

Sabe

All wasted-spark EIs, which include Boyers and practically all twin EI systems, have a common output to both coils. It is not possible for these systems to affect an ignition problem on one side and not the other. As pvisseriii pointed out, focus on those parts that are unique to a side, like coils and their input leads, plug wires, and plugs.

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Quite the contrary. Try disconnecting one of the pickup leads on a Boyer and see what happens. There have been many cases of an intermittent open of these leads creating a misfire on one cylinder with the Boyer posted here.

I've encountered problems with spark plugs recently with both, Boyer and Points systems, just because you have replaced them doesn't mean they work. Swap them over and see if the problem changes.

Jim,

The Boyer module schematic (lifted from Dave Comeau's site) appears below:



It would be good for all of us to agree on the point as to whether a wasted-spark EI can affect only one side of the ignition. I've read the past postings that complained about intermittent connections of the yellow and white sensor wires to the boyer module. And certainly some have posted failures associated with a single side. I don't run Boyers myself, but I do know how to read a schematic. While a corrupted input can for sure cause misfirings, these misfirings must occur simultaneously on both cylinders, since the Boyer OUTPUT is common, between the collector of Q6 and ground, and drives the coils in series as a single load.

This point may seem trivial, but it provides a valuable tool for diagnosing misfires. It would provide a great service to me and others on this forum if someone could explain, considering the schematic above, how any wasted-spark EI can cause a failure to one side and not the other.

I do not think Saber13 said anything about a Boyer or any other type of ignition for the matter.
What say you, saber13?

Rick, I too, know how to read an electrical schematic. I'm stating my personal experience. I had a misfire on one cylinder with my Boyer ignition. Knowing it couldn't be the Boyer, since both cylinders would have to misfire, I troubleshot the hell out of the carb on the affected cylinder. All to no avail. Eventually, I got around to removing the points cover. Don't recall the exact sequence of events, this was some ten years ago, but I eventually stumbled upon a broken wire from the pickup coils. I couldn't see the break, for it had fractured inside the insulation. Being an ex-electronic tech, I was using a multimeter. Noticed when I wiggled the wire it went from zero ohms to infinity. Anyway, I replaced the wire and the bike ran fine. There have been a number of others running Boyers afflicted with the exact same problem using the exact same fix. This being the case, I would conclude I don't totally understand how the Boyer works. Your schematic does not show the pickup coils that trigger the module. Maybe looking at a schematic of the pickup coils would shed some light on the subject.

I would suggest that since a Boyer and most electronic ignitions fire both coils at once, that a missfire on one side only is a general missfire that manifests itself on the weaker cylinder..the one with slightly less compression, or inaccurate mixture or whatever.

Getting back to the original question, there's nothing in the question that even points ( no pun intended) to ignition. It could be anything from a faulty coil to a missing piston for all we know.

More information please.

I would argue, that although both plugs fire each time, only one is firing at the "right" time - i.e. during compression. The other is firing during exhaust. So let's say the left pick up wire is broken - the cylinders will both fire when the right cylinder is in compression, but the left will be firing duing it's exhaust stroke and won't do you much good in the go fast department. Therefore you could get a situation where it "seems" only one side is firing.

Anyone buy that?

napanorton said:

I would argue, that although both plugs fire each time, only one is firing at the "right" time - i.e. during compression. The other is firing during exhaust. So let's say the left pick up wire is broken - the cylinders will both fire when the right cylinder is in compression, but the left will be firing duing it's exhaust stroke and won't do you much good in the go fast department. Therefore you could get a situation where it "seems" only one side is firing.

Anyone buy that?

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Not me, it doesn't work like that. The signal coming from the pickup is a pulse and it occurs at each revolution since there are two magnets on the rotor and two pickups. Boyer makes a crank mounted ignition (Steve Maney sells it for one), it has one magnet and one pickup. I think Boyer uses two magnets and two coils on their cam mounted ignitions to get a better signal since the cam is turning at half the speed of the engine.

As to why fixing a wire on the pickup would cure a misfire only on one side, I will file that under the things that go bump in the night many of which seem to be associated with Nortons.

Jean

Ooops, forgot about the two magnets. Thanks for correcting.

Wow you goys are a wealth of quick info. Trouble shooting and controlled substition to date, plugs, plug wires and points. All stock ignition system, totoal stock 75. Will swap coils next week when I get back from Oklahoma.
This was a Christmas/Retirement present, along with a controlled budget. Thinking of Tri Spark as first upgrade.

Talk to fred at old britts about the system he sells, im very happy with it.

Will do, electric starter is nice, but I feel the need to kick start and not worry about breaking a leg. As long as I can kick, I can keep on riding.
Thanks

Hahaha! Took me a bit to figure the kick back out. Ankle hurts just thinking about it. No problems since then. Purrs like a kitten.