one spark or two?

[lingeringstin...]

Been looking at the Honda CMX250 twin clone engine I picked up and it seems to have an electronic ignition with only one point of pop. It' s supposed to run two separate coils but I don't see the point. Both pistons go up and down at the same time and I can only see one sender lug thingy on the alternator, so surely that means it runs a wasted spark system where the pistons pop alternately and there's a wasted spark on the exhaust stroke? If that's the case then surely I could just keep my existing single coil ignition setup and just run two spark plug leads off of my one coil. It would greatly simplify things if I could do this instead of having to rewire things for two separate coils.

[rcbikeracer]

running two spark plugs off one coil may result in the spark taking the path of least resistance, ie the spark plug that is not under compression.

[Teflon-Mike]

The 360-crank Benlys do run a single trigger, single CDi or points 'lost-spark' system, with a single Siamese coil, with twin HT-Leads.

Do you have one or two CDi's?

Where I have slapped 360 motors into Super-Dreams, I have retained the twin CDi's and twin coils, and taken a single trigger signal to both from a Y connector, manly for simplicity/revertability/reliability.

Firing two plugs off a single, single winding coil, splicing the HT lead, is a bit iffy to my mind; you are a likely to get just one spark at one plug, as volts take path of least resistance, or two much weakened sparks, or no sparks, or any combination of!

Using a siamesed coil, and notion of nicking one off a four to try it, seemed reasonable; but issue of coil impedance and load on the CDi deterred me, though that's how Honda did it on the Benley's... and they seem to use the same CDi.. so a CM/CD125/200 possibly a CB Two-Ffty 'twin' coil, would probably do the job.

Not sure how much you would save over two coils, though bar having to splice a second spade to the LT feed wire off the CDi, compared to using two separate coils..
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[lingeringstin...]

On my single popper I'm currently running an old Lucas oil filled coil from some car. It's a setup I've always used because it seems to throw a great spark no matter what spark plugs I've ever used, so I just assumed it would do two spark plug leads at once but I can see where that might not work. It would probably just always spark at the plug with the least resistance. I might test this theory out anyway just to see what happens on the workbench but not on the bike. I just really wanted to see two leads coming off the one big coil just for the wierdness of it.

From a cost standpoint the number of coils isn't really an issue here. Newfangled generic coils seem cheap and readily available and somewhere I saw reference to the fact that on at least some of the Honda twin motors the two coils were just jumpered together by a short wire anyway. So for wiring purposes it's pretty easy to just wire it all up as a single and then just wire the two coils together at the end of it all.

Or maybe I could wire up my spare enormous Lucas oil filled coil that I've never used for the past 20 years. That would probably work. Those coils are bulletproof.

Apparently this engine is supposed to use a single CDI triggered off the alternator AC and supposedly you can push start the bike with a dead battery.

[Teflon-Mike]

[lingeringstin...]

I think the coil I'm using at the moment is something like a Lucas DLB105 or 198 or something like that. I took it off some car that was abandoned on the side street near the flat I was living in at the time. Pretty sure it was electronic ignition and was something like An Astra but it's been so long ago I can't remember. It's been a brilliant coil on my points ignition.

[Triton Thrasher]