Topic: 350 igition question

[Green550F]

I'm considering making an upgrade to my cb350 ignition. I have a bad coil and may try to change over to CDI.

A few questions I have are:
Is there anything suitable out there?
Am I correct in thinking the plugs fire at 270/90 degrees from each other.
Do the plugs fire on opening or closing of the points?
How much dell is there in the points system?

I'm confident I can build an ignition circuit If I have enough info...

[heffay]

was looking for something else but got distracted by this

[rchrdms]

The plugs fire when the points close. When they open, current flows into the coils and builds up a charge. This charge gets pretty big, then the magnetic field  collapses upon the points closing and you have some 20,000 volts run to the spark plug.

My manual doesn't mention a dwell setting, just timing and points adjustment.

[tbpmusic]

I'm considering making an upgrade to my cb350 ignition. I have a bad coil and may try to change over to CDI.

A few questions I have are:
Is there anything suitable out there?
Am I correct in thinking the plugs fire at 270/90 degrees from each other.
Do the plugs fire on opening or closing of the points?
How much dell is there in the points system?

I'm confident I can build an ignition circuit If I have enough info...

It's a 180 degree twin, with all that implies.

Lot of headaches converting - why not get aftermarket coils from Mike's XS Shop.
About $60 for new coils/wires/caps, and it's virtually a bolt-up.

[kirkn]

The plugs fire when the points close. When they open, current flows into the coils and builds up a charge. This charge gets pretty big, then the magnetic field  collapses upon the points closing and you have some 20,000 volts run to the spark plug.

My manual doesn't mention a dwell setting, just timing and points adjustment.

Normal battery-and-coil, points-type ignitions spark the plug when the points OPEN.  When the points are closed, the current flows thru the primary winding in the coil thru the points to ground.  This current flow builds up a magnetic field in the coil.  When the points open, the current flow stops, the magnetic field in the coil collapses cutting thru the secondary windings as it does so, inducing a current flow which jumps the plug gap to ground.

[Green550F]

I was thinking they fired when opening...
Also how can it be 180 out of phase when the point's are at 90 derees from each other?

[Jay B]

I was thinking they fired when opening...
Also how can it be 180 out of phase when the point's are at 90 derees from each other?

The crank is 180 out of phase, IOW, one piston is down when one is up. Cam is driven 1/2 crank speed, therefore points fire 90* apart on the cam. And yep that results in an uneven firing order. They fire at 180* then 540*. (It takes two revolutions per combustion cycle on a 4 stroke) Old Triumphs used 360* cranks, pistons rose and fell together, and fired every 360*, giving an even firing order.

[rchrdms]

OK, I guess it fires when open. I should remember,  many times I've lined up the timing marks with the points just as they open.

BTW, the Clymer manual has a cool method for aligning the timing on your bike. You connect a test light lead to the terminal of the points for
the cylinder you are adjusting and connect a jumper clip to ground. The light shines when the points open, and you can adjust the timing by moving the breaker
plate advance or retard timing.

[tbpmusic]

Go here for the timing process on your bike -


http://www.hondatwins.net/forum/viewtopic.php?f=18&t=883

[Green550F]

What a relief! The failed left spark turned out to be a bad plug and not the coil!

This buys me time to make a CDI setup. I'm going to try and design a setup that'd be "universal" as a set of honda points... 

Once done, maybe I can recoup some of the cost by selling my stock ignition.

Otherwise, Here's the bike!