cdi ignition using point type coils

[lwb140]

anybody ever tried to use point type coils with a cdi ignition ?? im sure there is a reason the 800 upgrade kits came with new coils too but thinking about trying it any thoughts ?? anyone know if the 800 kits came with a new firewall ?? wade

[harleysportster]

They would probably burn out quickly. did you ohm out your coils. They should be 200 to 300 ohms.
To test the coil, measure the ohms between the primary stud terminal and the high voltage spark lead and between the high voltage spark lead and the small grounding wire. I believe 200-300 ohms is an acceptable range. Also test between
the lead to the ground connection to the primary terminal of the coil...it would be from .1 to . 5 ohms.

[lwb140]

think im going to try it , ill check their resistance and see what they are compared to other cdi ones i like the mounting of them for my jdx4 440/22 project wade

[400brian]

A 340/S engine I purchased a few years back, and one that I suspect was used as a test engine, had the points type coils mounted on the end of the fan tower ( typical 00/JDX location ). I assume it worked.

I just received two pairs of replacement coils for the 340/S - Cyclone / Liquifire application. One set from Pat's Small Engine, the other from Manufacturers Supply. I suspect that DK will have them now as well. I doubt anyone lays in too large an inventory of them. These are of course aftermarket, SPI and Parts Unlimited boxes, who knows who actually made them or where.

[JDT]

My grandfather used to say "Motor oil is motor oil".
What he ment was it doesn't mater what brand you use as long as it is clean and there is enough in there.

A similar idea is a coil is a coil.
As long as it fits it will probably work. Electrically external coils are the same. I would add to what Harley said that some measure as low as 150 ohms.
Whether there are two or three wires or connections is moot. Some use a seperate ground wire, others just and in and an out connection.
But either way the ground has to be clean and electrically good.
Disimilar metals corrode, oxidize or whatever. Mounting coils to aluminum makes it even more important to maintain a good ground.

One key point is the high voltage wire that runs from the coil to the spark plug. Some coils have a perminate connection that is epoxied or encapsilated to the coil body.
On this type of coil if the high tension wire is bad than you have to replace the coil.
Others have a replaceable wire. But that advantage also has a disadvantage.
On our CCW's for example the wire screws onto a threaded stud that resembles a sheet metal screw.
Problem is once again a corrosion issue can take place here.
If you suspect a problem with weak or no spark or as part of the rebuild process, unscrew the wire from the coil and examine it closely.

If you find the threaded screw all rusty looking, corroded or broken off than you found your problem.
Many of the brands used a rubber boot around the high side stud to keep moisture out. After 30 years the boot deteriorated or fell off and alowing a path for moisture to attack the connection.

Same goes for the connection at the sparkplug boot. Check these very closely with both a meter and your eyes.
Any corrosion of the wire itself or the plug cap will create a spark problem.

If you are dealing with an engine where the coils are not mounted to the engine itself the ground connection is critical.
If you have an engine that uses simulationeous firing plugs than these coils are differnet.

There is such a thing as high output coils. An example of this is the RED racing coils Cat used on the early EXT's.
Again a tradeoff. Sure the spark was huge but as the coils had only 90 ohms resistance they went through points in a hurry.

Also if you have failing spark at high RPM's check your condensors carefully for one that is breaking down.
And a weak spring on the points can cause issues at high RPM's.

Also pay attention the the insulating washers on the point arms. A missing or broken washer will kill spark on one cylinder.

Don't forget the retard cam on the flywheel. Missing spring or sticky action will make you go mad trying to figure out the problem.

And the plastic lobe that rides on the cam. And the ground connection under the points and on the internal coils. And the five pin connetor on the engine.
Any bad connection will sooner or later rear its ugly head.

[HEWTECH]

Don't do it...the points coil has much thinner windings (and more resistance) & cannot handle the additional current from the CDI. When it fails, there is a chance it could short out the CDI & on the stock CDI, this could cause a failure.

You need to stick with the stock coils. They were not that bad for reliability or cost, so using them is no disadvantage.....Scott