No spark no matter what

Wlcome to the forum.
To help you we need a little information. What engine, what carburetor and please tell us how you're checking for ignition.

Tom

I'm not talking down to you be we have no way of knowing your experience and knowledge. There have been questions asked about "spark" and an engine that won't run only to discover that the man had the carburetor mounted upside down.

Have you by any chance removed the magneto rotor (magnet) from the crankshaft? It can be installed backwards and if so the ignition timing will be off.

The kit supplied spark plug boots are notorious for bad electrical connections. You'd be better off with a good automotive quality plug boot. I'm assuming you replaced the plug wire when you replaced the CDI? Did you use resistance wire or one with a metal conductor? Resistance wire can give you a problem if it isn't installed in the CDI correctly. The non-metallic core must be in contact with the threaded connector in the base of the CDI's terminal plug.

I'm also assuming you have wired it correctly: Blue to blue, black to black and the white wire isolated from touching any metal parts of the engine or bike frame.

Tom

Greg58 said:

I had one engine that had a bad ground, the black wire on the coil was not making good contact. I took the coil off sanded the back side to get to bare metal and replaced the wire up to the cdi.

Click to expand...

Correct, and there was a member recently who got two bad CDIs back to back.

As far as timing, no there's no valve timing but there is ignition timing which is supplied by the solid state circuit in the CDI. If the magnet is on backwards the electrical 'trigger' happens out of sync with the piston's position.

Greg's suggestion is valid, as always. Check continuity through the wires, blue and black from the end of the wire to where they exit the magneto coil.

Another thought is what kind of connections are you using to splice the blue and black wires? The kit supplied butt connectors have been known to cause trouble. Personally I had one where the blue wire connector was crimped around the insulation and not touching the conductor. We always recommend those splices be soldered and protected with heat shrink tubing.

Tom

solarae said:

Can anyone elaborate on this.
I'm working on getting the magnet off , reversing it and reinstalling it. Might have to run to town for a faucet puller.

Thanks, Edy

Click to expand...

Okay.

The lobes (magnets) on the rotor are indexed by way of a key and keyway. It is set up so the magnet passes through the coil at a certain time during crankshaft rotation. If the magnet is installed backwards, and it can be, the magnets pass the coil at the wrong time thereby producing a spark at the wrong time/piston position. Key word here are 'produces a spark'. Even if the rotor is installed wrong there will still be ignition so your plug will fire.
This fact sort of steers me away from the rotor(magnet) being wrong because you've said the plug never fires.

As I said earlier there have been cases of a man getting multiple defective parts. Not common but it certainly would make for a head scratcher.

I'll have to look for it (lost my copy on an old computer that died), but there is an ohm reading post that I put up a couple of years back that gives exact resistance readings that you should see when checking the CDI and magneto coil. Maybe someone has that handy and will post it here for you. It's not just a matter of continuity as you said you'd checked for. There are specific numbers that your components must match. An accurate ohm meter, either analog or digital is needed.

Tom

EDIT: Found it: Here is what you need to see>
Use Low Ohm-Meter Scale About 200 Ohms

Magneto Coil

1) Check Ohms between BLACK wire and WHITE wire. Reading should be around 2 Ohms
2) Check ohms between BLUE wire and WHITE wire. Should be around 300-400 ohms.

CDI

Use Ohm Meter High Scale About 200-K
1) Positive lead on BLUE wire and Negative lead on BLACK wire should read infinite (no activity)
2) Positive lead on BLACK wire and Negative lead on BLUE wire. Should be about 130-150 K-ohms
3) Positive lead on Spark Plug wire and negative lead on BLUE wire. Should read between 135-155 K-ohms

Switch to Low Scale 20K
4) Measure between Spark Plug wire and Black lead. Should be about 2.5 - 2.7 K- ohms