No spark no matter what

[solarae]

Hi folks. I'm a new member hoping to get my bike going. I bought this bike not running. It needed a new spark plug cap supposedly. Anyhow, I have replaced the CDI, magneto, and spark plug. All seem to check out with a meter. No kill switch. All wiring correct with good contact. Motor turns good. Still no spark.
Any suggestions.
Thanks bunches, Edy

 

[BoDean_LP]

Sounds like you may have some sort of grounding problem. I don't know. I've been having similar troubles.

 

[2door]

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

 

[Kioshk]

By "magneto", do you mean coil? The magnet itself may be pooped, or timing may be off if the magnet's woodruff key is bent. I'm assuming a China Girl, and that you've already confirmed no-spark visually (with the plug out).

 

[solarae]

Its a generic HT, chinagirl
I haven't gotten as far as identifying the carb.
I'm grounding the plug to the engine fins. Not even a hint of spark, not once.
Yes, I mean the coil. Its a new one.
I may be new to this list and 2 strokes but I'm not new to motors and spark plugs.
What should I be looking for regarding lack of ground and more on the timing would be great too.
Thanks for everything so far.
Edy

 

[2door]

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

 

[solarae]

Sorry, I didn't think anyone was talking down to me but I did want to get it out of the way that when I say "no spark", I mean NO spark, not no gas etc.

From what I've already researched and seen, the CDI wire is glued in and not readily replaceable. The wire is copper. I may try a better boot today but I believe I have good contact with this one. I've jabbed one meter probe through the wire, close to the potted box and touched the other probe to the spark plug holder and I get continuity.

As far as timing, if one runs a magnet past a coil to produce current, that current doesn't have to occur at the same time a valve opens to just produce spark, does it or is there something I'm not seeing here.

The magnet seems strong in that the coil is fairly hard to unstick from it when the mounting screws to the coil are removed, allowing it to move and stick to the magnet.

I'm trying to be overly thorough in my descriptions in the hopes that it will help others.

Thanks again, Edy

 

[Greg58]

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.

 

[2door]

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.

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

 

[Greg58]

Tom I too had the end crimped on top of the insulation, mine was on one of the kill switch wires tho. I wonder how many others have replaced parts because they didn't find this.

 

[fatdaddy]

Take the coil back out and everywhere it touches metal, sand off the varnish. Clean off any grease or corrosion on the magneto case also. This should get the thing grounded properly. Sand the varnish off where the screw and the black wire goes on the magneto and make sure thats a good ground.
As long as you have the coil out, Take the nut and washer off the magneto so you can see where the magneto key is. Then, piston TDC and key at 2oclock. If not at 2, then flip the magneto around.
Some of the plug wires are glued in, some are not. Dig out the glued in one and replace it with a good auto wire and boot. It will look like the end of a wood screw that you screw the new wire into.
Then blue to blue, black to black. Never use the white wire for anything. Do not hook up the kill switch yet.
I think thats everything bro, Let me know what happens.
http://motorbicycling.com/showthread.php?t=26591&highlight=magneto+timing ... Pic# 1 in post#9 is what it should look like.
fatdaddy.
***************************
IT'S YOUR BIKE, BUILD IT YOUR WAY.

 

[solarae]

The black wire has continuity from the engine casting to the CDI.
The blue wire has continuity from the coil to the CDI.
It's getting cold and dark out so checking the position of the magneto key might have to wait. Maybe I'll get it into the garage tonight but it also tends to leak gas so it has been banned by the SO who also likes to tinker.
I still don't understand why the timing has to be right in order to create spark but of course it would need to be correct for that spark to ignite the fuel.

Thank you all for your time and consideration, Edy

 

[fatdaddy]

The black wire has continuity from the engine casting to the CDI.
The blue wire has continuity from the coil to the CDI.
It's getting cold and dark out so checking the position of the magneto key might have to wait. Maybe I'll get it into the garage tonight but it also tends to leak gas so it has been banned by the SO who also likes to tinker.
I still don't understand why the timing has to be right in order to create spark but of course it would need to be correct for that spark to ignite the fuel.

Thank you all for your time and consideration, Edy

Don't know why, Can't explain it, I'm no electrical engineer. But mag in backwards, no spark.
fatdaddy.
***********************
IT'S YOUR BIKE, BUILD IT YOUR WAY.

 

[Greg58]

FD you forgot to mention that the cut outs on the magnet should be at 6 and 12 oclock

 

[solarae]

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.
Tom

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

 

[2door]

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

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

 

[fatdaddy]

I've been wrong before, And I guess I might be now. I thought I remembered if the mag was in backwards, no spark.
It sounds like you did everything right and should be getting a spark. So 2door is probably right. It's GOTTA BE defective parts.
fatdaddy.

 

[solarae]

So I got the nut off, and the key looks like its in the right place. I even pulled the magnet just to look at it. If it was backwards (inside out) the key would be like at 10 o'clock rather than 2 o'clock when the piston is at TDC, right?

 

[fatdaddy]

So I got the nut off, and the key looks like its in the right place. I even pulled the magnet just to look at it. If it was backwards (inside out) the key would be like at 10 o'clock rather than 2 o'clock when the piston is at TDC, right?

NO, The mag itself would be in a different position. The crank and keyway can't move. it will always be 2oclock at TDC.
fatdaddy.

 

[solarae]

Thanks for the ohm values. I've seen those ones before. I get very similar readings on all 3 CDIs.
I'll go from original to newest.
1) zip on all 3
2) 119,114,155
3) 132,127,155
4) 7.02,6.72,6.79
I'm thinking this last value is wrong on the chart and that the CDIs are good.

Coils
Original
1) 3.1
2) zip

New
1) 3.2
2) zip


So maybe I got a bad coil. It was kind of rusty on the outside when I opened the package but I don't know if that is really significant.

Anyone want to measure a known good coil?

Just because everyone copies that same chart, doesn't mean its correct but I think we are getting somewhere.

Thanks again, Edy