CDI is Toast. Payday is FRIDAY. Anyone have any dirty hacks?

[HeadSmess]

Something else must of happened. There is no way that a wire hooked from the CDI directly to the plug would cause the CDI to burn up. It has to be something else like a CDI ready to go. Every engine that the spark plug wire is made with actual wire in it connects from the CDI to the spark plug itself. The wire in the CDI or plug might of been having interment contact, and that caused the CDI to die. You could use bare wire from the CDI to the plug and run the engine..it will be a shock hazard but will run.

ok, ive had a fair few motorbike style cdi units fry on me from not using a proper boot with resistor. these are the types with a charge coil and a seperate trigger coil, and a few more wires...4 or 5.

its to do with back emf caused by the spark, that upsets something.

but!

ive rarely seen a simple 2stroke cdi thats required/used an insulated boot...

i thought i had this exact problem myself as my boot had recently collapsed.

upon investigation...these things have me scratching my head really hard...

i believe the HT motors are what i would call a zbox... with three wire systems. black, blue, white.

originally, as instructed, it was black/black, blue/blue(the only two to the cdi/coil) and white/killswitch.

one day, it suddenly stopped, a mile from home. nothing down the first hill... second hill i tried PRESSING the killswitch...it started! wtf? killswitch is still fine, btw. not suddenly reversed its operation.

so earthed the white wire. which has been fine, albeit a slightly weakened spark, until my boot fell apart.

this time it was a 20 km ride back home, with me pushing boot down onto plug! i tried just sticking the wire onto the plug, and hey! it got worse, until... i pedalled the least 2km (dont throw old boots over your shoulder)

got home, changed boots, and its been running yes, but not very nicely, until my newly ordered cdi arrived.

slightly improved, but white still needs earthing...and i said SLIGHTLY improved

leaving me with the sneaking feeling its actually the pickup coil on the flywheel thats the problem.

ive resoldered those wires and got 34 ohm across the coil, and 2M+ to earth at either end...normal? iunno. ordering a new one of them too, now...

but, I DO NOT GET HOW THESE CDI UNITS WORK! especially if the white wire was not connected to earth in the first place... unless there is an internal connection to ground (tap)in the pickup winding. which my multimeter says there isnt.

if there was, i get them. if there wasnt.... wtf?

the failure of such a connection does explain why my white wire now NEEDS to be earthed...

look at it this way. blue comes from the pickup coil. provides charging power for the cdi. black is earth. where does the other end of the pickup coil go to complete a circuit? apparently, the white wire. but thats the kill switch when earthed! so, therefore, there must be an internal tap.

THEN the system starts to resemble a chainsaw unit, that has been cut in half, and has the other half in that little black box...

arrrgh!

iunno. all i wanna do now is make a new flywheel, then machine the case to mount a chainsaw cdi unit, with the added benefit of a heavier flywheel then i can adjust the timing

 

[GearNut]

HeadSmess, Here's a schematic. I hope it helps you out.

 

[Wisski]

Gearnut - It's not the joint that's the problem (Since problems started, I've solder-sucked that joint out anyways, and re-soldered). From laminate frame to the point where the coil's ground exit the plastic holder, it's a totally solid, 0 Ohm connection. BLUE->Ground is around 35 M Ohms (Big Problem). BLUE->WHITE is about 350 (These turns are OK!). The ground wire itself is probably broken off somewhere inside the coil, where I can't get to it to repair.

Which isn't surprising to me - it looks like the electrical sadist errrr...worker, used a 4000 watt soldering iron to make the joint. Burned the insulation off the wires, at least down to the casing (I'm not inclined to unwrap the windings just to see wtf this idiot did). I don't know if it was just the current pull across unrated wiring, or the "worker" and his mini arc welder, but my ground wires CRUMBLED at the joint when I tried to re-solder. I had to carefully solder them to a rated wire, and then solder THAT to the laminate.

Al - At least on mine, that's just a solid connection point. There's a separate wire coming out of the white plastic case that holds the windings, and is soldered to the laminate, grounding it, and the entire engine case.

HeadsMess -

leaving me with the sneaking feeling its actually the pickup coil on the flywheel thats the problem.

ive resoldered those wires and got 34 ohm across the coil, and 2M+ to earth at either end...normal? iunno. ordering a new one of them too, now...

I'd say not. When my coils ground connection is acting up, it's around 340 ohms BLUE->WHITE, and anywhere from 19-35 M Ohms between BLUE->Ground and WHITE->Ground, indicating that there's a poor, or non-existent connection to ground.

but, I DO NOT GET HOW THESE CDI UNITS WORK! especially if the white wire was not connected to earth in the first place... unless there is an internal connection to ground (tap)in the pickup winding. which my multimeter says there isnt.

There is a connection to ground - There should be a few tiny wires coming out of the top/bottom/side of your generator coil, connecting to the steel laminate (It may be on the OTHER side of your coil!). The solder joint connecting your coil to ground is probably failing like mine was. GET IT SOLDERED SOLIDLY BACK ON NOW - otherwise you run the risk of the wires stressing INSIDE the coil, and breaking...like mine has.

the failure of such a connection does explain why my white wire now NEEDS to be earthed...

look at it this way. blue comes from the pickup coil. provides charging power for the cdi. black is earth. where does the other end of the pickup coil go to complete a circuit? apparently, the white wire. but thats the kill switch when earthed! so, therefore, there must be an internal tap.

Yup. Blue is about 90% of your windings, and white is tapped somewhere around the 10% mark. White is NOT a kill wire. It is an accessory power line, so you can run lighting/electrical (lol, in theory). Your kill switch should be replaced with a waterproof toggle switch (or a keyed ignition switch!), and spliced into the blue wire, and placed somewhere easily accessible while riding!

I'll have to try doing this on purpose on my bike...My ground is utterly demolished, so its either peddle till I can get a new coil, or turn white into ground. Thanks for sharing this - I probably wouldn't have thought of this on my own!

*gets the soldering iron heating up!*

 

[Wisski]

OK! Soldered WHITE->Ground. Took her around the neighborhood (I LOVE mine - 2 high grade hills, and about a 1/2 mile of straightaway). Peppy acceleration, good power (20-ish mph WOT) on a 20 degree and 30 degree hill, and almost 30mph on the half mile. Sounds like she's hitting every stroke. No bogging at WOT. This is a VAST improvement over the failing ground connection. I LOVE IT! XD

Many thanks to you Heads, for sharing your problem. Helped me fix mine till I can get a new coil!

 

[HeadSmess]

thanks gearnut 2 seconds of looking at that and there it is! the elusive ground tap right there on the magneto, as i suspected.

clears everything up.

and no probs, wisski sorta only found it out by accident anyway...why would anyone try using the killswitch to start something?


and and and, this means i can actually have a rectifier etc and run a few fancy LED spotties? phwoar!