No Spark When Hot
I'd had previously asked for the transcript from the Piston Ported guy tech session at the Jamboree in KY. Someone said they'd add it to something on the site, but I don't know where, or if that happened. Did it? I can't even find my question or where I posted it. Anyway...I wasn't asking for shits and giggles.
I was asking because my newly ground-up built 64 LI125/BGM195/Clubman Sport setup ran like a champ at the Jamboree. It ran fine for a few outings once home. Then out of the blue it died within a minute down the road. No spark (physically verified by pulling it). Spark returned after the engine was cold, so I hoped for a loose/bad cap wire/cap. Since the Casa Lambretta Ducati 12v electronic ignition kit parts are not readily available or cheap, I replaced the plug, cap, and spark plug wire.
It started, then died in the same exact spot the next day down the street after replacing those things. Same thing, no spark. So those parts were not the issue, as I assumed.
Between web searches and the the Casa Lambretta USA guy in CO, I found meter testing measurements for the stator and meter testing measurements for the wiring other than ignition. The stator and other wiring tested good.
I never did find out how to specifically test the Casatronic CDI with a meter. Does anyone know how to do that?
Apparently, sometimes you just get a lemon CDI or your CDI isn't adequately grounded (which the Piston Ported guy mentioned), and in both cases causes it to fail when it gets hot.
I bought a new Casatronic CDI from Cambridge Lambretta and added another ground. That fixed it and it's been fine for an additional 10 plus hours of riding since then.
My question is how to test the Casatronic CDI (which obviously failed), and what testing variables are there between the various types of electronic ignition components/manufacturers.
Any clarification would be appreciated.
Hey Robert, I will post it when I have it finished as my notes were very short hand bullet points for the tech session but to answer your question:
Basically I don't think CDI testing is reliable with basic tools and a multi-meter. The way I train it for technicians at my job is to basically test everything coming into the CDI from the stator and test everything after the CDI. If everything tests out on the stator side and everything between the cdi and the plug test fine, then it's the CDI. The CDI tests up and the dies. It can and will come back after it cools off enough to do it's job. Another tell is if you put a new plug in and it magically runs then dies a few blocks away, that's because the new plug offers less resistance since it's cold. As soon as it tests up and the resistance becomes too much for the cdi to overcome, it dies again. That's usually within a half a block. I use that as a tell but always advise verifying the stator with a multimeter before just slapping a new CDI in because nobody wants to push a bike home.
You verified the stator, it passed. The ground side of the stator was a problem on early casa kits as the anodized blue coating interfered with it's abilit to create a good ground between the stator and the engine case.
The only thing you could have done is unscrewed the plug wire and measured for continuity between the end of the wire that screws into the cdi and the terminal inside the plug cap but I'm not sure those wires even come out on those CDI's so you did everything you could to diagnose it.
Funny story, my brother's Vespa stator with an Indian K2 pickup coil dies while we were in Kentucky and I had to walk him through all the tests. We replaced it with an OEM piaggio pickup coil after I got back and it's back to being a 1 kick bike.
The only thing I still need to do is get photos of the tests. I'll roll one of mine on the bench in the next week or so and grab those. It'll be published in the specialist mag with a PDF download available here.