FAQ
TL;DR: On Loncin 250cc no‑spark faults, “thin wires break off” and about 50% trace to the CDI power coil; the other 50% are modules. Focus tests on the pulser and the stator’s CDI feed. [Elektroda, rafcio_21, post #16637334]
Why it matters: This FAQ helps DIY riders quickly isolate no‑spark causes without guess‑replacing parts, saving time and money.
Quick Facts
- Reported healthy readings: charging coil ≈300 Ω and pulser ≈141 Ω on this model. [Elektroda, lisekey, post #16637213]
- Typical wiring noted: black/red = CDI power, blue = pulser, green = ground, white+yellow = charging. [Elektroda, lisekey, post #16637317]
- Black/yellow wire carries CDI output to the ignition coil; erratic voltage observed during cranking. [Elektroda, lisekey, post #16637213]
- Field experience: ~50% failures are CDI power coil breaks; ~50% are CDI modules. [Elektroda, rafcio_21, post #16637334]
- A grounded kill/stop wire completely suppresses spark; disconnect to test. [Elektroda, rafcio_21, post #16637244]
How do I quickly pinpoint a no‑spark on a Loncin 250cc?
Start at the trigger and source. Load‑test the pulser by briefly touching its lead to engine ground while cranking; you should see a spark. Repeat a load‑test for the CDI power coil; meters can pass bad coils. If both pass, inspect CDI and coil. [Elektroda, rafcio_21, post #16637387]
What does the black/yellow wire do?
It links the CDI module to the ignition coil’s primary, carrying the discharge pulse. In this case, the poster saw fluctuating and even negative readings after cranking, pointing you to the CDI‑to‑coil drive path. [Elektroda, lisekey, post #16637213]
Which stator wires power the CDI and sensors on this quad?
Reported mapping: black/red supplies CDI power, blue is the pulser (pickup), green is chassis ground, and white plus yellow feed the charging circuit. Verify colors on your harness before testing. [Elektroda, lisekey, post #16637317]
What resistance values suggest my pulser and charging coils are OK?
A user measured about 300 Ω on the charging coil and 141 Ω on the pulser. Treat these as typical reference points, then confirm performance with load tests, not just a multimeter. [Elektroda, lisekey, post #16637213]
Why does my multimeter say the stator is fine but there’s still no spark?
Some coils fail only under load. “The meter shows that it is ok, but it is linden under load.” Do live cranking tests on the pulser and CDI power coil to reveal intermittent or weak output. [Elektroda, rafcio_21, post #16637387]
How common are CDI versus stator failures here?
An experienced tech reports roughly 50% are CDI power‑coil breaks at the fine lead connection, and the other 50% are CDI modules. “Thin wires break off,” so inspect that junction closely. [Elektroda, rafcio_21, post #16637334]
Could the kill/stop wire be the entire problem?
Yes. If the kill wire grounds the CDI, there will be no spark. Disconnect the extinguishing lead at the module, then crank to check for spark. Reconnect after testing. [Elektroda, rafcio_21, post #16637244]
If the pulser (pickup) fails, what symptoms should I expect?
You may still get a spark, but not regularly. Irregular trigger signals cause random or missing sparks during cranking and running. Confirm with the simple ground‑touch pulser test while cranking. [Elektroda, rafcio_21, post #16637387]
Which stator coil should feed the CDI, and can miswiring kill spark?
Feed the CDI from the larger dedicated power coil. Misconnecting charging coils as CDI supply can prevent spark. Re‑trace the two engine leads for CDI input and the single CDI‑to‑coil lead. [Elektroda, rafcio_21, post #16637307]
Will a 110cc quad’s CDI fix a Loncin 250 no‑spark?
Not necessarily. In this case, installing two known 110cc CDIs did not restore spark on the 250. That points back to wiring, the stator power coil, or kill‑wire issues. [Elektroda, lisekey, post #16637342]
What is the pulser (pickup) on this system?
It’s a small trigger coil that senses flywheel position and sends a timing pulse to the CDI. Without a clean pulse, the CDI won’t discharge correctly. Test it by the brief ground‑touch method during cranking. [Elektroda, rafcio_21, post #16637387]
I see ~12 V on the black/red CDI power lead; does that rule out the stator?
No. The poster saw about 12 V on black/red yet still had no spark. Suspect a weak CDI power coil under load or a faulty CDI despite the static reading. Load tests are decisive. [Elektroda, lisekey, post #16637342]
How do I load‑test the pulser and CDI power coil (3 steps)?
- Disconnect the pulser lead and briefly tap it to engine ground while cranking; watch for a spark.
- Repeat with the CDI power coil lead; look for a spark response.
- If either fails, inspect wiring breaks at the coil lead junction and replace as needed. [Elektroda, rafcio_21, post #16637387]
