CDI?

Is the CDI toast?

No - there is a bad ground or something as the starter won't turn very well. Grounding post shows signs of tarding. Also, there is some spark even though the coil cap seems crappy.

Yes - There is weak spark. It failed for PO suddenly on the road. There is a melted-looking place in the cdi potting. It's old and why not. Also, the unit fails all the tests from the book - infinite resistance everywhere except between the two E posts.


Here's some wisdom from a forum:
"FYI, the CDI unit is known to fail unexpectedly, especially in older machines, not just Hondas but all bikes/scoots. They can also create irregular performance before complete failure. Buying a used CDI has the risk of short life, and there is no way for the backyard tech to test other than to observe a running engine before removal. There are a few clone CDI's made in China that are just as good as OEM, and are inexpensive, but shop around as the price varies.

The CH250 1985-1988 series uses an AC type CDI, where the 89-90 use a DC type, and they are not interchangeable. For scoots running one day and not the next, the CDI should be on the suspect list."

To tell if you have a DC or AC CDI look at the plugs. There will be a 4 connector plug and a 2 connector plug. On the 2 connector plug, if there is 1 wire then it is DC, if there is 2 wires then it is AC."

Pardue Brothers how-to on testing the CDI on a cub 70.

Another forum link with a CDI issue on a CH150 (same basic motor).