Zong CDI Failure at 41,800 Miles

[FastDoc]

What would be the advantage of a programmable CDI? Why do they fail so often? I assume you have to replace one of the tiny electronic gizmos? how the heck do you know which one?

I have been SOUNDLY outgeeked here. :wink:

[Weldangrind]

That's just basic four stroke care and feeding. As RPM increases, the point in time where the spark occurs (measured in crankshaft degrees) needs to advance. IOW, as the engine spins faster, the spark needs to light sooner, so that complete combustion can occur. It's a delicate dance, because if you start the spark too soon, complete combustion will try to drive the piston down while its still on the way up. We all know the sound of detonation; it's much like rocks in a coffee can.

A programmable CDI allows you to tailor the spark curve to meet the needs of a specific engine. BTW, your XR250R likely has a mechanical advance system that works with the CDI, because that's how they did it back in the day. As RPM increases, weights swing out when enough centrifugal force is applied to overcome the spring tension. Timing is then advanced to match the needs of the engine.

I played with the weights and springs in a GM HEI distributor once, and I got remarkable results. Not only was there a seat of the pants increase, the fuel economy jumped by about 40% (the car was regularly driven very hard by a buddy of mine).

[katoranger]

He went from 5 to 7 mpg. :wink:

[MICRider]

Originally Posted by katoranger

He went from 5 to 7 mpg. :wink:

Lol! Sounds like my big block 71 Firebird!

[SpudRider]

Originally Posted by Weldangrind

It never even occurred to me that we could dismantle the Honda boxes for repair. Excellent news! I wonder if the old two-smoke Yamaha CDI boxes are repairable; that was the achilles heel with those bikes; replacement CDI boxes are hen's teeth.

Thanks Spud!

You're welcome, Weld.

Originally Posted by FastDoc

...Why do they fail so often? I assume you have to replace one of the tiny electronic gizmos? how the heck do you know which one?

I have been SOUNDLY outgeeked here. :wink:

The DC-CDI unit of the XR650L is one of the bike's problem areas. Circuitry inside the box steps up the 12 volts from the battery, but this operation makes the CDI unit run hot. :roll: Repeated cycles of heating and cooling produce degraded, cold solder joints, which fortunately, can be repaired.

Spud