CDI Box Failure Mode

[blitz11]

Greetings.

After 7 weeks in a cast with a broken wrist, I was able to ride. On Thursday, rode 20 miles, bike ran great. Rode 25 Miles Friday, mostly 1'st - 2'nd gear tight stuff. Hit a fire road, opened it up, and it died.

Felt like no spark. Pulled plug, no spark. New plug, no spark. Towed to trailhead. Done for the weekend.

Yesterday, tested the bike. Stator measurements good (100 ohms pulsar resistance, 27 ohms exciter resistance). Spun motor with electric drill, see 35VAC at the exciter terminals, and 350mVAC at the pulsar (which i would expect as the RMS value will be low). I didn't have a scope or A2D at home, so i couldn't measure the waveform. But, on a gut level, it seems OK. No corrosion at the stator/rotor. Looks clean. Main bearing tight.

I plug everything back together, check and WA-LA! Spark.

What the heck? I kick the bike, and it starts, idles. I can't rev it up 'cause of the neighborhood, but it seems good.

Anyone seen a failure like this?

It doesn't seem (but could be) to be a heat deal, 'cause it went 25 miles before it completely failed.

I am going to build a arduino-based CDI this fall. That way I have a spare and won't stranded again.

That might be worth a tech article.

Any insight is solicited.

Thanks.

blitz

[GMP]

Blitz did you check the coil/HV wire? They come loose sometimes, I think because the upward direction of lifting the cap off the plug puts a counterclockwise torsion on the wire at the coil, unthreading it if its not bonded good to the coil body. happened to my '03. Also check your harness for damage where it can flex when you lift the subframe. Doubt its thermal, it would have restarted sooner than that.

CDI project sounds cool, multi map of course right?

[blitz11]

Hi Glenn,

The HV appeared tight at the plug. My buddy checked the coil side, but I did not. I'll double check that tonight. Thanks for the tip.

Multi-map, of course. The arduino board has a USB port, so I think that i'll come up with an excel-based advance curve tool so i can easily graph it on a netbook, then load it into the ignition. That way, people can interpolate between dry and wet ignition maps. I have the arduino board on my desk, but have yet to fire it up.

I am also going to use LEDs to indicate exciter signal, pulsar signal, and signal to the coil. That might help field diagnostics.

Thanks again.

blitz

[GMP]

Looks like a nice little system at a good price. Saves you the hassle of making a board for a PIC, or dealing with a much more $$, larger, and overpowered board for the application. Keep me posted. Design in a good power supply/filter, not the cleanest power available from what I have seen.

My guess is the stock mapping is crude, from what I have observed with a timing light and tach.

[blitz11]

Yes, this board makes it much easier than doing the board-up design and implementation. We've been controlling things in the lab with these, and they're really pretty slick.

As always, the power supply is the tricky bit. I have to get a scope on the exciter output to see exactly what that looks like, harmonic content, etc. But, these boards seem pretty robust, so we'll see where it takes us.

blitz

[Brian]

I could be interested in purchasing such a thing or throwing some bucks your way for the design....

I haven't played with arduino (mostly PIC and ARM), the whole hiding from C code thing sort of turned me off but it looks like a lot has changed since I last checked them out a couple years ago.

Sounds like a fun project, please keep us posted.

[blitz11]

No need to throw $$ at this yet. I have to make it work, first. That means making the time to do it. Nov looks crappy, but we're furloughed in December, so I'll probably make the big push then.

Thanks for the support. The pressure is on!

blitz

[motopsycho87]

I'd definitely buy one