Cold causing Honda CDI module failure. Why?

[Erbuck]

The replacement CDI module is on order, but I'm wondering if anyone has an idea why a Honda CDI module would fail below 55F?

Motorcycle: 1991 Honda Nighthawk 250

Symptom: no spark on cold mornings. Randomly cuts out when driving in cooler weather. Works fine on 70F days. Works fine for an hour or so if your warm up the CDI module in a toaster oven before driving on a cold day.

I was certain it was corrosion at the socket causing the problem, but the "toaster oven test" showed bad performance before heating, good performance after heating followed by declining performance (cutting out, stalling) as the CDI box cooled to outside temps.

The CDI module is sealed in epoxy or something and is solid state, so I just don't understand what would fail in a temperature sensitive way. Can anyone explain?

I got the idea to test the CDI box from a Honda Rebel site. They couldn't explain it either.

 

[ST Guy]

My guess would be a broken trace or solder connection on the PCB somewhere. When warm/hot enough, you've got the connection and everything works. When it gets colder, all the various materials shrink just a bit and it's enough to open up the gap/break and it then doesn't work.

When checking PCB's for faults, one of the tests is to lower the temperature of the suspect connection or circuit. If it fails with the lowered temp, a defect is presumed present.

 

[ST Guy]

If it's still under warranty, you should be getting a free one.

 

[Erbuck]

My guess would be a broken trace or solder connection on the PCB somewhere. When warm/hot enough, you've got the connection and everything works. When it gets colder, all the various materials shrink just a bit and it's enough to open up the gap/break and it then doesn't work.

When checking PCB's for faults, one of the tests is to lower the temperature of the suspect connection or circuit. If it fails with the lowered temp, a defect is presumed present.

The whole CDI unit is encased in epoxy or Lucite or something like that, so there's no getting at the circuitry to diagnose the problem or repair it. Your theory sounds reasonable. Its 20yrs old, so I assume the replacement OEM will be better (knock on wood) as its a model that is still made today.

 

[ST Guy]

Oh, I wasn't saying you should try to diagnose or repair it. 'Just pointing out a possible cause.

20 years, huh? Do you have an extended warranty?

 

[Randy B]

It could be a cold solder joint within the module. With all of the rattling and bumps these deal with its amazing that things like this don't happen more often.

 

[Ironbutt]

Hmm.. Look up Jerry Ellsworth creating her own dioads at home and she explains why solid state parts fail.

The material breaks down and creates more restiance becasue of dirt during the manufacturing process. The contaminated parts work but not as cleanly or do they react as fast.. this can be seen on a O-scope.

 

[ScottRNelson]

The CDI unit on the Honda XR650L is known for eventually getting cold solder joint open connections inside. It could be the same issue with your Nighthawk.

There is a guy in Nova Scotia to repairs them as a hobby and has documented the whole process on ThumperTalk. He digs out the stuff that seals it in, removes the solder from all connections, then resolders them all. He said that he's only seen two or three that he couldn't fix. The one I sent him happened to be one of them.

I bought a new one anyway and was just looking for a spare, so I wasn't too bummed that mine couldn't be fixed.


The symptom for mine was that I couldn't get the bike to start when hot. It was never a problem when cold. Until the bike was totally dead.

Some people have been able to fix the problem temporarily by banging on the CDI box. The best solution is to buy a new one (about $130), then maybe try your hand at resoldering it as a spare.

 

[ST Guy]

Too bad those things are likely not generic like VRR's. Otherwise you could use one from another brand/model.

 

[Erbuck]

This is where I ordered the replacement CDI box: http://www.dbelectrical.com/c-11555-honda.aspx

I'm not sure if it OEM, but its almost 50% the price of bike bandit. Likely imported from South America or India in bulk. The picture has the same socket as my original, but looks like a smaller box.

I realize I'm doing this at my own peril. Will report back.

 

[Erbuck]

Case closed.

Finally got the replacement CDI unit installed.

Did it on a cold morning. Started right up with the new CDI box.

New CDI unit was smaller, and not OEM, but clicked right in. Made in Argentina.

 

[wildwhl]

Good on finding a replacement CDI. I've repaired/soldered a few CDI's in the past. It can be a chore to remove the encasing epoxy but isn't that difficult, especially if you follow one of the writeups on the web.

Just a point to remember - if you're on the road and your bike suddenly dies/you suspect the CDI. Try squeezing it for a restart. Might get you home (has me on the NX650).

WW

 

[Erbuck]

Update....if you care......

TL;DR OP fixed (white text to right) a non-functioning CDI box. Didn’t need to, the replacement had been bought, but the OP can’t let shit go.

The aftermarket CDI unit failed after 200 miles (Me to girlfriend: "what the hell did you do?" Her: "Nothing!" Why it failed with her driving, when I had commuted with it and had generally beat on it with no problem, is something I attribute to Karma. At least the rescue was pretty easy).

I bought an OEM one ($150) and have had zero problems since. Even used it to diagnose another BARFer's (TT03gsxr) ignition problems.

That BARFer gave me his old CDI unit. I had given my old CDI unit to Smokey to try to fix. I asked for it back when the aftermarket CDI failed. So I had two extra CDI boxes to monkey with.

The aftermarket CDI unit guys were nice enough to give a replacement, but they don't refund for electrical stuff. I gave the replacement aftermarket CDI to the BARFer with the ignition problems (TT03gsxr, is it still working?).

So, this is the link telling you how to tear into your CDI module: http://www.ta-deti.de/ta/knownproblems.html#blackbox
This guy took the pictures I should have: http://www.thumpertalk.com/topic/881740-xrl650lnx250650transalp-cdi-repair/page-5
Apparently the Honda Transalp guys are the “repair it yourself” types.
The Transalp has same CDI unit. If the socket is the only criteria, a lot of Hondas use this CDI.

If the socket is the only criteria, fleabay has them for $7 – just search for CDI box.

The only way I had to test my soldering was on the motorcycle. I couldn't find any information where I could test it any other way. Having a working CDI unit is invaluable for this.

The CDI module I had received back from Smokey had received a lot of soldering attention, but I couldn’t help myself from fiddling with it a little more. I cut into the CDI module from TT03gsxr and did some solder repair where my magnifying glass said it needed it.

The CDI unit back from Smokey didn’t work. The CDI unit from TT03gsxr didn’t work after receiving attention from me and my soldering iron.

The breakthrough was when I saw a blue spark on the unit from TTO3gsxr when I tried to test it. The blue spark gave away the bad solder joint. Fixed that joint and the Nighthawk purred like a kitten. The original CDI box, the one Smokey had worked on and I had worked on still refused to work. I decided that the original problem was still the problem. I put it in the toaster oven. Heated it up to the point where it was warm to hold. When I tested this CDI box, the Nighthawk started but ran poorly (which was kind of a breakthrough). This CDI box probably has a bad capacitor and is beyond my ability to repair. It’s 22 years old after all.

Lastly, if you want to stick it to “the man” and build your own CDI module, here’s where you get the circuit diagram: http://www.scribd.com/doc/3565537/Make-Your-Own-CDI

So the lesson here is that you can repair your CDI box but it’s not as simple as the pictures on the internet. And its time consuming.

The other lesson is that can’t skimp on parts for your girlfriend’s moto.

 

[KrustyKruser]

Awesome! Thanks for the links. Definitely great reading material.