Help CDI box tribbles

[drbone641]

Hi folks, new here but I know where you go when you need help. Owners on forums.
I have an 82 XS400 that is to be my sons first bike. It was my dads trailering bike and it has about 9600 miles on it. It started cutting off after about 10 minutes of riding. Short cool down and it would restart. I went thru everything fuel/wiring etc and traced it to the CDI box. I bought one off of ebay, put it on and presto. Running bike. Rode it for about 35 minutes with no problems and a bit more pep it seemed. Called my son to come over and go ride with dad. The bike had no spark at all. Put the old box back on and it fired up. WTF??? Did I just get the last 35 minutes out of a good box or is there a gremlin that I need to know about. Thanks in advance.

 

[drewpy]

mmm fuse box methinks, fusues will look ok, but move them around .....

 

[Hornix]

Maybe you have aging coils? They work fine with cold engine but when it warms up they fail. Also check the ground connections. The connectors should be sprayed it with contact spray. And a spare CDI is always good
And speaking of Gremlins...Never ever give your CDI water, especially after midnight

 

[hmusket]

Tribbles can be very troubling.

 

[drewpy]

I knew exactly what you were posting hmusket before i clicked!

was tempted meself

 

[drbone641]

Wow, Incredible bank of knowledge I tapped here.

 

[hmusket]

Check the coils, or coil, like Hornix said.

Maybe you have aging coils? They work fine with cold engine but when it warms up they fail

Our wealth of knowledge is limited to our experiences and the experiences of others we come in contact with. We gain it directly and through relentless searching and experimenting.

What is the resistance of your coils, are they within specs so you can rule that out as a possible problem? What made you decide the CDI was defective? Did you try the box again that you purchased from ebay? Did you check the charging system of your bike? Is it putting out 13.5-14.5 volts?
Information in-Information out.

 

[lhaolpa]

Ditto what was said about the connectors.I remove them one at a time,and with a soft brass brush,clean the male,spray the female side with contact spray,then put a little di-electric grease,then reattach. Also do the same with the fuses,anything that may be suspect.I make it a habit of looking for corrosion,as I find it everywhere it seems.....lha

 

[drbone641]

Now we're talking. Thks. I did exactly that so far. We went thru and cleaned and checked every connection on the wiring harness and inside the headlamp especially. The coils were the first suspect and they both checked good. When the bike would stop running, spark stopped to both sides. This also helped eliminate the coils. The fist effort to crank, after the CDI was replaced was succesful. The bike was idled for about 15 minutes, which was impossible before. Then it was ridden on 2 10-15 minute runs, and finally on a 35 minute jaunt. It sat overnight and would not crank again. I then switched back to the old CDI and the bike cranked immediately, but ran poorly as before. Now my question is , Is there something that can be killing the new box, that only injured the old one or is the consensus that the box I bought was about dead. I bought it on ebay and the seller has since told me it had been in a box for a few years.

 

[lhaolpa]

I would have the old box cleaned up and recoated with more modern materials.I read somewhere about shops that rebuild PCMs for cars,which would be about the same thing as a cdi box. However,you bought a NOS box,from what you're saying that doesn't work.Although that is possible,I would suspect something else,such as charging[low current situation] when running.maybe you could get an inexpensive voltmeter and hook it up temporarily,and run around close to home,and look at the charging current through the range of RPMs......lha

 

[drbone641]

Not NOS but used and recycled. The charge current idea is next tho. Could be overloading the box???? Then what I don't know. Rectifier????

 

[drbone641]

Fixed!!! The replacement CDI box was bad, so, after checking the voltage to make sure the rectifier/regulator wasn't overcharging I put a tested CDI box on and VOILA. music. Runs great now.

 

[drewpy]

good to hear, nice one