bad CDI symptoms?

[elbandtioCA]

hi folks, I've read a lot about fixing/replacing the CDI box when it goes bad, but I'm wondering if anybody can tell me the symptoms of a bad box.  I've got an ignition problem but I don't want to hack open the box and screw with the circuit if it isn't actually the CDI that is causing a problem.

i'm only getting an intermittant spark.  the carbs also need to be cleaned--the float valve is screwed up, so that is adding to the problem, but i know that even once I rebuild the carbs that there is a spark problem because I pulled the plugs and found that it only sparked *sometimes* when i cranked it.  when it wasn't sparking the coils were getting less than 12v--is this a symptom of a bad CDI?

also, will a bad CDI affect engine performance once the motor is running--like really rough, uneven acceleration at low RPMs, or does a faulty CDI only affect starting the bike up? 

if you can't tell i'm not an electrical pro...your help is much appreciated.  or if you know of a post that talks about CDI symptoms, or ways to test the box with a voltmeter before pulling it apart...

[tomacGTi]

Generally a bad CDI won't fire at all since everything goes through the box to fire the motor. Since you still have fire, I would rule that one out.

-Check to make sure the ignition leads aren't shorting. A spray bottle of water misted on them will confirm. If you need to replace them, you can just twist them out of the coil and the leads to the plugs.

-Check the leads that go the coils. They have spade clips on them and sometimes the wires fray or the spades loose their grip. A little squeeze and some dielectric grease goes a long way

-Check the rectifier/regulator as well to make sure it hasn't cooked your battery. Intermittant acceleration at low RPMs means that there might not be enough juice to charge the coils to fire the motor. Search for posts on this, Stormi had alot of experience with this one.

-Check the plugs themselves, the carbs flooding out may have carboned them up so much that they can't fire through. This could also be your rough running issue.

Try the basic stuff first and go from there.

-Randy

[StangMATA]

A CDI is either good or bad. Very rarely is there any in between.

[elbandtioCA]

thanks for the input.  i'm pretty sure that part of my no-start problem is the carbs.  when  i got a spark it did start up for a second but it shut down because one of the cylinders filled with gas, which suggests a bad float valve.  i'm working ont he carbs. 

but the plugs are clean and i'm still having the intermittant spark problem.   the strange thing is that when it isn't sparking, the coils  are getting like 11.9v, so perhaps the starter is drawing too much? 

which ones are the ignition leads that you suggested that i check, randy?  is that by the ignition switch, or by the signal generator coil, or by the ignition coils? 

i was curious about the faulty CDI because i read in one of these forums that someone said he had to crank his bike for a long time to get it started, but when he replaced the CDI capacitors it fired right up.  if that really was the case it sounds like the faulty CDI still produced a spark, but only sometimes.  if it isn't a big hastle maybe its worth fixing the cdi anyway, as a precaution for when it does go bad...

thanks

[PitterB4]

Are you loosing spark to all 4 plugs at the same time or is it just two off the same coil? 

If the latter, it sounds very much like the coil leads.  The wires from the harness that go into the coils have crappy spade connectors that stretch out over time and can make intermittent connections.  Like Randy said, pinch 'em, put some grease on 'em and see if that fixes it.  (He suffered through an entire day of riding with me alternating from two to four cylinders!)

[elbandtioCA]

i need to check to see how many cyls aren't firing.  so far I only looked tried cranking with one of the plugs pulled.  but because it wasn't starting at all --not even catching, i'm guessing that all 4 aren't firing at the same time.  well, i'll check to make sure.  thanks.

[interfuse]

As others have said, the CDI either works or it doesn't. With intermittent spark on all 4, I'd be looking at the pickup wire. Try jiggling the wire that goes into the left hand side engine case and try starting it. If you've only got intermittent on 2 cylinders then look at the 12v wires going to the coil pack for those cylinders.

[pmackie]

the strange thing is that when it isn't sparking, the coils  are getting like 11.9v, so perhaps the starter is drawing too much? 

Make sure your battery is in good shape, and fully charged. A weak battery can cause intermittant spark when cranking.

[elbandtioCA]

hey guys--i'm back on here, with the same problem.  maybe you could advise a little more...before i could sort the problem, the bike stopped running at all so i took it to a (highly recommended) mechanic.  it didn't even have a spark at all.  when he checked it out, he found that the carbs needed to be rebuilt (the float valve was broken and the cyl filled with gas).  he rebuilt them ($$$)  then he diagnosed the ignition problem at the signal/pickup coil, which was bad.  he replaced it.  the bike fired right up...and ran exactly like it ran before--like crap.  weird acceleration at low rpms, then total lack of throttle response even if you open it all the way, then it revs all the way up and seems to be fine for ten seconds or so, then it cuts out.  it gets worse if it warms up--then you can't even get it to rev up at all. 

so the bike is at his shop and i can't get it home, but he seems baffled.  i haven't gone through and done all the checks that randy suggested with the regulator, but i think that the mechanic checked out the connections when he diagnosed the signal coil.  if it runs at all, does that rule out a bad ignition coil, or lead?  the battery is good and it is fully charged up.  so i'm back on here wondering about the this CDI thing again--the mechanic admitted that it might be possible but he didn't have much experience with black boxes going bad.  a few people on here suggested that their bikes were running poorly and then ran better with a new CDI, so now i'm wondering if it could be the problem afterall--despite what a few of you said (i.e. either it gives a spark or it doesn't, nothing in between). 

sorry if this post is redundant...i'm just in a hard spot because the bike is at his shop, it won't run well enough to get it home, and i can't really do all of this electrical trouble shooting while he has it.  and moreover, i know a hell of a lot less about bikes than he does so i don't feel like i can suggest things for him to try.  if the CDI is even a possibility, that seems like an easy fix because i can pop it off the bike get it fixed, and plug it back in.  i'm just wondering if there is anybody who DID have these symptoms and solved them with the black-box fix...