Bandit 400: Is my CDI bad?

[SoEazy]

Hey guys,
A little background on my Bandit. I sort of inherited a 1991 Bandit 400 that has been sitting in a shed for 10 years or so. So far I have thoroughly cleaned the carburetors and replaced the o-rings. I have replaced all spark plugs and have been using a remote fuel tank for testing because I think my petcock is bad.

I can get the engine to start but it will only do so intermittently. There seems to be no rhyme or reason to how and when it starts. It ran for 30 seconds or so after spraying starter fluid in the carbs. Otherwise it will only sputter or run briefly. I've checked each plug and am getting spark. I can drain fuel from each bowl, so I think the carbs are getting fuel. I've checked the coils and they appear okay. I've checked the spark sensor and it checks out.

Does that rule out everything but the CDI? What else is left? I'm running out of ideas.  The clutch switch is bypassed and the sidestand switch is also working properly. I'm ready to ride this thing! Sounds mean when it starts!

[SoEazy]

Hmmm... not a ton of action on this forum eh? I want to also add a few things to my previous description in case anyone wants to jump in. I am planning on checking compression this weekend. I noticed after running the engine for 30 secs. or so that all pipes were hot to the touch except the no. 4 cylinder. However, the engine seemed smooth when it ran.

As far as the carbs go, I wanted to give a little more detail there as well. I've changed all o-rings except for the emulsion tube and pilot screw rings. I am planning on replacing them when I remove the carbs again. I had to remove them from the bank in order to soak them in cleaner individually. The pilot screw is currently 3 turns out. Also, when it ran the airbox was off so I could spray starter fluid in the carbs.

Finally, the CDI. Because the bike will start, although really difficult, does that mean that it has to be good? I'm not sure if it is possible for it to function part of the time?

Thanks for any help guys! I've already learned a bunch from this site. I hope to be riding soon. 

[tomacGTi]

If the bike runs and starts: it's not the cdi. It wouldn't even fire if that were the case.

[SoEazy]

If the bike runs and starts: it's not the cdi. It wouldn't even fire if that were the case.

That was my understanding too. Except that I've read other members post about the bike being difficult to start and the culprit being blown caps in the CDI. Anybody able to chime in on this? I'm not sure if it's possible for it to work part-way or intermittently. I guess I'll be going back through the carbs again....

[Nickelodeon]

I'm with tomac, if you can keep the bike running with starter fluid it's not the CDI.

[Chris H]

You answered you own qustion when you said it runs cool on one pipe.

Its only running on three cylinders, add to this the fact that the airbox is off and you got a non runner.
First thing i would do is clean the pilot circuit of the bad carb and then fit the airbox.
The B4 is very sensitive to carb settings.

[SoEazy]

Okay, after cleaning and rebuilding the carbs, it appears the CDI has died. The bike no longer gets any spark from either coil. I've checked them both and appear to be within spec. I've also checked continuity on the pickup sensor and appears okay. What's the best way to open up the CDI? It appears to be molded as a single unit. Also, anyone have a good resource for purchasing all the parts? I'm not really sure what parts need to be replaced in there. Any help is much appreciated, as it seems one problem leads to the next. Guess there's no such thing as a free motorcycle...

[phoenix]

http://forums.banditalley.net/index.php?topic=431.0

[Sean]

That's weird. I didn't know that it was possible for the cdi to go partially bad.

[SoEazy]

http://forums.banditalley.net/index.php?topic=431.0

Thanks! That's the thread I was looking for. I'm going to try my hand a repairing the CDI. So ready to be riding this thing soon.