I would say the answers to your 2 questions are: Yes, and Yes.
The Bandit CDI boxes are Denso Corp. products. They are pretty good quality but the capacitors that were used in their construction are their weak link. Capacitors age and dry out and eventually cease to function. Then you're left with a Bandit that might be perfectly fit to run but won't because of a few capacitors.
It has been proven that a moderately skilled individual can open up a Bandit CDI box and identify the capacitors, then remove and re-solder new ones. Here is a link to a very old thread here on the BanditAlley.net forum which was a discussion between members about how to do the capacitor replacement:
http://forums.banditalley.net/index.php?topic=431.0If you have a dread fear of electrical work and/or no knowledge of the subject then you could always have a qualified electrician do it for you.
Yes, you could search around on sources like Ebay for a replacement CDI but it will be the same age as the one you already have which might mean its capacitors aren't very far from giving up the ghost, and then you're back where you are right now.
I think you may have made a very good call by taking the swap. It sounds like this new Bandit might have been taken out of service by a simple CDI failure which means it might be very sound and ready to run otherwise.
Good luck with the CDI fix, that's your first order of business.
Also, here's a quote from another BanditAlley.net forum member:
But ignitor may be faulty. Capacitors tend to dry out which decreases their capacity and filtering abilities. I have replaced them on one of my ignitors. This may / may not help.
Another problematic part of original ignitors are final stage high-gain bi-polar transistors which do all the rough work and pass quite a huge currents through ignition coils. These tend to raise their resistance over time which causes to generate more heat and in turn raise the resistance even more until engine stops to work. This causes smaller voltage/current to be applied to ignition coils and thus weaker spark.
Even if spark is present when plug is out of engine it may not be able to crank. Even with brand new plugs. I experienced this once when the only action which helped was to replace the final stage transistors with new ones.
Bad news is that current electronics is using unipolar transistors for high-current switching circuitry so there are no transistors available offering switching capabilities of original parts nowadays. IIRC original transistor had h21e (gain coefficient) of over 500. Current transistors which are available have h21e coefficient at best of 1/3rd of original. In my ignitor darlington-type TIP150 from fairchild worked well and provided enough gain to create spark which is able to run the engine (not only spark out of engine). It is also mechanically and electrically compatible so you do not need to adjust PCB/circuitry or change position of anything inside. Just desolder old and solder new.
If final stage transistors need to be replaced can be examined by connecting terminals to oscilloscope and read voltage between ignitor terminal connected to coil and ground during the phase when transistors are open. Ideally it would be 0 but as the transistors are old they build some resistance which in series with quite a low resistance of ignition coils causes voltage buildup on transistor. I cannot provide figures of what voltage is already bad and which is good but if voltage is different for left / right coil and / or if it is larger than 1V I would replace final stage transistors for new ones.
So this quote is pointing out that it could be that the problem is capacitors
Or it could be the big high-power ignitor transistors... or it could be both. The good news is that both of these items can be diagnosed and replaced (pretty easily by somebody who had the knowledge and skills)
Topic: Bandit 250 project problems (Read 11390 times)