Bandit won't start

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Carlr337
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Bandit won't start

Post by Carlr337 » Mon May 25, 2015 6:56 am

Hi
I wonder if someone can please help? I have had my Bandit (400VC) for 2 years now, and it was running with no issues at all... That is until about 2 months ago when I was traveling on the highway and the bike lost all power and would not rev past 4000 rpm... I took the bike into a local workshop that specializes in carburetors ( I live in South Africa so we do not hae may garages that will work on carbs). He informed me that the carbs would have to be redone, after parting with my hard earned money, I received the bike back, and yep same problem bike would not rev past 4000rpm. I took the bike back and he had it for a month, paid again and same problem.

I though it might be the fuel tap checked and replaced, the bike would start idle for about 5 minutes and then cut out, now the bike will not start at all?? When i try to start it, it all most seems like it wants to kick over will backfire and nothing. I have replaced the plugs and tested that there is a spark, and they are wet when I remove them....

I purchased a complete bike on the weekend with a blown motor, and took the carbs for that bike, and same problem..

Please could someone advise me on what I could so?

Thanks

SevenThreeSeven
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Re: Bandit won't start

Post by SevenThreeSeven » Mon May 25, 2015 4:00 pm

I'm willing to try (to help)... although, fixing a motorcycle over the internet isn't easy. It's more like trying to solve a mystery novel after only reading one or two chapters.

From your 1 post asking for help here in the forum there's only one word that strikes me as being a real clue, and that word is "suddenly". Things don't go wrong with carbs "suddenly". Things go wrong with carbs gradually, often happening quietly in the garage when the owner allows the bike to sit unused and idle for a while. So when somebody describes a situation where a bike loses power or quits during a ride we (the forum members) don't immediately suspect the carbs.

Of course, there's always an exception to the rule, and the exception to the rule (that things don't go wrong with carbs suddenly) is water. If water has gets into the fuel tank and then into carb float bowls there will be a sudden problem.

Back to your description of the on-the-road malfunction: You don't exactly say it but it sounds like you're describing an engine that very suddenly went drastically down on power, but would still run. Is that correct? Did the bike continue to run even though it was severely down on power? Did the engine note change? Did it sound like it was only running on 2 cylinders rather than on all 4 cylinders?

If so, it sounds like an ignition system failure because the ignition system on the B400 is divided into two halves, one coil runs cylinders 1 & 4 and the other coil runs cylinders 2 & 3. When you lose one of the bike's two coils the engine will still run but only two cylinders will fire.

So I'm inclined to point toward an electrical problem of some sort, a problem that is almost certainly to some degree also heat-related in its failure mode (at least in the original event you described).

Contained within the B400's electrical system are several components that don't always age gracefully.

First on that list of age-related B400 electrical woes is the Ignition Control Box. Inside this box is a circuit board and there are capacitors soldered onto that circuit board that are known to "dry out" over time (age related degeneration) or "blow out" under stress (like when somebody connects a running car to the bike's electrical system with jumper-cables).

Also contained within the Ignition Control Box are two Coil Driver Transistors (one for each of the B400's two coils). These coil driver transistors are also known to die of natural/unnatural causes. The Coil Driver Transistors are the part of the Ignition Box that has to deal with the stress of grounding the 12 volt power flow that charges the coils during "dwell" and with what amounts to a brief but fierce electrical storm backlash when the Ignition Box breaks the ground to the coil which fires the spark plugs (first the electrical field in the coil's primary winding collapses which induces a huge field collapse in the coil's secondary winding which grounds through the path of the high-tension lead to the spark plug electrode).

I know, the non-electrically-skilled owner's first thought is, "I'll just find another Ignition Box cheap on Ebay and do a quick remove-and-replace job." Yes, that's an idea that could work for you, but the problem is that the Ignition Control Box you source off of Ebay is old too, and there were several versions of the B400 Ignition Control Box (early B400, late B400, and Variable Valve B400 + Ebay sellers aren't known for the accuracy of their inventory descriptions).

The good news about the Ignition Control Box is that somebody with only moderate electrician's skills and knowledge can disassemble the box, remove and replace the circuit board's 5 capacitors and 2 coil driver transistors, then reassemble and seal it again and it will be as good as new.

Another item whose failure could have caused the initial problem you described is one of the bike's coils. Coils can go bad over time. They naturally heat up during operation. These heat-cycles will age the coil until one day it just stops performing

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Re: Bandit won't start

Post by Variablevalves suck » Mon May 25, 2015 7:00 pm

Ye sounds like an electrical problem,
Possibly a bad coil but check the wires that connect to them first, low tension (thin) and high (thick) check everything is tight.
Next check the pick up trigger resistance, download the manual off this website and it has the procedures with readings.

Another common problem with the VVC is the VC solenoid, it sits under the rear panel and looks like a bigger version of the indicator relay that is under the opposite panel, these get a load of water in them, ive had two go down and now re house them under the rear seat, you find one of the 4 connectors gets heavily corroded and give allsorts of weird problems.

If the CDI has gone bad you have problems because you can't pull it open like the standard b4 because they decided to fill it with foam from the factory so even when cut open its just a block of hard foam.

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Re: Bandit won't start

Post by SevenThreeSeven » Tue May 26, 2015 2:44 am

If the CDI has gone bad you have problems because you can't pull it open like the standard b4 because they decided to fill it with foam from the factory so even when cut open its just a block of hard foam.
Interesting...

I wonder what a dip in Acetone (or a 50/50 Acetone and Methanol mix) would do to that hard foam? I'm pretty sure Acetone wouldn't harm the silicone circuit board or the components soldered into it.

If if turns out that the Ignition Control Box is officially diagnosed "bad" what's the harm in the experiment of cleaning the hard foam off it? Maybe the thing could be saved.

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Re: Bandit won't start

Post by Variablevalves suck » Tue May 26, 2015 8:09 am

Could work, its the same with all the 12 pin boxes, so gsxr4 sp also.
In fact the VVC runs using the sp cdi but only in high cam mode.

Carlr337
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Re: Bandit won't start

Post by Carlr337 » Fri May 29, 2015 3:53 pm

Hi

Thanks for the advice I will look at it tomorrow and let you know.


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