Bandit Alley
MODEL SPECIFIC => SUZUKI BANDIT 250 & 400 => Topic started by: t6nis on June 16, 2015, 03:24:31 AM
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Hi guys.
For starters this hasn't happen a lot, but it still gets me worried. Sometimes when i drive 2 cylinders fail, 1 and 4. I know what u are thinking, that it'd def. the coil, but i have tried it with another coil, the bike was standing tho, and it didn't change anything. The only thing that seemed to make a change in any of this is when i unplugged or plugged my CDI signal cable, or fiddled with the wires. The wire ends are replaced with new ones.
Are these signs that the CDI caps are going bad, or am i missing something?
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The best way to answer this is to get oscilloscope, wire it to both coils primary circuit (+12VBAT & wire from CDI to coil primary winding) and compare how far voltage drops on each one during recharge. In your case if outer cylinder coil's voltage drop will be significantly lower (which means that the voltage during recharge will be higher!) than the other, your CDI is eligible for final stage transistors replacement. I never saw CDI with blown capacitors so I cannot say how exactly it behaves but most probably the CPU would be unstable thus significant discrepancies in coil charge timing should be observed.
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Is there another way to do this, If i don't have access to an oscilloscope?
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you have no chance using digital and/or analog voltmeter... but if you are able to put together some simple circuit then analog comparator + voltmeter + adjustable voltage source + LED should let you roughly measure the voltage drop.
in extreme case circuit as simple as one LED with two resistors, one pot and voltmeter should allow you to compare voltages across both coils (due to limitations od LEDs you cannot get exact readings using this but simple compare should be enough for you to tell if CDI is OK).
edit: Above won't work. The circuit will effectively form bridge with so low impedance that the circuit either won't be able to light the LED or giving completely wrong output or drawing so much power something will burn.
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In your case if outer cylinder coil's voltage drop will be significantly lower (which means that the voltage during recharge will be higher!) than the other, your CDI is eligible for final stage transistors replacement.
If, as you've already pointed out, the coil in question is good and healthy then I'd have to agree with ventYl that the problem might be the CDI. I feel for you, because that's my old CDI you're running in the bike, right?
It does sound like the transistor that controls the cylinder 1 & 4 coil may be having trouble grounding the coil properly.
Of course, the actual dynamic of your ignition issue is probably a bit more complicated than just the slow demise of the CDI's Darlington Transistors (one for each of the two coils). The CDI may have been delivering a weaker-than-normal spark to cylinders 1 & 4 for some time which could result in carbon buildup on the spark plugs, making misfires even more probable.
I guess the capacitors and transistors in these old CDIs weren't intended to last forever. They do the "hard work" in the CDI - capacitors dealing with 12volt power and the transistors dealing with grounding the primary winding of the coil. Those activities produce heat as a byproduct which ages the component.
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Could someone tell me what capacitor should i use on this old CDI of mine? I know the diod for the D1 is the same as the D2, but the markings on the capacitor thas just above V1 is burnt. I know that getting this to work is a long shot, but i tought i would give it a try before i start to tear apart my currently working CDI.
(https://lh4.googleusercontent.com/xkjX9FjY_-8I5jSiHlIjydfQUnykxLTT88psSbpRDeVfdZ-GaLRdE5VOphlv9hAG_WcIMcFqCzsxuPxxxNk7z4J3LD7tYrftFjaO=w1886-h823)
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IIRC I've written it somewhere here on forum into different thread. Together with info that from what is available off-the-shelf, TIP150 switching transistor works as replacement of original switching transistors. (at least worked for me).
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Yes, i know that i can use the TIP150 for replacements, but what about the burnt component? Does anyone have any idea what it was?
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i can take a look at my repaired CDI at home and read out values from capacitors.
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That would be great!
Thanks in advance :)
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Oh no! Good luck with the repair, I hope that replacing the components sorts it out
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The two larger are 47uF / 50V electrolyte each.
The two smaller are 10uF / 63V electrolyte each.
Voltages are not mandatory as long as they will be above 12V. I got the ones which were available off the shelf as long as they were small enough to fit into box.
direction of negative lead can be seen in the picture
I took the time and swapped the unit into motorcycle if it runs and it is (the bike from which this ignitor originates is already dismantled for spares and the other uses Pietcard replacement). Unfortunately I cannot write the ignitor ID code because label is completely washed down (but the rest of bike looks like England-specced 1991 Bandit).
edit: I found out the image of your burned CDI just right now. The positions C30 and C7 are both free (unconnected) on my CDI. I did not trace the circuit but it is possible that C7 capacitor is part of RPM limiter on some newer Bandit CDIs (post-1992 Bandits should be limited to 170km/h).
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Okay, but whats that black thing? The thing that's just below C7?
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Dunno :S
PCB label is V1 and text printed on part says: [M] 7k270 s06.
Datasheets say it is varistor which nicely correlates with V1 label printed on PCB.
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This just sucks, so i think there is nothing to do with this CDI, i should have another broken one lying around somewhere, but i can't seem to find it. I guess there is nothing to do but to change the transistors and caps just in case. I checked the spark also, it was kinda purple and weakish. I had new spark plugs in and i found out that just after 40 km ride or so, one of the brand new spark plugs was miss fireing, or the spark was not between the electrodes. This bike is giving me a headache...
But i shall overcome this! :)
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Try to get above mentioned varistor (based on datasheet any part compatible with 7K270 should be OK). If there is no additional damage to some other part it might be working again (if it is somewhat working it is chance that rest of CDI is OK). But the question is what caused such a damage to PCB?
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The guy whom i got it from said that he was tightening the positive plug on the battery and accidentaly shorted it, after that the bike stopped and never ran again. When i pried it open, the varistor was complitly burned. Both D1 diode and this varistor burned.
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So go for the replacement. I think that with transistors and caps you can get to price not more than 20 Euros on parts. IFF CDI is giving you weak spark then varistor is probably not in some very important circuit (thermal compensation?) and there will be need to replace other pars (elyts) too to get it working nicely. Good news should be that while CDI gives you some signal none of really expensive / hard to order parts should be damaged (mainly CPU, xtal, memories).
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Just to be clear, the CDI i have on my running bike is from Greg. It works, but yeah, has all sorts of problems that i have listed here. The CDI that is shown on the picture is from ebay, i got it with one of the side covers for free, i thought that i should give it a try first, before i tear open the working one and start replacing parts.
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oh well.... now I get it. try to replace the varistor and elyts, they should be cheapo. Then try if it gives you at least some spark. If not and/or will burn again you know it is dead :)
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okay, a little update. Changed the caps, did not do a thing, maybe a little change, but hardly noticeable on idle. Had some trouble @ startup once, lost spark, disconnected the signal plug, and it fired back up.
All points to what Greg said about the transistors, it seems like a grounding issue. I had to order the TIP150 and hope it arrives in time so that i can change those as well, at least i know what to do when the bike does not want to start.
FIY, i have opened up about 4 different CDI-s as long as i have had my bandit and every single one looks completely different
Heres the picture of the one i opened.
(http://www.upload.ee/image/4788722/WP_20150619_001.jpg)
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Just a thought that occurred to me... Have you inspected the bike's main ground lately? The large Black wire that is bolted to the engine crankcase. Sometimes a main ground can get loose or corroded. Just a good idea to make sure all is okay at that end of the business
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This is getting irritating....
The no 3. cylinder keeps fouling spark plugs. This is the third spark plug in about 3-4 days...
All the other seem to work. The other thing i noticed is that when i accelerate it does not lag or sputter at any rpm, but when i keep it steady around 4-7 it starts to sputter, like one of the cylinders would be misfiring or runs lean.
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This is getting irritating....
The no 3. cylinder keeps fouling spark plugs. This is the third spark plug in about 3-4 days...
All the other seem to work. The other thing i noticed is that when i accelerate it does not lag or sputter at any rpm, but when i keep it steady around 4-7 it starts to sputter, like one of the cylinders would be misfiring or runs lean.
Btw, what makes you think this is an electrical problem?
The fiddling with the wires might just be a coincidence.
I've had quite some problems with running on 3 cylinders over the last 5 years, and they were always related to only two things:
- Runs on 3 only cylinders at idle --> pilot jets clogged
- Runs on 3 cylinders but comes alive (not always) at full throttle --> sparkplugs and/or the wires/caps have become wet/dirty. Might be caused by clogged spark plug drains and/or worn rubbers. It's possible that running on 3 cylinders fouls the plugs making it worse.
I was always able to fix the problem by cleaning the plugs with a steel brush and cleaning the spark plug hole.
Another possible cause might be one of your carbs having a problem with the needle causing too much fuel at constant throttle.
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Just a thought that occurred to me... Have you inspected the bike's main ground lately? The large Black wire that is bolted to the engine crankcase. Sometimes a main ground can get loose or corroded. Just a good idea to make sure all is okay at that end of the business
Sorry for this hijack question.
Is this the black wire that you are talking about?
The starter motor is also grounded to it. It's basically under the cam chain tensioner.
https://dl.dropboxusercontent.com/u/22072961/MF/2015-06-24%2016.17.56.jpg
I'm having some ground problems myself, losing almost 1V somewhere on the ground.
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Yes, that's the B4's main ground, on the aft starter mounting point.
I've seen main ground problems on other motorcycles, mainly Kawasaki. The main ground on my 2005 EX250 was badly corroded when I bought it (the bike was only 4 years old at the time!). There was corrosion (white-ish, fuzzy-looking stuff) down inside the aluminum threads cut into the engine block. Cleaned it out, put some dielectric grease along the threads and things have been good ever since (9 years of ownership).
Also, it's important to trace back along that main ground to its connection at the battery.
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Yes, that's the B4's main ground, on the aft starter mounting point.
I've seen main ground problems on other motorcycles, mainly Kawasaki. The main ground on my 2005 EX250 was badly corroded when I bought it (the bike was only 4 years old at the time!). There was corrosion (white-ish, fuzzy-looking stuff) down inside the aluminum threads cut into the engine block. Cleaned it out, put some dielectric grease along the threads and things have been good ever since (9 years of ownership).
Also, it's important to trace back along that main ground to its connection at the battery.
Where else is the wiring harnass grounded to the frame?
I've disconnected that main ground wire from the picture (indeed goes from battery ground terminal to crankcase) but I'm still measuring continuity from the frame to ground wires from the wiring harnass. Battery is removed as well.
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Where else is the wiring harnass grounded to the frame?
I've disconnected that main ground wire from the picture (indeed goes from battery ground terminal to crankcase) but I'm still measuring continuity from the frame to ground wires from the wiring harnass. Battery is removed as well.
First: From the Suzuki factory there's nothing, I mean absolutely nothing grounded directly into the Bandit 400's frame.
There are a total of 4 (four) grounds on the B4's and all of them are engine crankcase grounds: 1. the main ground line from the battery, 2. the ground for the starter motor, 3. the Oil Temperature sensor is an old-school, one-wire "through body" thermistor-type of sensor, so as it heats up it grounds into the metal of the engine, 4. the Neutral Light sensor is also a "through body" sensor, it grounds into the engine when the "neutral bump" on the transmission shift-drum depresses its button.
That's it, a total of 4 grounds. You can look at the electrical wiring drawing in the Bandit 400 and see there are only 4.
For the purpose of your measurements, though, if there's anything grounded into the engine crankcase it might as well be grounded to the frame because there's a very good pathway through the engine mounts into the frame.
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So, i found the problem. You can watch it in this video
https://www.youtube.com/watch?v=Uao_G5f-_Ns&feature=youtu.be
i have to change the spark plugs aswell, but at least i got all the cylinders firing correctly.
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Reply for your question asked in video is: yes the plastic part does come out as well. The are held mostly by dirt and emulsion tube tension. Underneath, there "secret O-ring lives".
The best way to get it out is to push the finger from inlet. After some time it will go out (and your finger will hurt a bit).
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I'm surprised it ran at all!
To remove the slide holder you must remove the slide and the float holder then unwind the main jet one turn and push it inwards with your thumb, the emulsion tube will move upwards,
Continue unwinding the main jet and pushing it inward until the emulsion tube is lose.
Sometimes the slide holder pops out but usually only the emulsion tube.
After this you can put your fingers into the front of the carb and push the slide holder up and out, not easy!
When rebuilding remember the emulsion tube only goes one way around due to a cut-out.
Be careful not to damage the slide holder when refitting due to over tightening the main jet.
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it had terrible starting problems yesterday and the no 1 cylinder only fired at around 6+ rpm, it was that lean, that also explaned the sucking sound.
But, i still wonder why these manifolds broke. these were pretty decent, when i got them from ebay, i only replaced the stock clamps. I think that overtightening the clamps broke them, so i used the original ones, im going to see how long they are going to last.
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my bandit stopped running on all four last sunday but i still had no time to see what is wrong. i only checked the spark plug if it is not cracked. maybe i overtightened them too :/ i have to check it.
btw I am missing the crucial point in my latter post: you have to get the main jet out before trying to get the slider holder out.
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Glad to see that you've discovered what's wrong with your Bandit.
It's funny, that's the exact same failure that used to happen on the SPICA Fuel Injection equipped Alfa Romeo cars. Leaks would develop in the hard rubber connectors between the fuel injection manifold and the cylinder head, which caused the engine to run really poorly (due to lean mixture).
People used to get angry and pull all the SPICA fuel injection equipment off the car and install Weber carbs. And because the Weber carbs use a different connector to the cylinder head the original cause of the problem would get fixed quite by accident.
Congratulations on figuring out your problem. Now you can get the bike back in shape.
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today; finally i had some time to look why bandit runs on three cyls. not a catastrophic scenario, "just a dirt" in pilot jet.