Ignition Troubleshooting

[Vested]

Hello! Glad to finally be a part of the board after going here so many times for various bits of info about the bike and possible mods.

Before the winter set in I bought a running GSF 400 from (August or September) 1992 and brought it to my apartment, where I disassembled it and moved it piece by piece into my house for a thorough cleaning and inspection. I've reassembled the Bandit after a long winter and nearly everything is working (sans "braking" light and the tachometer lights).

Now though it refuses to produce a spark. The coils (switched to stick coils, wired in series) read the correct primary and secondary resistances, as does the signal generator. 12V is getting to the CDI as well as both of the coils. Still though, while the engine freely cranks with a fully charged battery I can't get a single spark.

What are the steps to be taken to determine the cause of this issue?

Thanks for any help you can offer!

[stormi]

Hi Vested,

I don't know if I have an answer for you, I'd just say that I would want to change one thing at a time.  It looks like you changed a lot at once, then it didn't work.  Is it possible to say go back to the original coils and see what happens, then try another component, etc?  Take it from its last known working configuration and work towards the end goal? 

Other than that, I really popped up to say  to the Alley.

[r_outsider]

Hi there
Have you D/Led the service manual yet? It's probably the best place to start with electrical troubleshooting. Reading from section 8-6, it says under "No spark or poor spark" to check for defective plugs, coils, and signal generator/ignitor unit. Since I presume your plugs are new, as well as the coils, and everything is getting power except the plugs themselves, I'd guess, with my admittedly feeble and diminished knowledge, that the problem lies between the signal generator and the CDI. Maybe it's just a wire or a plug, maybe not.
Of course, I have bounced off my skull a few too many times, so maybe just get the manual!

[Vested]

Thanks for the warm welcome!

I haven't tried switching one of the old coils on yet actually. Just waiting for a warm day and some time to give it a shot. As for switching components, really the only swapped components in the ignition are the battery and the coils. Everything else is as I received it.

[canyonbreeze]

If you have access to an oscilloscope you can check if there are pulses being supplied to the coils from the igniter.

[Vested]

Trying to borrow a friend's quite old oscilloscope soon, hopefully that turns up. However, as a short term test tonight could I just jumper a LED between ground and the signal generator lead to see if that's the problem? I'd think it should blink as the generator gets some current going in the circuit, proving weather it's faulty.

(as an aside, I did check the resistance of the signal generator and found it to be in the correct range per the manual. does this not always relate to a good generator?)

[Vested]

Stormi wins! I misunderstood the coil wiring and had both coil sets wired backwards, with + to - and vice versa. While trying out the old coil packs I noticed they gave spark, at which point I switched the spade connections in the new stick coils and they gave spark too! Duh.

Now I just need to get the fueling down and all will be well!

[stormi]

Stormi wins! I misunderstood the coil wiring and had both coil sets wired backwards, with + to - and vice versa. While trying out the old coil packs I noticed they gave spark, at which point I switched the spade connections in the new stick coils and they gave spark too! Duh.

Now I just need to get the fueling down and all will be well!

Yay!! go girl power!! 

I'm glad you got it figured!!   Did you download the service manual?  The wiring diagram should help you out with the brake and tach lights, etc if you don't have those sorted yet.

What's wrong with the fueling?  Maybe I can go for 2 out of 2. 

[Vested]

Haha! Glad that made you so...well...glad! Well deserved!

I've been using the service manual all along, though it seems a mite tricky. Some of the wires aren't matching up exactly, and I can't for the life of me figure out where the oil pressure sensor hooks up to the wiring harness...

As for fueling, I do need to make sure I'm getting spark to all four cylinders first, but as of this moment it's coughing without picking up, even when I spray a bit of starter fluid into the intake. Before I put the bike back together I did mess with what I now know to be the idle control, so I'm thinking that might be an easy cause of this. I also drilled out the stopper plugs for the A/F screws and screwed them in all the way, backing them out 2.5 turns.

So, thoughts? Want to make my life super easy? 

[stormi]

I've been using the service manual all along, though it seems a mite tricky. Some of the wires aren't matching up exactly, and I can't for the life of me figure out where the oil pressure sensor hooks up to the wiring harness...

Damn,.. without access to a bandit anymore, I don't know if I can help with that anymore.  Perhaps someone else will chime in on that part.

As for fueling, I do need to make sure I'm getting spark to all four cylinders first, but as of this moment it's coughing without picking up, even when I spray a bit of starter fluid into the intake.

I'm pretty sure this still points to a spark problem.  The thing should be able to fire on the starter fluid regardless of your A/F mixture position...

Other than that, it could be that the motor is just having trouble getting started after the work you did to it... That's what happened when we did similar work to Dita a few years ago:
http://forums.banditalley.net/index.php?topic=5277.0

Before I put the bike back together I did mess with what I now know to be the idle control, so I'm thinking that might be an easy cause of this. I also drilled out the stopper plugs for the A/F screws and screwed them in all the way, backing them out 2.5 turns.

So, thoughts? Want to make my life super easy? 

I know that there are definitely posts in the 250/400 forum about the air mixture and stuff.  Depending on where you're located, I wouldn't be surprised if there's someone who'd posted "optimal" settings for your bike already.  Give a quick search, and see what's out there. 

Let me know if you can't find anything and I'll have another look around.
hint: great names to pay attention to when you're searching:
thief400, gsxr400racer, interfuse, pitterb4. There are others, but I didn't make a proper list before they called my name for the academy award,.. sorry about that, and sorry to anyone I left out.  It wasn't intentional.   

[banditv]

theres a fair chance that the a/f screw you talk about are just the idle mixture screws.
they are pre set at factory and shouldnt be touched.
when its "coughing" are you using no choke,part choke, full choke?
if it sounds like its more likely to start on no choke than full choke, its prob to rich and is wetting the plugs.
if its trying to start at full choke, you are prob to lean and cant light it up.
to richen it up, wind the screws out half turn at a time. i've always found 4 turns out to be a better starting point for just about any motor, car or bike.
had one motor that needed 7 turns out to idle properly.

[canyonbreeze]

The mixture screws have springs that keep tension on them.  This is to keep them from moving due to vibration.  The Mikuni tuning manual says that beyond 3 turns out the springs won't work.  A lot of people have 4 turns out so that's probably conservative.  If you needed 7 turns though you may consider changing the pilot jet.

[Vested]

Arg, so it's definitely a spark problem. I've been taking the plugs out and grounding them on the frame to check for spark. Every once in a while I'll turn it over and the plug will healthily arc away at a steady rhythm. I even got it to fire up after which it ran fine outside of a lean issue. But today it once again refuses to consistently spark/fire.

As for the a/f mix screws, given the mods I've done (filter, exhaust) I figured it was better to set them up in the base condition and be able to modify them on the fly as opposed to having to take the carbs off and drill the plugs out after the fact.

So, what are the thoughts? Given that it fired and ran healthily on all four, I'm assuming it isn't a coil issue as that should be isolated to one bank. The signal generator as well is reading a happy 100 ohms.

[stormi]

Hey Vested,

Any more progress on this? 

I would agree about the A/F mixture, set it to stock and work from there.  Just don't run it too long if it's really lean.

Couldn't be bad wires could it?  I think it's Interfuse or PitterB4 who's had more than his share of headaches with the wires themselves.  Original wires by now could be rather suspect.
If not that, I would still swap the original coils in and see if it runs right.  Otherwise, you're sort of down to Signal generator / CDI....

[Vested]

Progress yes!

I threw the original coils on to no effect, at which point I figured out hacking the cdi apart is probably the best answer. With a little soldering done I plugged in the box and tried starting it with a bit of starting fluid. Voila! Running bike. It wont start without the fluid though, and is slow to return to idle. The second I'll attribute to running lean thanks to the new exhaust and k&n, and the first maybe to the 7 month old gas? Thoughts?

Either way, thanks all and I'm sure I'll be around with more questions!