not firing on 2 and 3- options?

[jstone8952]

bike is a 1980 gs550l

so this thing has been a pain in the ass so far. just had the carbs torn apart dipped cleaned and rebuilt. put em on and the thing is hell to start and when it does it only fires on 2 and 3. im assuming its the coil but i am not positive how to check. ive got a multimeter but im not too sure how to read it lol.

i cut open the wiring harness to see whats going on in there and theres a million wires in there. the bike also has tons of wires that have open ended connectors going to nowhere. i have the wiring diagram for my bike but i am kind of scared to mess with everything.

i was thinking though... i mean how hard would it be to just rip out everything, i mean EVERYTHING and just solder up a new harness?

i mean there is the 3 wires coming from the starter to the rectifier thing. theres the ignitor- thats what powers the coils. why not just hack out all the old **** and run my lighting on a switch? there shouldnt be as many wires in this thing as there are and i feel like there just may be a gremlin in all of the connectors and spliced wires.

i just want minimal wiring. i want the bike as simple as possible.

[Mith]

Have you checked to see if you are getting spark on the 2 and 3 plugs? If so I would start with a valve adjustment just because it needs to be done and could make it hard to start. Did you bench sync the carbs?

[mike_of_bbg]

Your title says it's not running on 2 and 3 then your text says it's only running on 2 and 3? Take an extra spark plug or two and plug the wires into them, then lay them on the head for grounding. Turn the lights off, crank the motor and see if you get fat, juicy, blue spark out of them.

To check your coil secondaries, pull the plug boots off the plugs 2 and 3 (or 1 and 4) and measure between them with an ohmeter. Should be around 25k ohms. If it's very high, try unscrewing the plug caps (they just screw in to the stock wires) and measure those from end-end. They should be about 5k each; but are known to go bad after a while and go very high or even completely open. If you remove both boots you can measure from copper core -> copper core of the wires, which should be around 14k ohms.

The primary connections are found under the tank. Just unplug from the harness and measure between the leads; they should be about 3 ohms.

At least the coils are easy to test.

[jstone8952]

sorry its only running on 1 and 4. 2 and 3 are not firing.

the bike ran with the wiring the way it is so im scared to gut it but im finding it difficult to trace wires with so many of them.

2 and 3 have no spark. what setting should i put the multimeter on to test the resistance between them?

I also was wondering- when i got it started the rpms were really high at idle so i was playing with the knob at the base that affects the idle. im not sure where it needs to be? is there any information on this? even my mechanic was just guessing when he adjusted it...

[jstone8952]

and not sure if it means anything but with the multimeter on 20v i measured the wired leading up to the coils and they read between 10 and 12 all the way up to both coils. is this significant?

[mike_of_bbg]

First, I wouldn't think about ripping the wiring harness apart yet. If the bike was running before it probably should again. If you're not firing on 2/3, you need to find out why. Your engine runs a "wasted spark" system: cylinders 2 and 3 fire at the exact same time, once nearing TDC compression and once nearing TDC exhaust (this simplified the mechanics and lets them run the ignition right off the crank). So the ignition of those two is intrinsically tied together. BUT you also just rebuilt the carbs (or had them rebuilt?) and that's a change.

Mith asked if you bench sync'd the carbs - did you? Could it be that the throttles on 2 and 3 are simply too closed at idle? Will the motor rev at all if you slowly open the throttle? Did you actually test for spark by laying the plugs on the head? Or are you surmising that they're not firing because the pipes are cold? If they were not open enough then they should get warm if you open up the throttle enough.

To test the secondaries you want to set your multi-tester to its highest ohm-meter reading, which is probably 200k ohms. The primary impedance is MUCH lower, and you'll want to set your ohm-meter to its lowest setting, probably 200 ohms. Components should never be powered, and should be isolated, for resistance checking. That means pull the harness plugs on the coils before checking the primaries. That you're getting 10 to 12V is a good sign that the coils are at least getting power. Boots are very easy to change. If either coil is suspect they're also relatively easy to check by trading places (secondary and primary of course).

[Sandy]

Do this without actually trying to start the bike, just crank it over with the plugs out and grounded. Move the trigger wire, not the orange wire, from the 1 - 4 coils to the 2 - 3 coils and see if you now have spark on 2 - 3. If you don't they're either not getting power (the orange wire) or the coils are toast. If they didn't fire now move the orange wire from the 1 - 4 coils to the 2 - 3 coils and if they still don't fire it is definitely your coils. If they do have spark after you moved the first wire then your problem is in the trigger circuit for the 2 - 3 coils. Trace that wire back to see if it's broken, grounded somewhere or disconnected, it's possible it got broken or disconnected while doing the carbs or you have a bad igniter or trigger.

[jstone8952]

i had the same mechanic work on my past 3 bikes that had carb issues. for 300 he comes out to me takes them off takes them to his shop and dips them disassembles them and rebuilds them with the kits i get. my problem in the past has been that i tend to overestimate my abilities and spend 6 mo trying to figure out what ive messed trying to "fix" something. sad but true.

i will test to see if im getting spark as soon as i get home. as far as having the carbs bench tested? what does that mean and would a good mechanic (all 3 of my other bikes started up as soon as we got them back together) have done this?

[jstone8952]

also if the coils (meaning the orange wire) are getting 12v does that rule oput the ignitor as a possible suspect?

[Sandy]

also if the coils (meaning the orange wire) are getting 12v does that rule oput the ignitor as a possible suspect?

No, the orange wires only provide 12V to the coils with the key on. The other wire is what actually triggers the coils.

[mike_of_bbg]

Many here would admonish you for:

1) not working on the bike yourself, and
2) paying someone else to work on it

Unless you have a peculiar love for certain old bikes, the amount of work required and the consequent amounts of money to be paid usually makes it a losing proposition. Add to that, most mechanics don't really do a great job on older bikes (the few that will word on them). I have a local guy who does love the old bikes, does thorough and good work, and charges pretty fair labor: but I'd be going even broker even quicker if I paid him to work on my bike.

The point of sync-ing carbs is to get their butterfly throttle valves opening at roughly the same rates. There are some variables so occasional adjustments are required. A "bench sync" is a first-run try with dry carbs. Put them on the bench in a dark room, get a lamp, and adjust to get the same streak of light through each carb. Then at least they'll be close to in sync.

BTW, you should probably update your location using the User CP link in the upper left-hand area of the screen. Maybe someone is near to you that could offer you a hand. Also add a sig that contains your bike. You put that in your first post so we know in this case, but for the future...

[jstone8952]

from what ive read these bikes are relatively simple. not like my zx6, vf750 or vstar that had many parts that i couldnt begin to understand. ill be up dating my sig and loc as i had it all there previously but at some point the forum changed and i lost my username.

so the action plan would be to
1) take plug wire one and stick it on 2, then 4 to 3 and see if it makes a difference.
2) to remove plug wires 2 and 4 and stick a spark plug in them and see if i get a spark when theyre grounded to the engine casing
3) check resistance between 2 and 3 (assuming i stick a lead in each and set my multimeter to 200kohms?)

[mike_of_bbg]

No, the orange wires only provide 12V to the coils with the key on. The other wire is what actually triggers the coils.

When the magnet on the ignition rotor passes the pickup of the sig gen, it creates a pulse of electricity which signals the ignitor to momentarily pull the ground from the coils (the coils always have +12V). The pulled ground causes a collapse of the field created by the coil primary, which induces the high-voltage charge in the secondary, which becomes your spark.

Verify spark (or lack thereof) first. If there's no spark we'll see if the coil is to blame. It's not unusual for ignitors to go bad at this age. If we get down to suspecting that I have an old one that still works for a little while at a time which you can try (provided you're in the U.S. and I can get it to you at reasonable cost).

[jstone8952]

the ground being the b/y and white wires, yes?

[mike_of_bbg]

from what ive read these bikes are relatively simple. not like my zx6, vf750 or vstar that had many parts that i couldnt begin to understand. ill be up dating my sig and loc as i had it all there previously but at some point the forum changed and i lost my username.

so the action plan would be to
1) take plug wire one and stick it on 2, then 4 to 3 and see if it makes a difference.
2) to remove plug wires 2 and 4 and stick a spark plug in them and see if i get a spark when theyre grounded to the engine casing
3) check resistance between 2 and 3 (assuming i stick a lead in each and set my multimeter to 200kohms?)

1) you must also swap the coil primary connectors for this to work (basically you'd make your 1&4 coil your 2&3 coil and vice-versa). If 2&3 start firing then you probably have a bad coil or wirign.
2) yes
3) yes

I'd probably do 2 & 3 first, then 1 if there weren't any obvious issues with the coils.