Bike runs great on side stand, sputters and dies when it leans right

[cp___32]

I have a few spare aftermarket drain plugs for the carbs from the rebuild kits so I am going to make a measurement tool and see how things change when I tilt the bike. I was hoping to read the plugs by doing a plug chop of sorts once the bike does but I am not sure how long it takes to see evidence of how the bike is running once it starts dying.

Im hesitant to go away from the notion it is fuel related since a poorly running engine could cause weak spark once it starts stumbling. The could were new from about 6 years ago and other than the last few weeks of firing it up to tune the carbs they and the plugs and caps have seen no running. I don't particularly like the NGK caps but might change those to something that seats a little more solid but they should do the trick since I am getting reasonable spark.
I'll try tilting the bike and probing around while it's off and then see if anything jumps out.

Nothing seems ems to flex enough to cause a leak on the boot side of things but I will check that again with some quick start to be sure. I might throw the carb tune on there again and see if anything jumps out. It would be good to identify once and for all what cylinder is giving me grief. I've never heard an old gs run so I don't know if mine sounds bad or not. Phone speakers and YouTube don't do it justice.

Ill do some more checks shortly and report back.
Thanks again for all the help (and encouragement)

[Brendan W]

Pulling a plug wire and it having no effect is a diagnostic test for a non firing coil. Assuming this is the case. Swap the ht leads from the coils to the other pair of cylinders i.e. swap 1&4 with 2&3. Now see what's what when you again pull spark plug caps. If the motor now stumbles on 1&4 you have found an ignition problem with one coil.
If that turns out to be the case the likely suspects are the coil supply plugs, and or the ignitor plugs.

[TxGSrider]

I kinda skimmed through this. If it were me I think I'd recreate the situation (and I didn't have a IF heat thermometer... which I do), then pull each plug and look to see if one or more looks different from the rest. If it is somehow a coil or if it is going rich on one cylinder, that plug should appear wet. If it is going lean (maybe a boot leak when the weight shifts or something, or a low fuel level) then one of the plugs may be whiter than the rest.
Now if I actually did it, I'd probably start by using my IF Thermometer and see if I had a cold cylinder and just pull that plug. Then Id concentrate on that cylinder, coil, plug, wire, carb, etc...

[dantodd]

Pulling a plug wire and it having no effect is a diagnostic test for a non firing coil. Assuming this is the case. Swap the ht leads from the coils to the other pair of cylinders i.e. swap 1&4 with 2&3. Now see what's what when you again pull spark plug caps. If the motor now stumbles on 1&4 you have found an ignition problem with one coil.
If that turns out to be the case the likely suspects are the coil supply plugs, and or the ignitor plugs.

does this work? I know you can switch 1 with 4 and 2 with 3 because it's a wasted spark system but wouldn't you be firing at the wrong time if you switched 2 for 1 or 4 and then 3 for the other?

[cp___32]

Because I didn't feel like pulling the carbs....again.... I checked spark. I found two issues. One is simple, but the other one not so much.

Used a spare plug to check spark on all 4 cylinders (just while cranking, there's no fuel in the bike currently). Propped the bike up on the bad side and checked spark. First I checked 3. Super strong spark. 4....one initial flash then nothing. I put the bike over on the side stand and checked again. Spark comes back. Put it in the middle. Weak, and intermittent. Back to the bad side and it goes away completely.
Swapped the feed cables for the coils and the problem moves to 3 and 4 works like a champ. Switched things back and checked voltage and resistance. 3.6L and 3.9R which seems good, but now for the one strange thing. Voltage was 11.59 on the right at the molex connector just ahead of the coil, only 10.2 on the left. I disconnect the left coil and the voltage jumps up to battery 11.59. Plug it back in and voltage drops. Checked continuity on the wires and found that I have an intermittent open on the O/W wire on the side that's malfunctioning.

Now, I get that I have to replace the wires to the coil. That's a no brainer. But I zip tied them to the frame and tried the tilt test again and still found that I lost spark when tilting right. There's no voltage or resistance change when I tilt so it must be something upstream. My next stop is going to be chasing those wires back to the signal generator. So Mike10....sounds like you're onto something. I'm pretty weary. Been working 50+ hour weeks and just came off back to back 12s so I'll give the brain a rest and dive into the side cover tomorrow.

You guys will have me up and running yet....

Thanks

[mike10]

I have seriously just about had it with this bike.
I took the carbs off and readjusted all the floats, put them back on and I have the same issue.
I am getting spark at all four cylinders. Checked and there is no spark leakage doing the spray bottle test. I was using a funnel with plenty of fuel to eliminate the petcock or a plugged tank. Carbs were just cleaned and rebuilt. Brand new gasoline.
There is nothing I can think of that changes between running on the side stand and leaning the opposite way except fuel flow but if the floats aren't to blame then what? I really can't keep throwing new parts at this thing. Besides most parts on the bike are new now and I am not going to just start replacing new parts with other new parts and hope I luck into a solution.

have you checked the spark while the bike is leaning to the right? to see if good spark is still getting to all four. As it is leaning left.

[cp___32]

Yes, when it's on the side stand all 4 plugs fire wonderfully. And when leaning either direction the voltage to the coils remains consistent (consistently lower on the left, so I'll fix the faulty wire). So My next stop is the signal generator. Not quite sure how I'll test it yet, but maybe I'll grab a test light and do the initial setup while on the side stand, and then confirm everything when it's tilted the opposite way. See if the light when it's at TDC goes out when it tilts.

[geol]

Brendan W told you the problem was with your ignition; probably coils and most likely wiring and not the coils themselves. Your different voltages the coil connectors is odd as voltage just comes down from the kill switch on one line and then just splits and heads into the two coil connectors. Since you have swapped the coil position and problem moved, wiring from coil connector to coil isn't the issue so look at the connector upstream from your points or igniter or whatever is there. I have found that Suzuki connectors can push out a pin when taken loose and reconnected and if you are not paying attention only a little bit of pin will touch the female part of the connector and you will have sporadic connection. I don't want to downlplay the miserable coil voltage especially on the one side and it needs fixed but I would take apart all the ignition connects and reconnect them working back towards the points cover and pay attention that none of the pins gets pushed out.

[Brendan W]

does this work? I know you can switch 1 with 4 and 2 with 3 because it's a wasted spark system but wouldn't you be firing at the wrong time if you switched 2 for 1 or 4 and then 3 for the other?

Not really that clever was it ?
Anyway just keep changing things until the problem moves.

[geol]

You don't have to move the coils if your spark plug leads are long enough. Just swap the wires coming from the ignition and of course, the bike won't run because the plug wires are on the wrong spark plugs but.... as I said, if the plug wires are long enough, swap those as well...

[cp___32]

More progress. I fixed the issue with the intermittently shorting O/W wire between the disconnect under the tank and the coil terminals. Found that the insulated spade connectors I had used originally were arcing so I swapped them out for tighter fitting non-insulated ones. Double checked the coil resistance (primary and secondary). I can't recall the exact figures but were something like 4.X ohm each between the spades and 17.X Kohm on the plug wires with the caps removed. Like I'd read, the coils are fairly robust so no surprise there. I fiddled A LOT with the ignition timing on the bike before I realized my spade connectors were suspect. I would get it so the test light would never turn off, then that it would never turn on....finally set it though, so the test light comes on at the full advance mark when the rotor is fully advanced.

I started my spark check once again while tilting the bike side to side, but ran out of battery juice in the middle of the test. All seemed well though so once I get back Sunday night or Monday night I hope to fire it up and see how she does with fuel.

One thing I did notice that struck me as a little odd was the coils were heating up while the ignition was on and the kill switch was set to run. They were both getting to about 150F at their peak. Anything I should be worried about there? I would have thought heating due to a poor connection with the spades but it was still heating up with the new ones on there as well.

[geol]

When coils are energized, they HEAT. They are cooled by air (if you can believe the position they are in under the tank) when the bike is moving. If the bike is sitting and they are energized and HEAT which you have observed. They can fail if the key is left in the on position indefinitely but there are other components that may fail first; generally the battery will just discharge before a lot of damage is done.

[Brendan W]

Ballpark, the coil will dissipate 35 W so that will heat it up some.

[BigD_83]

I once had the insulation wax (?) in a coil melt out when I inadvertently left the key in the ON position overnight. Left a nice white mess down the outside of the engine.

[cp___32]

I got back to it today. It seems that the contacts for the O/W and W wire on the Molex connector of the SSPB are loose and making intermittent contact. The problem has returned and I can't seem to find a happy place for the harness where it will work. I can put a spare plug into the plug cap and rest it on the engine and as I wiggle either wire in the Molex, I'll get a spark on the plug. The O/W wire in particular is heating up as it comes out of the Molex connector.

I've tried taking out the pins and bending the tabs further out hoping they wouldn't slide in and out anymore but that didn't work. Any advice on tightening up the fit between the male and female contacts so they don't slide in/out or move around? If tilting the bike while it's turned off is going to cause them to stop working, I have no doubt when the vibrations of a running engine are introduced it's going to get worse.