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Fuel starvation or ignition? Surging but not dying

Buffalo Bill

Buffalo Bill

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82-GS1100G, all stock intake and exhaust.
Bummer, after 8 years/15,000 miles of perfect tune it's got a problem.
After riding a half hour it started to act like a fuel starvation surge and stumble.
Moving petcock to prime, does not change it.
Idles just fine, no stalling.
Opened up the carbs and I cant find a trace of deposit or buildup in the main jet system.
The riding time before it starts to happen is getting shorter, today I only rode a couple miles before it started again.
Is this an ignition problem?
Maybe sourced to the wiring harness and connectors in the headlight? I did handle those during my fairing project.
Thanks.
 
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If the vent hole in the gas cap is plugged, it would act as you described. Easy to check, and free, just saying, Tom
 
Venting perhaps... could also be the voltage wire to the coils has an iffy connectiono somewhere on its path.
 
Right geol; “could also be the voltage wire to the coils has an iffy connectiono somewhere on its path.”
I'll check the wiring path.
I'm thinking it needs an ignition tune up.
Reminds me of an old car I had, Corvair Van with the same symptoms. Needed new points and condensers, spark plugs and timing, ran great after that.
No points or condensers in my bike, that leaves spark plugs, wires and the ignition module.
Spark plugs are due for replacement.
 
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You should check the fuel venting first as it's the easiest to do - when the problem starts, simply pop the fuel cap and see if it disappears.
 
hillsy said:
You should check the fuel venting first as it's the easiest to do - when the problem starts, simply pop the fuel cap and see if it disappears.
Click to expand...
Seems the most unlikely thing, but I will check that too.
 
Stator gone bad?

Stator gone bad?

Ok, I'm mostly done with a total carb overhaul, dipped and reassembled, but am waiting for a set of O rings from Bob Barr.

Realized yesterday the stator is not working. I just replaced the cover gasket, but I don't see how I could have broken a wire doing that. I installed that Rick's Motorsport stator 9690 miles ago, but it looked fried when I changed the gasket. I should have done a voltage test before I used that gasket.
Explains the power fade if the bike is running on battery only.
 
Well 0.00 ohm reading between the leads, that's definite.
The bikes been running good for so long, I forgot how to recognize stator issues, or testing.
 
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Well WTF???
I bought a new Electrosport stator and tested the resistance between the leads before I installed it and got 0.00 ohms.
I figured it must be dead and returned it.
Then I contacted their “Ask an expert” email and got this response:

Hello,

0 ohms is not the same as no connection. The resistance should be as low as possible, typically about 0.4 ohms. I cannot explain how your meter would measure 0.00 ohms on a good or a bad stator, that seems like a testing error.


Kyle Wood - Sales Manager
-------------------------------------
Procom Engineering / ElectroSport

21 Brookline, Aliso Viejo, CA 92656
PH: (949) 305-4200
www.electrosport.com
 
Have not yet found the problem!!!

Have not yet found the problem!!!

Bike runs fine and normal until I do a couple hard accelerations up to 7000RPM, then it goes bad, and won't rev past 3500, and surges; bad-good-bad.
Returns to good after overnight cool down.
Wow, seems I'm going through the all engine systems, updating all maintenance looking for this issue and still have not fixed it. :confused:

Carbs cleaned with O rings replaced,
Airbox detailed,
Stator and R/R replaced (tested bad),
Timing sensor and igniter tested good.
Plugs replaced,
Caps and wires detailed, (spark looks very good)
All wire contentions checked or updated.

Next check will be tappet clearance and timing chain.
 
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Maybe do some testing...
Does the problem happen on "Prime" (maybe a vacuum diaphragm/valve problem)? Does it make any difference if its on "Reserve" or "On" (maybe dirt in the filter up in the tank). Have you unhooked the fuel line and just let it run into a can to see if the flow slows down (another sign of dirt in the filter- or a plugged vent)?
Im just offering up some no cost checks...
 
TxGSrider said:
Maybe do some testing...
Does the problem happen on "Prime" (maybe a vacuum diaphragm/valve problem)? Does it make any difference if its on "Reserve" or "On" (maybe dirt in the filter up in the tank). Have you unhooked the fuel line and just let it run into a can to see if the flow slows down (another sign of dirt in the filter- or a plugged vent)?
Im just offering up some no cost checks...
Click to expand...
Thanks, but those were the first tests I did.
 
I'd suspect the ignitor is failing when it gets toasty- hard to check unless you carry spare spark plug (and wrench, glove). Next time it happens , use your spare spark plug in plug wire to #1 to check spark: then switch to check either #2 or #3 circuit for spark- you might find that one half of ignitor is unhappy.
 
tom203 said:
I'd suspect the ignitor is failing when it gets toasty- hard to check unless you carry spare spark plug (and wrench, glove). Next time it happens , use your spare spark plug in plug wire to #1 to check spark: then switch to check either #2 or #3 circuit for spark- you might find that one half of ignitor is unhappy.
Click to expand...

Thanks, I just did that test today after the symptom appeared, ample spark on both 1-4 and 2-3.
I was suspecting that too, and discovered some spark leak from the resister cap and wire connections, and fixed it. Did not have any affect on the symptom.
 
Since you mention an "ignitor" I am assuming it has CV carbs. See the sticky at the top of the carb section on CV TUNING PROCEDURES. My guess is some float level tweeking will cure the ills. Its the first thing I would check anyway. Too low and they drag at the lower RPMs like near 3,000 or so. Too High and they tend to hit so rich the cylinders cant burn it all and it gets a jerky feeling to it. Start it and have a buddy run it up around 5 and stand behind it ..bet it smells gassy as heck.
 
I took a ride and because the issue is predictable, I can manage it. If I do not do any hard accelerations, it will run normally.
I'll buy a used CDI from ebay, seems I've been working around issue.
It feels like the ignition is not advancing the spark, or cutting out 2 cylinders.
One last thing, I'll clean the CDI connectors.
 
Have you pulled the timing plate and cleaned the governor and the crank end to be sure there isnt any sticking going on down there?????
 
Yes Chuck, tested the sensor too. All good.
It has electronic ignition, not points.
I bought a used CDI box today, last thing to try.
It acts just like an old car I had, new points and condenser fixed it.
 
Im late to this thread but will add things that happened to me with similar issues:
As I absolutely know you know what you are talking about so i reckon this is a simple thing you will have
overlooked.


- Is it fuel line kinking ? This for me produced the same issues as you are experiencing !
- Is it petrol vacuum line kinking to carbs ?
- The connection from the pickups to the coils (usually a plastic connector box) might be loose.
On one of my bikes again it produced exactly the same issue you are experiencing.
simply wiggling this when the hesitation started made it go away.
A new box and connectors solved the issue.
 
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