Stumble off idle Revised - Electrical help needed.

[wino59]

2002 Bonneville - Airbox, Off road mufflers, 42 pilot, NBZT needle, 1 shim, airhole drilled to 3mm, 120 mains.

Okay, so I posted awhile back about a stumble off idle, and thought it was carb related. As it turns out the carbs are sorted, the bikes runs great 95% of the time.

Here is what is happening, I found out that it really isn't a stumble, and more of the engine cutting out. It does not die, but runs on only one cylinder for a short time.

I can not duplicate it, it is random, however it generally does it at just off idle, or down shifting, and then when you go to accelerate it cuts out.

Not fuel related. The bike will run perfectly for 50 miles, then just decide to cut out periodically. The floats are not sticking, the carbs are sync'd, 100% positive not carbs.

In reading other posts, seams like it is either the coil or the air gap, but I am more inclined to think it is the coil.

Here is the question, given the fact that these bikes had known problems with the CDI, and the coil, should I just replace the whole lot and be done with it? Just to give me piece of mind, or just replace the coil and see if that fixes the problems. I know you can test the coil, but I have also had coils in the past that would test fine, but once heat was applied they would act totally different, so I don't put a lot faith in those tests as heat can play havoc on electronics.

Let me know if you think I am on the right track here, I have a 400 mile ride coming up this weekend, and I need to get it sorted.

Thanks

Chadd

 

[wino59]

Also to mention, I test the voltage at the battery, 12.5 sitting, when I reved it up it went in to the mid to high 13.50 to 13.9 volts, strange thing happened just off idle to 1/8 throttle, it would jump to 14+ volts and then come back down to the 13 volt range as I increased throttle, not sure if it is supposed to do that, I think it should gradually increase to maximum output, not jump from 12 to 14 then constant 13, but I don't know how the electrics are set up on this.

 

[Iceseven]

Chadd, the problems that I experienced with bad coils were when the bike warmed up then cut out, once it cooled down it started then failed again when warmed. Eventually the coil failed all the way but it happened gradually for my Scram.

 

[bluesforchallah]

Does it only happen when you're moving? Have you checked the cables to the battery to make sure they're good'n'tight?

Before you go throwing parts at it, if you know someone who you can try swapping parts with, this may help narrow down the possibilities.



I'm experiencing a similar issue. My issue is when the bike is cold. I'll start the bike and let it run for a few minutes. Once I push the choke lever in, and rev it up to about 2500-3000 RPMs it sounds like a misfire. This is with the bike stationary and not moving. Once the bike is fully warmed up, it doesn't seem to do it, but also doesn't seem to have the power that it should. I originally thought it was carb related as I was in the process of changing out jets and shims. However, now that I've got the carbs sorted out (with all new boots, clamps and vacuum caps) and back to original jet setting, the issue is still there. This also leads me to believe my issue is electrical. Last night after putting everything back together to test, I started the bike up and will going up thru the revs to test if the issue was still there, I noticed a small amount of smoke forming around the headlight bucket. Not sure if this was coming off the engine, the coil or in the headlight bucket. Again... leading me to believe my issue is electrical.

My issue:

http://s73.photobucket.com/albums/i...-85CA-E19C7FD82C87-11400-0000120BB06DCD7D.mp4

 

[Charro]

Also to mention, I test the voltage at the battery, 12.5 sitting, when I reved it up it went in to the mid to high 13.50 to 13.9 volts, strange thing happened just off idle to 1/8 throttle, it would jump to 14+ volts and then come back down to the 13 volt range as I increased throttle, not sure if it is supposed to do that, I think it should gradually increase to maximum output, not jump from 12 to 14 then constant 13, but I don't know how the electrics are set up on this.

Wino,
My voltage check on my 2001 Bonnie gave the same results. At idle it ran 14.3-14.5 volts, when reved up to 3000-4000 rpm's voltage dropped down to around 13.50. Like you I would have thought that the higher the rpms the higher the voltage. Is this normal for the Bonnie charging system, I don't know, maybe some one will chime in and clarify.

Andy

 

[Sal Paradise]

Strangely enough,when it was new my Bonny had a problem cutting out and someone told me to reroute the vent hoses under the sidecover. Fixed the problem instantly. In my case, the carb vent hoses were down under the motor just enough that in the wind they developed negative air pressure and lowered the fule level in the carb bowls. Caused a miss at 65 mph and then I couldn't reproduce it for days, then it would do it again.

 

[RumRunner]

Does it only happen when you're moving? Have you checked the cables to the battery to make sure they're good'n'tight?

Before you go throwing parts at it, if you know someone who you can try swapping parts with, this may help narrow down the possibilities.



I'm experiencing a similar issue. My issue is when the bike is cold. I'll start the bike and let it run for a few minutes. Once I push the choke lever in, and rev it up to about 2500-3000 RPMs it sounds like a misfire. This is with the bike stationary and not moving. Once the bike is fully warmed up, it doesn't seem to do it, but also doesn't seem to have the power that it should. I originally thought it was carb related as I was in the process of changing out jets and shims. However, now that I've got the carbs sorted out (with all new boots, clamps and vacuum caps) and back to original jet setting, the issue is still there. This also leads me to believe my issue is electrical. Last night after putting everything back together to test, I started the bike up and will going up thru the revs to test if the issue was still there, I noticed a small amount of smoke forming around the headlight bucket. Not sure if this was coming off the engine, the coil or in the headlight bucket. Again... leading me to believe my issue is electrical.

My issue:

Chris,

Does your bike run properly on start up and performance down the road once it's up to temp?

 

[bluesforchallah]

Doug,

The bike starts up fine. However, when it's stone cold with choke out, it doesn't idle above 1000RPM.

Once the engine get's hot to the touch, I shut the choke. The clicking noise you hear in the video happens usually after the choke is off and revs are up between 2500 and 3000 RPMs. Once the bike is really warm, the clicking noise more or less goes away, but the bike doesn't seem to have the power that it should. I've heard that when coils start to go bad, the symptoms can feel like a vacuum leak. And that's exactly what I've been trying to chase down. I've replaced everything between the carbs and the cylinder heads and the issue hasn't gone away.

I have Charlie in Texas sending me a spare Nology coil for me to try out. If I find that to be the issue, then I'll replace the coil. If not, then I'll start looking at the intake valves to make sure they're up to spec.

I don't think it's the ignitor as I had a spare to test with and found no difference when running the spare.

I posted this over on the 'other' forum:

So I went out into the garage tonight and started poking and probing around. Started with the Regulator / Rectifier, moved onto the coil and ended with testing the Pick-Up coil. Good news... I opened up the headlight bucket to test the R/R and found there was NO burned spaghetti.

Here are the results. Any thoughts or opinions would be appreciated.

Regulator / Rectifier:
Positive test lead on black wire with white stripe:

1) 9.19
2) 9.03
3) 9.85

Negative test lead on black with red stripe:

1) 12.20
2) 12.47
3) 14.56

Spark plug wires with probes in each end: 4.82 & 4.62 (my understanding is as long as they're both close in proximity, they should both be good)

Here are the results of testing the coil: Do the spark plug leads on the left seem low at 2.814K?

And finally I found the plug where the Pick-Up coil plugs into the wiring harness. With the positive test lead on the red wire and the negative test lead on the black wire, results were 0.613 (which is within spec). Until I get an extra gasket, I didn't feel like pulling the cover to test the gap of the PU. But if I'm going to crack it open, I might as well replace it.

 

[RumRunner]

Chris,

I'm not sure it will be interesting to see what happens when you get Charlie's spare coil. My bike with the FCR's will pop like that on warm up (no choke) when it's really cold out, but as soon as it get's up to temp she's perfect. Strange that your deal gets better with more temp, typically the electrical issues they get worse when they get hotter. I haven't done many electrical checks on my Thruxton so I'm not sure if your numbers or good, bad or average. The only issue I had was a charging issue that turn out to be a bad cell in my 18 month old battery. I keep telling myself that I'm going to do a bunch of electrical tests to have some baseline numbers but it's still nice riding weather. Maybe when I relocate my rectifier to behind the rear tire I'll do it.

Doug

 

[bluesforchallah]

:Fingers Crossed: