Bonneville America Forums Forums Technical Forums General Tech Opinions please on intermittent spark issue.

Following on this thread (link below), where Mag10 suggested a voltage issue, I did the R/R mod and have some initial observations.

http://www.bonnevilleamerica.com/forums/...true#Post623530

Before specifically using my meter on the stator and R/R, I thought I'd see what people think may be going on with my bike. I was looking for advice in the procom thread because I replaced my CDI with procom, but only saw some improvement - like others, my bike is now too cold blooded for my liking with the procom. Mag10 suggests that it is a low voltage issue. After the R/R mod, I see some improvement in output, but wonder if the R/R itself is bad, possibly the Stator, or quite possibly my battery is not dead, but should be replaced?
Here are some numbers, all readings in VDC off the battery terminals:

Battery, ignition off: 12.6
Battery, ignition switch on: 12.1
During crank: 11.6
After start, rough idle: 12.5
Using a spark indicator, both sides are intermittent.

Using the choke, the idle is very 'finicky', and I have to slowly adjust it to somewhere around mid-choke to get a smooth idle. It will not take throttle while the choke is engaged. If you care, you can see in this thread where my problems first began. The bike USED to start and idle beautifully on full choke and I could ride it (give it throttle) right off.
http://www.bonnevilleamerica.com/forums/...part=1&vc=1

Back to voltage readings:
After 20 seconds or so, I can put the choke in. Here is what is most important, I think:
At idle speed 1100 RPM (normal), I get intermittent spark and around 12.5 VDC. If I turn up the idle RPM to 1300, I get smooth running, good spark and about 14.1 VDC. If I leave the idle speed knob 'as is' and shut her off, the next cold start shows improvement:
Resting battery: 12.6
Idle at 1700: 14.8 V; good spark
Dial RPM down to 1300: 14.1 V; good spark.
Dial lower to 1100; intermittent spark and 12.5 vdc.

I have left the idle RPM set a few hundred high and am riding that way for now. So, it seems a bit 'chicken and egg' to me. Not enough output voltage = poor running, but increasing RPM puts out more voltage = better running.

Thoughts?? Thanks!

Just found this thread on an alternate choice for CDI. If my problem doesn't turn out to be something else electrical, I may look into this.

http://www.bonnevilleamerica.com/forums/...ge=0#Post624656

Bump. I may get some time to work on the bike this weekend, so thought I'd see if anyone has anything to offer on the subject. Thanks.

What is the voltage across the battery terminals at NORMAL idle and at 3000 RPM?

Short answer: Warmed up, idle at 1100, V=12.3. throttle up to 3K, V= 14.3.

Long answer: At start, RPM is "jumpy" and varies from 1100 to 1200 or so, while voltage fluctuates from 13 to 14 and does not respond to throttle until engine has warmed up. If I adjust the idle RPM to 1300, V= 15 and at 3K, V=14.3 to 14.5, but it is hard to hold RPM steady, it goes up and down by about 500, but the voltage does hold around 14.3-14.5 at RPM anywhere from 2K to 4K.

After warmed up, it is easier to hold RPM steady at 3K (V=14.3), but I seem to hear occasional misfires / backfiring.

If I dial the idle RPM back down to 1200, V= +/- 13 V but the idle fluctuates and the neutral light has a slight flicker to it. If I dial RPM up to 1300 RPM, Voltage goes to 13.5 and the neutral light stops flickering.

Basically, my bike does not like RPM below 1300 and /or voltage below 13.5 V and is (IMO) very cold blooded at start, even though it is 80 F ambient. One change from before all this began is it now starts with the choke, but runs poorly unless I put choke in 1/2 way immediately, and then after maybe 10 or 20 seconds push it all the way in. But then it won't respond to throttle until it warms up after a minute or so. And I have to dial up the idle RPM to 1300 or it idles like crap.

Presuming the plugs are in good shape & they get healthy spark when grounded to the cylinder/head then my bet is on the R/R.

You might also want to test the coils per the Haynes manual.

The ignition sensor a/k/a pick-up coil is another possibility, however they don't normally fail in the manner of your bike's symptoms.

If you can at least temporarily try a known good R/R then you can rule it out...if you buy one and that is not the problem then it can be sold pretty easily, as the OEM R/R is a common failure/weak point, at least on the carb bikes.

Hook up a battery charger to the bike and get the voltage to over 14 volts. With the charger on, start the bike to see if the idle improves. If the Procom is voltage sensitive, this should confirm it since the voltage won't drop with a lower idle.

Mike, to maintain continuity try and stick to one post. It helps with the bigger picture.

In the first link above you stated that the dealership upjetted your bike? Why? If it ran good before, upjetting to address a symptom could cause future problems. You stated that the bike started fine with the choke on originally but you always needed the choke even after a short stop. I agree it sounds like your bike was lean but it wasn't a problem for you. Having said that, when properly jetted, these bikes only need the choke for the initial start (depending on temp).

For me (after the initial start/choke sequence) any start, even a couple of hours after the original, wouldn't need it. Also, you should have good drive ability with the choke on, other than a slightly higher idle. How big did they go with the jets? What is the config of your bike (exhaust, intake)? Your bike may be so rich now, that you don't need the enrichener any more and you also have the Procom variable?

If it is that rich you should be concerned about washing out the rings and/ or oil contamination.

Good idea with the charger; I only have a trickle charger, but could maybe borrow one. That said, I finally got around to checking some readings. Stator output was fine. R/R diode check indicated failure. It does not appear that my failed R/R is affecting the charging system by either overcharging or under (not) charging the battery. I guess it's possible that it is simply not putting out enough voltage at low RPM. My battery also indicated a voltage drop on a bench load test, so first I will replace the R/R, then if not 100% corrected, will replace the battery. It is aging and was discharged several times during diagnosis, so would not hurt to replace it anyway.
Jetting - The dealership thought they had found the problem when they replaced the CDI, but when they found that it still idled rough, they figured mixture issue, so pulled carbs, cleaned some carbon on one side (from misfires?) and upped jets from 120 to 122.5 (or possibly 125, I can't remember right now) and 40 to 42. My bike is stock except for I removed the AI. When I told them that, they said I should have upjetted, which is one reason why they did it. I didn't think that was necessary, but I do believe my bike was lean before. With ignition issues getting in the way, I don't know if she's rich now or not. Plugs have looked ok, but I haven't done a lot of riding because I don't want to run her till I know things are as they should be. Before all this happened, this was supposed to be the season I was going to try removing 1 baffle, going with a K&N and jetting accordingly. With any luck I can move on to that after replacing the R/R.

Thanks for all help! Mike

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Mike, to maintain continuity try and stick to one post. It helps with the bigger picture.

In the first link above you stated that the dealership upjetted your bike? Why? If it ran good before, upjetting to address a symptom could cause future problems. You stated that the bike started fine with the choke on originally but you always needed the choke even after a short stop. I agree it sounds like your bike was lean but it wasn't a problem for you. Having said that, when properly jetted, these bikes only need the choke for the initial start (depending on temp).

For me (after the initial start/choke sequence) any start, even a couple of hours after the original, wouldn't need it. Also, you should have good drive ability with the choke on, other than a slightly higher idle. How big did they go with the jets? What is the config of your bike (exhaust, intake)? Your bike may be so rich now, that you don't need the enrichener any more and you also have the Procom variable?

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I don't think your bike is set too rich with those jets in place. Those jets would be fine for a stock setup with TORs only in place.

If you don't have a battery charger, unplug the headlight and use the trickle charger. Note the voltage at 1000 rpms and running condition. Sure does sound like the Procom units are voltage sensitive.