TOPIC:

Long story short, I rewired the entire bike. Headlight is LED with integrated signals, taillight also LED with integrated signals. Blade fuses instead of the old glass tubes. New 3 OHM mini coils and regulator/rectifier. Electronic speedo, Acewell MD52 is suddenly acting up. It was fine last year when I did the rewire, but I replaced the coils this year and suddenly the speedo freezes on me. It will read RPM and speed fine for a minute or two but then it just locks up . After warming up the bike I get a reading of 15 volts at the battery but I get a ?hiccup? where it will drop around 5 volts or jump to 19 volts. Because of the hiccup I replaced reg/rec but it didn't resolve the problem. This leave me with either the stator or speedo being the problem, in my mind, but I don't want to replace the wrong part, again, as I already spent $120 on a reg/rec that didn't resolve the issue. When the weather turned warm I checked the battery and the cells had run low. A new battery was part of my rewire so it is less than a year old. I topped off the cells. When it wouldn't start at the end of last season I figured the problem was the original coils still on the bike. Now it runs, at least in my mind, perfectly, except for the darn speedo. Well, it doesn't like to start in the cold either. I love the bike, but my wife would rather I buy a new one and quit spending money on this one. It's hard to explain why I would rather have this KZ, but I absolutely would love to resolve this issue and keep sinking money into new tires, exhaust, etc, on a classic rather than a bike off the showroom floor. Is this a stator issue, or just a trash speedo? Maybe my coils should be 5 ohms? I was an airframes mechanic in the military so I'm not to sharp on the electric, but damn if that bracket for the mini coils doesn't look good

Bike is a 1981 KZ650

When you say the voltage jumps around, are you looking at a voltage readout on the Acewell? I would not trust it for actual troubleshooting. A dedicated multi-meter would be more reliable source to see how the bike is charging. When you put the voltmeter on the battery, it should not jump around too much. It might swing from close to 13v to about 14.5v, but not jump, and never below 11.9v as long as the charging system is working. If the voltage jumps around from 5v to 19v, it could be the battery is defective. Even a bad reg/rec wouldn't cause that type of voltage behavior on a good battery. But again, this is when measured by a dedicated voltmeter on the battery.

You will want to figure that out, or at least confirm that it's ok, before anything else since a faulty charging system can ruin everything else.

Incidentally, bikes like the KZ should not really use the mini coils. Truly "mini" coils are designed for ignitions with a very controlled dwell system. Without precise dwell control, the mini coils can overheat and their life gets shortened. They will work , but they are just not physically big enough to dissipate the heat generated by long dwell (which happens on the Kz at idle or low RPMs) in the long run. Some "mini" coils are pretty big, so they can handle it, but some are pretty small, like the Dyna mini coils. This would get exacerbated by an overcharging issue where the battery voltage might be higher than normal, so be sure to get that charging voltage so that it doesn't really go above 14.5v, preferably 14.2v.

The Acewell actually shows a steady voltage. It's the multimeter that's showing the drop and spike. I'll take the battery and have it tested. I had the tender on it all winter and it's pretty new so I was surprised when the levels in the cells were low, but that could be the issue. Thanks.

Are you using a smart charger that can detect when the battery is fully charged, and then goes into a floating mode? Inexpensive chargers are merely on or off and can boil the water out of a fully charged battery if not disconnected.

Usually the cheapest battery chargers are "float" chargers. They let the battery voltage float to whatever is natural for the state of charge on the battery, rather than forcing a regulated voltage on the battery, which could boil it out.

A smart charger goes into a monitor mode where it is not actively charging, but is simply reading the voltage to see if the battery needs a top-off.

A smart charger is best, but a float charger of the appropriate size works well too as long as you remember to turn it off after 12 to 24 hours. A car float charger is sometimes too powerful for a motorcycle battery, so you have to remove power much sooner for safety, but then you might not be topping-off fully. I use a 2-amp car float-charger with a 1 or 2 ohm, 10 watt resistor in series to allow for a really slow, easy float. That way if I accidentally forget about it for a week, it will still be fine. But it takes a very long time to charge a battery that way, so I usually only use that in the winter. In summer I use the normal 2-amp float and just do whatever I can to remind me to turn of f the charger after a day.

With a float charger, when the battery is nearly charged, the amp draw greatly reduces because the battery voltage "floats" up, thus preventing excess current. With this design, as long as the charger is of the appropriate "size", there is a self-protecting mechanism at play.

I should specify that the above is for lead-acid, wet or AGM sealed batteries, not lithium.

Thanks for the corrections.

I didn't mean to correct, I should have said some smart chargers go into a monitor mode. Others might go into a float mode, like you said.

The instructions for the last cheap charger I owned (bunch of years ago) said to leave it connected until you could hear the electrolyte bubbling, then unplug the unit. I hope that the current crop of cheapies are better than that.

TexasKZ wrote: The instructions for the last cheap charger I owned (bunch of years ago) said to leave it connected until you could hear the electrolyte bubbling....

Yikes

Update: Ordered a new stator and got it installed. Still got the erratic readings on the multi-meter. Being an electronic meter I never considered it was picking up vibration interference until now. Picked it up off the bike and got a steady 14 volts.

Electronic speedo was still acting wonky. Start the bike and after a period of time, it just freezes, displays random numbers, etc. I came back in the house racking my brains when I realized I may have created my own problem. I pulled up my order from Z1 for my coils and plug wires and sure enough, copper core.

Try resister plug caps.
Steve

Like Steve mentioned, if you don't use suppression in the ignition system's high-tension circuit, it will make sensitive electronic devices act crazy. I've had meter do this.

You want to have suppression (aka resistor) wires, or plugs, or plug caps. You want at least one of those, but also not more than one.