The International CBX Owners Association

Is there a set behavior for the reading on the voltmeter for different riding situations or is each bike different. Also does the regulator go bad gradually or all at once? Both my 79 and 80 are charging OK but the readings at the meter are different. The 80 has a new Yuasa MF battery and reads a little below 12 at idle and doesn't move past 12 until I am 3 or 4 minutes down the road and it moves up to about 12.5. I get up to about 40 and it reads 14 and going down the highway at 60+ it reads 14.2. I will take my 79 out tomorrow and go through the same ride and see what it reads. I do know the 79 never gets to 14 no mater how high the rpm's.

So may variables twine, they can do all & none the same....Perfect systems are identical but I spose that's kinda obvious...What is common is that the voltmeter reads low.

The voltmeters read low with stock alternators, when a conversion is fitted they read were they should, 13.2V.

J.R.
CBX-tras LLC

My 79 reads 13.2 after about 30 seconds so maybe the stock system is set up correctly. I replaced the plates and regulator on the 80 and now it is reading the same so I am all set for a blood sucking night ride. Sorry for my other alternator related posts and if a moderator is reading this please delete the "REGULATOR" post so I don't look like a fool.

twinegar wrote:My 79 reads 13.2 after about 30 seconds so maybe the stock system is set up correctly. I replaced the plates and regulator on the 80 and now it is reading the same so I am all set for a blood sucking night ride. Sorry for my other alternator related posts and if a moderator is reading this please delete the "REGULATOR" post so I don't look like a fool.

All set Tom .

N.

After a week the voltmeter was reading about 10 or 11 volts at start up and until I either wrapped the rpm's past 3500 or went down the road for a couple of miles so I suspected plate slipping. Today I pulled the alternator off and sure enough a lot of marking on the surface of the plates indicating high areas even though I used sand paper on a flat surface to make them flat. This time I used my horizontal bench sander with fine paper and it is flat for sure. I also stuck a 3/32" washer behind the tension spring and reassembled and upon start-up the voltmeter climbed right up to 12.3 which tells me it is fixed. Any thoughts?

Thanks for calling it a resto but actually I didn't do a restoration, I call it a frame up clean up and partial restoration. It's my impression that a restoration would bring a bike to 100% by replacing flawed and even slightly flawed parts with new old stock Honda brand parts or Suzuki or whatever brand is being done. If I am being to tough weigh in and set me straight but the word restoration implies back to new. I wouldn't be inclined to spend the amount of money it would take to restore even my CL160 but I am able to make a bike look almost new to me and most people that look at them. Look at some of the ones on Ebay that are described as restored. I almost bought a sandcast 750 in 2007 that was completely restored to the letter of the word but knew I wouldn't be able to ride it in good conscience and backed out. Speaking of the word sandcast, I see that word stuck in the title of all kinds of 750 parts and most aren't. A lot of people looking for the fast buck parting out rusting hulks that know nothing about the subject. There.................I feel better now!

Keep in mind that the meter is showing what's in the system, not what's going to the battery. Thus a partially discharged battery will take longer to top off than one that's fresh. If you just had to crank a while to start your bike, expect it to take a bit before the battery is topped off again.

Imagine that your battery is a bucket full of voltage. When you crank a bit, you're using more power, taking longer for the alternator to "refill" the bucket.

This just one reason that the stock volt meter is a poor diagnostic tool. To get a quick picture of what your system is doing, go to any parts store and buy a K-D inductive ammeter. They're cheap and will give you a decent idea of what your system is doing.

Doesn't the voltmeter show battery condition with key on - engine off and charging volts going to battery with engine running?

I don't have the schematic nearby, but it's my understanding that the meter show voltage that the battery sees. Thus the difference between indicated voltage and what the alternator is really doing. To get a true picture, we'd need both a volt meter and an ammeter.

Anyone with some actual electrical knowledge like to chime in here?

twinegar wrote:Doesn't the voltmeter show battery condition with key on - engine off and charging volts going to battery with engine running?

Yes it does . . . . . with probably a slight drop due to 30+ year old wiring !

Bob

The ammeter shows amps going to the battery and the voltmeter shows the volts. I know the ammeter splices into the positive cable forcing the juice to pass through the gauge before going into the battery and the voltmeter connects across both poles. I guess there is probably a reason why one would want to know the amperage but it seems like you can tell if the battery is receiving a charge with either gauge. I hope an electrician or two will weigh in so I can get an education. I would like to know what each gauge brings to the rider as far as necessary information goes. When I did the frame up last fall all the electrical connections were cleaned so I should be getting the charge intended unless the stators age is what you meant by old wiring. I guess I should check resistance there. Things seem to be working right now so I am satisfied. I will be adding a set of VDO gauges soon like I already put on my 79 and might just add the ammeter.
Thanks for the responses so far.

Rick Pope wrote:I don't have the schematic nearby, but it's my understanding that the meter show voltage that the battery sees. Thus the difference between indicated voltage and what the alternator is really doing. To get a true picture, we'd need both a volt meter and an ammeter.

Anyone with some actual electrical knowledge like to chime in here?

Please refer to this page. Scroll about halfway down.

http://www.motorcycleproject.com/motorc ... geFAQ.html

That was a good read and I will save that page for future reference but I still say the CBX meter shows what is coming from the alternator. If it was only showing the level of charge in the battery then you would see a gradual increase in volts on the meter like the dial of a charger indicates during an external charge. The CBX meter also indicates when the alternator starts charging when the engine reaches the proper rpm. Maybe Honda wrongly called the gauge "VOLTS" and maybe it is designed to show both to a certain degree. I'm going to look at the wiring schematic tonight and see what it really is.......volts....amps.....or something from Roswell .

Thank you Mr. Nixon. I've long held the belief that volt meters have caused a lot of grief for the average mechanic. Not that I'm any better than average, but I grew up with lots of farm equipment around, all having ammeters, not volt meters. And the information was just as misleading. Fortunately, I had some good teachers who explained why we need to know both pieces of info to make a decent diagnosis.

A few years ago, at a rally, another CBXer (a certified mechanic) and I were watching someone swapping alternators and wondering why the fresh unit didn't show any more volts than the one thought to be defective. When we suggested getting an ammeter to test charging, we were called a "couple of dumb f--ks". We just walked away, shaking our heads.

Strictly speaking, there is no such thing as a Voltmeter. They are all ampere meters. A voltmeter just takes the measured ampere and converts it over a specified resistance into Volts. There is a small flow of current through the instrument that creates the indication of "Volt".