I have tested the 33 amp alternator on my '85K and found it lacking - 10.7 volts @ idle, 11.7 @ 2.5k and 12.7 @ 4K.

Pretty much reinforces by belief that the alternator was bad when I bought the bike.

New battery, checked all wiring/earths.

I have purchased a 50 amp unit off ebay and am having a great auto electrical remanufacturing shop local to me test/rebuild (new bearings/brushes @ minimum).

My alternator light comes on when turning the key so I don't think any problem there.

Does the 50 amp alternator behave any different than the 33 amp as far as voltage @ idle, 2.5K and 4K - up?

I'm not much of an auto/motorcycle electics kinda guy, but can follow a wiring diagram, but other than that I'm not much of a diagnostician.

I know that some car alternators have to spin to ~2.5K before they start charging, and will charge below that rpm thereafter, and others charge w/o having to rev it.

What does the K Bikes alternator do?

Thanks,

Brad

K Bike needs to have the charge light on the clocks working, it trips in about 1100rpm. My red light comes on at ignition and at tick over but goes out as soon as the revs exceed that.

At 2500rpm you should get 14.2 volts for ideal but 13.9 is acceptable.

Thanks for the info guys!

I replaced my instrument lights with an led kit. Now my charge light goes out at 2500rpm not the 1100rpm you quote. I can't remember if it went out at 1100rpm pre led upgrade.

You should not change the charge light for an LED. The resistance of a normal charge light bulb is required to excite the alternator.

bikerboy wrote:You should not change the charge light for an LED. The resistance of a normal charge light bulb is required to excite the alternator.

Would I be right in thinking that if the LED goes out at 2500rpm the alternator then charges? You would be looking at the red LED until you hit 2500rpm? I could live with that. Its just I bought a full LED set [including H4 LED bulbs] for the K so that I can power 2 night driving lights without changing the alternator.

This was the note I received when I purchased my LED upgrade kit:

"CAUTIONARY NOTE regarding the charge indicator LED:  On some bikes, you'll notice that the charge indicator warning lamp is still lit once you've started the bike.  This is because the circuitry in the voltage regulator needs to be "excited" for the alternator charging circuitry to be kick in.  All you need to do, once the bike is started, is rev it up to about 2,000-2,500 RPM until the charge indicator warning lamp goes out.  Once the warning light is out, that tells you that the alternator is working to supply power to the bike and keep the battery charged.  If you just start the bike and let it idle without getting the light to go out then the bike will be running from the battery and can drain the battery. This is a non-issue.  I've been running these kits on my bikes for tens of thousands of miles and continue to do so without any problems.."


Of course YMMV

I for one don't want to be reving the bike to 2500rpm when cold every start, even warm!

Put in a globe or resistor as suggested by the forum gurus.

Not sure that I would want to change something so far from the design that the operating instructions need to change. For the sake of 20 minutes I would put the bulb back in. I also have LEDs in my instruments, but not in the charge indicator. All my flashers, rear lights and brake lights are also LED.
I am interested in the H4 LEDs that you have bought, as far as I know no one had yet made a H4 LED that would be bright enough to drive behind.
A 32 amp alternator should be plenty to power a standard bike even with heated grips on.

brad ...sounds like you had a regulator issue ...pretty common
the regulator itself is not verry hard to change ...about 30 - 40 bucks

(but beforehand change the charge indicator globe to a new one ...they do go "soft " over time ).

like all things with brushes ...they wear out .

hope the 50 amp goes well for you

good luck !

Ghost who rides wrote:I for one don't want to be reving the bike to 2500rpm when cold every start, even warm!

Put in a globe or resistor as suggested by the forum gurus.

No need to rev to 2500 rpm immediately. But when move off you hit 2500rpm at 40mph/62kph so its not really a problem. Its only an issue if you start engine and leave it on tickover for a long time and we don't do that do we?.

I believe I have LED's in the instrument cluster too - not sure about the charge bulb 'tho....

I just figured that if I was going to take the time to R&R, then put in the best available and have some spare parts if necessary...

I might wind up putting on heated grips and eventually heated gear for wife & I, so makes sense to go the 50 amp route now - alts the same price on fleabay...

This winter I'll dig into the instrument cluster and verify that a bulb is in there and not an LED for the charge light.

Thanks for all the info!.

I am interested in the H4 LEDs that you have bought, as far as I know no one had yet made a H4 LED that would be bright enough to drive behind.


I will keep updated on the LEDs. I recently bought some 4W led ES27 bulbs for outside lights at home. I put one in last year, same rating, same light fitting, but the new ones make the older same wattage look like a candle.

I did a bit of research and went for LED H4s with maximum no of LEDS and as soon as I fit them will post my thoughts.

I have LEDs fitted all over my house now, and they are great for most lights.
I have the rear lights, indicators, parking lights and instrument lights (apart from charge) fitted to the K, but the headlight is another matter. That needs to be a very directional light with a single filament just in the correct place to make a good beam. I don't believe that a H4 with 5050 LEDs all over the place can produce the light in the correct places with the standard reflector and lens.
I will continue with the 35 watt HID/xenon conversion with the projector lens for now.

You may well be right. I got the LEDs at a very right price and won't be upset if they don't work out for the H4. But a friend of mine in France has H1 and H4 LEDs in his car and swears by them so I decided to take a shot at it. The LED H4 has no hood to stop the low light reflecting upward and blinding others, instead the lower and upper LEDs ones light separately. I will have to see how that affects low beam light because you don't have full wattage on low beam. It may well be ok because we use a lot of LED GU10 fittings which are those recessed ceiling spotlights and they seem well able to maintain a focussed light pattern.

Don't forget that we bikers in France can do what we want to our bikes, including having dipped beam headlights that don't really have a dipped beam, as we have no MOT or any other annual checks on bikes here.
I believe that the latest version of the Seat Leon car has the first LED headlights on any production car (I thought that Audi would be the first) but that is a complex system using individual reflectors for each high powered LED, and those are not just 5050 SMD LEDs, but high powered items.
I wait for your results and hope that they are what you want, but I think it is going to be 2 or 3 years yet before we see after market LED kits for dip and main beam.
I seems that I lied, Audi had production cars with LED headlights in 2008!

I suspect that what will have to happen is the original headlight unit will be dip beam only and the other lights become main beam. I may be surprised though because I am quite impressed with recent mains voltage LED light bulb technology. A lot of improvement in 12 months.

$90 dollars, cleaned up like new, new bearings, brushes and voltage regulator.

Total investment $200.

I'll be putting it in tonite/tomorrow morning - my back's bothering me...

good luck brad ....fingers crossed for you

Good lluck brad, $90 sounds like money well spent.