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Daytona Sprinter 50cc DIM HEADLIGHT

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Elektroniker
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PostPosted: 07:55 - 16 Dec 2018    Post subject: Daytona Sprinter 50cc DIM HEADLIGHT Reply with quote

It may be coincidence but after having my 50cc engine replaced with 110cc the headlamp is dim. When I start the engine and flick the headlight on it is bright but dims quite quickly so after about 10 seconds it is merely glowing.

You can see the wiring diagram here:

www.duckpoo.com/temp/Daytona_Sprinter_Wiring.pdf

More info.
The bike starts and runs fine.
The battery is charging at approx. 14 volts.

As you can see from the wiring diagram, the magneto is single-phase and feeds the rectifier/regulator from one winding on a white and yellow wire.
The yellow wire continues to the headlamp switch.

Although I'm an electronics ex-spurt, I can't figure out exactly what is inside the rectifier/regulator unit so I'm stumped as to whether it is faulty - or something else.

Thanks for any suggestions.
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Tankie
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PostPosted: 09:31 - 16 Dec 2018    Post subject: Reply with quote

check the voltage as it comes out of the mag at the plug (yellow) with the engine running, then turn on the light , look for voltage drop. check the plug and sockets are in good order, also the earthing points
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Elektroniker
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PostPosted: 13:12 - 16 Dec 2018    Post subject: Reply with quote

Thanks for your reply. Measure between yellow and "chassis"?

I did measure the voltage between yellow and chassis before I realised it was AC. It went up to 7 volts on the DC range. Meaningless, I suspect.

But let's assume that I measure, say, 15v AC with the engine at 3000 rpm. And suppose that voltage drops a lot when I switch the headlight on. Does that tell me that the magneto is faulty, or the regulator or something else?

Normally I could easily fault-find a system such as this but I can't guess what's inside the regulator.

(We had a thunderstorm overnight and everything is soaking wet. As I don't have anywhere under cover to work, I won't be able to do much until Monday.)
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Tankie
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PostPosted: 15:05 - 16 Dec 2018    Post subject: Reply with quote

Check voltage at that first plug , engine running ,then turn on the light, noting the voltage, yellow to chassis on the A/C range.
All this is checking is the output of the mag
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Tankie
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PostPosted: 15:16 - 16 Dec 2018    Post subject: Reply with quote

Normally I could easily fault-find a system such as this but I can't guess what's inside the regulator.
Well seeing as you can't guess, I will , I think there is a clipping circuit across the yellow wire .
It does no matter at this time.
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Elektroniker
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PostPosted: 17:27 - 16 Dec 2018    Post subject: Reply with quote

Tankie wrote:
Check voltage at that first plug , engine running ,then turn on the light, noting the voltage, yellow to chassis on the A/C range.
All this is checking is the output of the mag

I'll do that tomorrow - weather permitting.
(I ran a hacksaw through the skirt so that I don't have to dismantle the whole thing every time I want to access the wiring!)
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Elektroniker
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PostPosted: 09:37 - 17 Dec 2018    Post subject: Reply with quote

I managed to squeeze the bike inside my tiny workshop. Too windy to work outside. You can see the results of my tests here:

https://youtu.be/GRGPSvt9ILI

Note that a voltmeter reading would have been meaningless or at least difficult to interpret. A multimeter is designed to measure either pure DC or pure sinewave AC. The headlamp feed is neither. It's like a sinewave but with 2/3 missing!

So I used an oscilloscope to view the exact waveform. I monitored the voltage from the single-phase magneto between yellow and green (chassis) at the regulator with engine speed around 3500 rpm. Oscilloscope set to 10 volts per cm (graduation). With no load the waveform is dirty AC going up to about 45v peak-to-peak. With lights on you can see a half-wave rectified sinewave at about 40v peak-to-peak. However, it's not a true sinewave as the mark/space ratio is about 1:3. With headlight on (35W) we see a cleaner half-wave rectified sinewave of about 15 volts peak and a mark/space ratio of about 1:2.

If you view the video at around 1:20 you can see how dim the "sidelight" bulb is. The headlight is equally dim, although you can't really tell in the video.

(The misfire is a separate problem - I think!)

Link to images: http://www.DuckPoo.com/daytona/


Last edited by Elektroniker on 11:05 - 17 Dec 2018; edited 1 time in total
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Tankie
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PostPosted: 10:37 - 17 Dec 2018    Post subject: Reply with quote

I recon it's the Mac lighting coil that's down
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Elektroniker
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PostPosted: 11:21 - 17 Dec 2018    Post subject: Reply with quote

Tankie wrote:
I recon it's the Mac lighting coil that's down

I've never heard of a "Mac lighting coil". Can you please explain what it is; what it does; what it looks like; where I might find it?
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Elektroniker
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PostPosted: 13:56 - 17 Dec 2018    Post subject: Reply with quote

Oh, am I being as DIM as my headlight?

Did you mean mag(neto) winding?

Is the magneto easy/cheap to replace?
Forgive my ignorance. I know car electrics but am not familiar with bikes.
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Tankie
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PostPosted: 15:50 - 17 Dec 2018    Post subject: Reply with quote

It's the same animal, vehicle electrical systems .
You have now identified that the Mag coil could be your problem, to prove it you could disconnect the reg yellow wire and see if you get a voltage rise with the light on as you start up.
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Elektroniker
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PostPosted: 16:14 - 17 Dec 2018    Post subject: Reply with quote

It's cold and windy and darkness is falling. I think my next move will be to get my mechanic to replace the magneto and regulator in the relative comfort of his garage.

Many thanks for your help.
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Tankie
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PostPosted: 16:18 - 17 Dec 2018    Post subject: Reply with quote

From what I've found this appears to be a Greek market machine not available over here , so look foe spares locally
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Tankie
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PostPosted: 16:18 - 17 Dec 2018    Post subject: Reply with quote

From what I've found this appears to be a Greek market machine not available over here , so look foe spares locally
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Elektroniker
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PostPosted: 16:24 - 17 Dec 2018    Post subject: Reply with quote

Tankie wrote:
From what I've found this appears to be a Greek market machine not available over here, so look for spares locally

Yes, you are correct. My (Greek) mechanic will know where to look. There are plenty of these bikes around so spares shouldn't be a problem, although the cost might be! Second-hand vehicles and spares are unbelievably expensive here. Thankfully, labour is cheap, which makes it not worthwhile for me to do it myself (especially at my age).
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Elektroniker
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PostPosted: 13:46 - 20 Dec 2018    Post subject: Reply with quote

December 20, 2018 update:

I measured the battery voltage with the engine idling and it was around 13 volts, rising to 14.8 volts at 3500 rpm.

With headlight switched on (still dim) the battery voltage still measured above 14 volts. Makes no sense to me but I decided that the magneto is certainly good enough to charge the battery.

I modified the wiring, disconnecting the yellow (unregulated) lighting feed from the regulator output and connecting it to the red (regulated) output from the regulator, which goes directly to battery positive.

Lights work fine but battery voltage is around 12.5 volts even with lights off. I'm confused! I'm going to leave it like this and see if the battery maintains its charge and hoping that the regulator doesn't die with the additional load of around 45 Watts (4 Amps).

Updated this page:
http://www.DuckPoo.com/daytona/
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Elektroniker
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PostPosted: 16:36 - 04 Jan 2019    Post subject: Reply with quote

January 4, 2019 update:

The weather has been bad with rain every day so I've managed to do only a few minutes of investigative work between downpours.

However, I have established that the circuit diagram is incomplete. The Rev counter is missing from it and the yellow feed to the lighting switch changes colour before reaching the switch. There is something in line, which is not on the diagram: possibly a regulator and this may be the faulty item. Whatever it is is now draining the battery with everything off. So I have reverted to the original wiring for now so at least I can use the bike during daylight.

Meanwhile, I have fitted LED front flasher "bulbs" (with 10 Ohm resistors added to fool the flasher unit, otherwise it flashes very rapidly to indicate a blown bulb). Thankfully, there are unused female "bullet" connectors on wires from each bulb holder so I was able to fit the resistors neatly and easily. I used suitably rated resistors. 2 Watt is adequate because they are fed current intermittently. I think I could have used a higher resistance value but 10R was what I had in stock. When weather permits, I'll experiment. I had to buy "amber" LEDs, since the original flasher bulbs are varnished orange. And it's worth noting that the LED "bulbs" are polarised. They work only one way round. So test before reassembling!

I've also ordered a selection of LED headlight "bulbs" with dip/main. I doubt that these will work correctly on the half-wave rectified regulator output but they'll reduce the overall load when I get the wiring sorted. Had it not rained again today I would have done that already but the ignition switch feed is difficult to access without more dismantling.

I plan to replace the "panel" indicators with bright LEDs. These are on order. At present the bulbs are too dim to see in daylight. I might knock up a circuit to dim the LEDs at night when the lights are on.

I'll keep updating this thread as I progress.
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Elektroniker
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PostPosted: 17:15 - 18 Jan 2019    Post subject: Reply with quote

I modified the wiring again, fitted a tiny digital voltmeter and an LED headlight bulb. The latter is rated at only 6 Watts so it takes around 0.5 Amps of current (compared with the original 35W filament bulb that takes about 3 Amps).

Result is a MUCH whiter, brighter headlight beam and the battery still charges nicely at cruising speed.

Updated this page:
http://www.DuckPoo.com/daytona/

I still have a new regulator on order and a selection of LED headlight bulbs but the current setup seems OK. So I'll run it for a while and decide whether it's adequate before making any more changes.

I hope that this investigation/experimentation helps others. According to the dealer, all the small "Daytona" bikes have the "dim headlight" problem.

However, I suspect that you (Tankie) are correct and there's a hidden shunt regulator on the yellow wire and it is faulty. That reminds me, I should disconnect the yellow wire altogether, since it's no longer required and that hidden shunt regulator seems to be sucking power for no reason.

Oh, one more point: after I did the last wiring modification, there was a strong smell of burning insulation for the first kilometre. I removed covers and didn't find any melted wires so it's a mystery. (Maybe the hidden shunt regulator finally fried itself?)
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Tankie
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PostPosted: 18:00 - 18 Jan 2019    Post subject: Reply with quote

Nice one,
I'm mystified as much as you over what is in that reg. unit and the yellow wire, still it's a good fix
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Elektroniker
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PostPosted: 20:12 - 18 Jan 2019    Post subject: Reply with quote

Tankie wrote:
Nice one,
I'm mystified as much as you over what is in that reg. unit and the yellow wire, still it's a good fix


Thanks for your kind assistance. It's always nice to have someone around, even if they just "pass the spanner". But you made some useful suggestions, too. Smile

I just took the bike for a night ride. Country lane; no street lights. Wonderful! First time since I bought it that I've actually been able to fully see where I'm going!
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Tankie
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PostPosted: 20:53 - 18 Jan 2019    Post subject: Reply with quote

I think the diagram of the rec/ rectifier is a bit of a flannel ,rather like the japs did back in the 70's with their electrical boxes, it's a bit over simplified, it just shows a full wave rectifier, a non descript regulator , and the lights running unregulated nothing else.
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Elektroniker
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PostPosted: 06:30 - 19 Jan 2019    Post subject: Reply with quote

When the new regulator arrives from China (different design, more efficient, not cheap), I'll connect it up and see what difference it makes. The present regulator output varies right up to 15.2 volts, which is, in my opinion, too high. On a car it would be around 13.8 volts.
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Tankie
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PostPosted: 06:51 - 19 Jan 2019    Post subject: Reply with quote

well, that's not doing it's job, your right , I would expect to see no more than 13.8v too
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Elektroniker
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PostPosted: 22:30 - 19 Jan 2019    Post subject: Reply with quote

I've solved the "burning insulation" smell that I mentioned. A fixing lug had broken off the plastic bodywork so (unbeknown to me because I always mount from the left) it was flapping loose and was intermittently touching the exhaust pipe close to the engine!

I added a couple of extra screws to secure it. Thankfully, only a tiny bit of plastic had actually melted and isn't visible from the outside.

As for the regulator, the mystery deepens. As the yellow wire from the regulator is no longer connected to the lighting switch, I disconnected it close to the regulator. The result was that the battery voltage never rose above 12.5 volts!

So I reconnected the two sections of yellow wire and now the battery voltage has gone back to varying anywhere up to 15.2 volts. I've had to leave it like that for now, otherwise the battery won't charge. But I'll definitely fit the new regulator when it arrives.

Another fault that I had was that the "TOP" gear telltale lit in 1st gear, not 4th. The mechanic had connected pink to pink from the gearbox, assuming that this was correct. I found three unused wires exiting the gearbox and measured their resistance to ground as I changed gear. I have labelled them 2, 3 and 4.

I connected "4" to the pink wire for "TOP" so now I can tell that I'm in 4th gear at a glance. (The bike is still geared for a 50cc engine so I'm continually trying to change up! I'll change the sprockets eventually.)

Also, when I get around to it, I'll extend the three numbered wires to the speedometer housing and I'll fit LEDs for all the gears, just for fun.

My bedtime now. Greece is 2 hours ahead of the UK.

Cool
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Elektroniker
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PostPosted: 11:26 - 11 Feb 2019    Post subject: Reply with quote

The new regulator finally arrived from China. I mounted it on a piece of aluminium with a bridge rectifier and two 4700uF capacitors. Everything seems to work perfectly! Even with the lights on, it provides a constant 13.8 volts, except at very low revs.

See photo at the bottom of this page:
http://www.DuckPoo.com/daytona/
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