Honda Sky SGX 50 wiring an blowing headlights By scut (Read 3,119 times)

[scut]

Hi, I  have another Honda Sky SGX 50 electrical query, seems to be a popular issue looking at some of the previous posts in this forum!

Firstly, I would really love to get my hands on a wiring diagram if anybody has one available? Noticed in a previous post that there might be one available in Dutch? 

Secondly I would really appreciate some advice on a problem I have. I am having trouble with my sgx 50 blowing the headlight and taillight when the engine is revved. 

Background is that I bought the bike as a non runner a few weeks ago.  Following various investigation I replaced the crank seals and now she starts and runs great.  Whilst I had all the bodywork off I also painted the frame as it was starting to rust quite badly in places. 

Last night I put all the bodywork back on and did a quick check to make sure everything was connected back up properly and working. All OK except when I revved the engine the headlight blew, strange I thought but maybe just an old bulb.  Switched to high beam which came on fine, revved the engine and that blew as well.

 Removed the bulb & confirmed it had blown then did a quick check a multimeter  at the headlight bulb socket.  DC voltage at the bulb holder goes from approx 6V at tick over to 50V at high revs.   Was getting late so didn't have time to do any more  investigation. 

 Strongly suspect the regulator but before I purchase I want to rule out anything else as the 5 pin regulator costs over 60 pounds and it seems a strong co-incidence that was all fine before I pulled things apart to change the crank seals. 

By the way I am assuming that the lighting system is supplied from the regulator - this is where a wiring diagram would be especially useful. 

Given I had to remove the Rotor & Stator to replace the crank seals I intend to double check I haven't done anything silly when re-assembling.  Also going to check the voltage at the battery with the engine running to see what the regulator is supplying to that part of the electrics (I think that the regulator probably has two outputs - one for the battery supplied electrics and one direct for the lights). 

One thought I've had is that when I first got the bike running the tail light was not connected up - could this cause any problems, could this have damaged the regulator due to there not being the correct load from the lighting system?  Would seem a bad design if it did as bulbs can blow in normal operation and wouldn't want  a blown bulb to result in an overloaded regulator.  The headlight seemed to work fine at that stage and did not blow. Could a bad earth somewhere be causing this if I have disturbed the wiring somewhere and not realised? Could the lighting circuit resistor be involved?

 Am not great with electrics and learning as I go along therefore any advise would be much appreciated & apologies for the long post!!

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[JR]

Indeed it sounds like you have a R/R that is blown and not doing it's job. With that much voltage to the headlights they are doomed. Also I would check the tail lioghts too. The R/R on this scooter feeds the CDI also so that could be in danger as well.

Yes you are correct on this thread we learned a lot about this scooter and if you follow it you will indeed se a diagram/manual in dutch and learn what we both learned;

thescooterprofessor.proboards.com/index.cgi?board=classroomnchinese&action=display&thread=219

There is even a vendor who sells this part listed.

On this thread you learn of the resistor that is on this scooter as well a 20W/60 ohm type and again where to buy it;

thescooterprofessor.proboards.com/index.cgi?board=classroomnchinese&action=display&thread=662

If this resistor is bad the the R/R will have no load when the lights is off and will be in danger of blowing too.

If you need any help or got questions let us know, we're here to help.

JR

[scut]

Thank you for the quick reply.

This afternoon I removed the rotor and checked all the wiring but all looks fine. Ran the multimeter across all the resistors (there are 3) and all were as per the label.

Then played around checking continuity between various connectors and all appears as per the Dutch wiring diagram.

I was surprised that, with the regulator disconnected, there is continuity between the white wire which connects the stator to the regulator and the yellow wire which connects the regulator to the lighting circuit. I measured 15 ohms. Looking at the diagram I guess the two circuits can connect via earth and the resistor.

I then thought I'd experiment with the bike running. The output from the regulator to the Cdi seems to be AC and seems to match the stator feed as far as I can tell. if this is the case I do wonder why there isn't a supply straight from the stator to the cdi, maybe I'm missing something?

The regulator output to the battery seems fine, around 14 to 15 volts.

The regulator output to the light circuit was again very high. To rule out a short between the stator output and the feed to the lights I disconnected just the regulator wire which feeds the light circuit. The actual regulator output was high again, although I guess there was no load on it so that may have an affect. There was no voltage on the light circuit though.

Think I am now pretty convinced that the regulator is bad so will bite the bullet and order one.

Has been interesting playing around and I think I have learnt a few things!

[JR]

Yesireeeee! And if this checks out and she works like it should then for future reference will you post all of the voltage findings on each leg and then we can have a referense to go by in case another person has the same issues?

All part of the learning experience as you mentioned. We'll await your outcome.

JR

[scut]

I am now actually contemplating a little re-wire rather than buying a new regulator (the regulator will cost me half what the bike cost!).

Thinking that I could disconnect the yellow lighting circuit feed from the regulator and splice it in to the battery supplied circuits as that part of the regulator output seems fine. I would need to remove the lighting circuit resistor so that it doesn't drain the battery circuit (plus it wouldn't be needed for that circuit).

Do you think this might work?

[JR]

Nope. The voltage from the stator is AC and is rectified to DC through the R/R and then is regulated by the load demand of the system. Without it you'll run a full load from the stator into the bulbs, blowing them continously.

That the problem now the R/R is allowing the full stator voltage to go to the lights. Why do they cost so much? Tried Ebay?

JR

[scut]

Maybe I didn't explain very well what I was thinking of trying.

The R/R has 3 outputs.

One to the CDI which seems ok, that is engine starts and seems to run fine.

One to the battery and the electrics which run of that circuit i.e. indicators, horn etc. This output on the R/R seems fine as the voltage is approx 14 to 14.5 volts.

The third supplies the lights and the automatic choke. This one is not fine hence blowing the bulbs.

I was thinking of disconnecting the lights/choke circuit from the bad R/R and connecting it into the good output which supplies the battery.

I think it might work but maybe it would be too much load on that R/R output. Hmmmm, not sure!

[JR]

Very rare for the R/R to have just one leg bad? I haven't looked but most of the time the resistor is for a scooter that has a on/off headlight switch. Does this scooter have one? If not then does the headlight circuit feed through the resistor?

Another possibilty would be run this circuit through the resistor and see what kind of voltage it has? If it's down in the 12 volt range then that might be a possibility too.

Running the headlights and charging the battery at the same time? Doubt it.

Again see how this resistor is set up in the circuit and remember ist's 20W/60ohm if you want to test it.

JR