View Full Version : RS50 to RS125 Headlight Upgrade

06-10-2013, 09:52 PM
Hello all,
I am a new member that has followed some "bread crumbs" left by Members from another forum to here.
RS50's are rather rare here in the States and getting parts and solid tech is a chore as well.
I am looking for some more knowledge from across the pond on these common bikes (as they are to you's).
I am attempting to upgrade the wimpy headlight on my 2001 RS50 with one taken from a 2003 RS125.
The Headlights are an almost direct drop kick replacement, so fit isn't an issue.
I rewired the entire lighting circuit to be "hot" with Ignition, added a switch to turn them ON/OFF, and replaced all of the remaining lighting with LED bulbs.
Factory bulb left in Tach to show difference between LED and incandescent.
LED Bulbs used in Gauge Cluster.
RS125 with LED City Light
So my major problem is this, I now have a "no charge" condition when I turn the Headlight ON.
Everything works great up until then.
Bad news, even with replacing all the OEM lighting (less headlight bulbs) with LEDs, the factory charging system will not keep up with the extra draw of the new headlight.
Battery voltage drops to 12.1 as soon as the headlights are turned ON and slowly 11.9, 11.7, 11.5 ...
Without the headlight ON the battery voltage is 13.9 - 14.2 with the engine running 6-7 grand on tach.
I checked the AC output of the generator (as per Aprilia Workshop Manual) and got 35 - 38 volts.
I do not own an AC ammeter so I could not check the AC current output as instructed in the manual, however I do have a DC ammeter for testing fuse circuit loads.
Without the headlight ON I got a 0.2 amp draw from the battery and a 5.1 amp draw with the headlight ON. These readings were taken without the engine running so I could have a baseline current draw to compare against the stated AC current output from the manual. The manual says the generator should have 5+ AC amps output.
So, I would say I'm BUSTED !!!
Does anyone have any ideas on what can be done to get more out of the Factory Stator or what will fit in it's place that has more output ???
Thanks !!!

06-11-2013, 12:08 PM
Shouldnt use LED bulbs in the first place as there not suited for these headlight units and illigal, did you even check how much Watts the LED bulbs are?
because usualy there wattage is way higher than those of the stock bulbs as there intended for motorcycles and cars, not mopeds.

06-11-2013, 01:11 PM
RS125 runs either a H1 or H3 (Hi/Lo) bulb at 55 watts.
RS50 runs goofy 35 watt bulb for both Hi and Lo beams.
LED headlight bulbs are a joke and would never use them.
LED lighting uses less power.
LED light in headlight is for the "City" light only, H1 & H3 used in actual headlights.
OEM RS50 current draw yields 56.3 watts total used for lighting (w/o brake or turn ON).
My set-up with RS125 headlight ON and all other lighting replaced with LED 61.2 watts.
1/2 amp greater draw than RS50 OEM draw with all OEM spec bulbs.
LED lighting uses less power.
My problem and perhaps the real question here is that when turning on my headlight ALL charging stops and electrical system turns into a total loss system. Not good for very long rides at night.
As soon as the headlight is turned OFF charging returns.
Has anyone had any problems with their charging system on their RS50s ???
Has anyone every wired their lighting to the Ignition instead of the Factory way (post voltage regulator, pre rectifier)?

06-11-2013, 05:32 PM
How much Watts are the LED lights mate, the Watts indicate how much power they draw, normaly LED use less power, but replacment bulbs for cars and bikes got a resistor build in wich raises there wattage, otherwise the other lights in the dash etc. would burn out.

One other thing you can check is the Regulator, are you sure the wires are connected the right way? its depiced incorect in the manual, the Regulator should be fitted with the connecters down, the order of those wires should be Blue, Green, Yellow.

06-11-2013, 07:30 PM
Right, but these LED bulbs are not the L-Crap-O "put these in to stop rapid flash cause your too lazy or stupid to change the flasher relay" ones.
Know exactly which flavor you are referring to, these are not those ...

OEM Speedo 5w
LED Speedo 0.7w
OEM Tach 3.4w
LED Tach 0.7w
OEM Temp 1.2w
LED Temp 0.3w (x2 added second bulb socket to gauge to light up better, see pic)
OEM Indicators 1.7w (each)
LED Indicators 0.3w (each)
OEM City Light 5w
LED City Light 1w

OEM Bulb left in Tach to show diff
Second bulb socket added to Temp gauge

P.S. these are also not crap from ebay china

Anyways, I think you are on to something as well as I am ...
I did not know the wiring was illustrated wrong in the manual !!! SOLID TECH !!!
Mine is hooked up (with connectors down) Blue, Yellow, Green
I was checking into issues with the regulator but unable to find a proper test procedure in Aprilia Manual.
How to test everything else ...
I will switch them around tonight and report back, THANKS !!!

06-11-2013, 09:11 PM
xero, my bike is wired headlamps and tail lamps post voltage regulator, pre rectifier right now. the only thing going into rectified power are my brake lamp and my aim dash

i gotta go to sleep but that's how it's set up. we can talk more tomorrow.

06-11-2013, 10:09 PM
Thanks mattology !!!
Thanks RS_Patrick !!!
So I swapped around the regulator wiring as instructed by RS_Patrick ...
Good news, charging has returned !!!
I was getting some very weak / odd measurements at the regulator and was beginning to question it's state of mind (correction, my state of mind it's function).
I have however temporarily reverted JUST the headlight back to post voltage regulator, pre rectifier.
I need to get this all sorted out 100% before I switch it back to post rectifier.
I am not completely convinced that I don't have an issue with my voltage regulator.
The voltage regulator was hooked up (with connectors down) Blue, Yellow, Green from the day I bought it.
Unlike what RS_Patrick said (with connectors down) Blue, Green, Yellow.
Not sure of the potential for damage or accelerated wear but I'm gonna order a replacement just to be safe.
I am also going to order up some parts to make a trick little Battery Voltage Monitor to stuff into the dash so I can always know for sure.
Not really interested in trashing my new Shorai Lithium Iron Battery due to excessive drain or improperly regulated charging voltage.
Oh, for anyone interested, the RS125 headlight is WAY WAY WAY better than the RS50's !!!
Hey mattology, once upon a time in a far off forum you made mention of schematics for a "full wave rectifier" ...

06-12-2013, 10:16 AM
Yeah, i'm not sure if it's even necessary but I made one on an LED bike a few years ago. Not sure if it will help an RS50 or not, but if you want i can post some stuff later on today

06-12-2013, 03:35 PM
Good its sorted now.

Blue wire is ground, green is power out to bike, and the yellow is the power in from the stator, i had them reversed on mine also like yours just to test what divrence it made, i didnt see any difrence but.. i didnt check with the lights on.
For some reaon in the wiring diagram and the parts drawings the wires are shown in completly the wrong order, if there connected as in the diagram the lights dont even work :p:
Im still looking for a drawing wich shows the order correctly, but so far i have not found any.