Headlight problem - hi beam ok but no low beam

Hi,
I seem to habe some sort of headlight problem... The tiny bulb at the bottom works fine and the bigh beam too... But I have no low beam...
The small bulb is not powerful enough for night driving so I need to be in full beam mode to see anything. Both small and big bulbs are brand new. Any idea why?

Remove the headlight from the housing, and then with a multimeter, check the three prong electrical connector that plugs into the light. You'll need to have the ignition switch on to do this, to power the headlight circuit. Change from low beam to high beam, to test the circuits.

I'd imagine your headlight wiring is like this:
HEADLIGHT
RED with BLACK stripe, High Beam.
RED with YELLOW stripe, Low Beam.
BLACK with YELLOW stripe, the ground circuit.

If you're not familiar with how to use the multimeter, watch this video:
The best multimeter tutorial


If the electrical circuit checks good, use the multimeter to ohm check the filaments of the headlight bulb. Post back your results.

Thanks will check this... Am i supposed to put the black strobe on the ground and the red one on low and high beam connectors? And check that there is any voltage?

Your meter won't care if you reverse the probes. It will just give you "negative" values. Either way will work. The lamp just needs to see a "difference in potential". Good luck!

Ok set my multimeter on 20v

Got 10 on high beam
0.07 on low beam

So I guess there is nothing much going through on low beam. Should I suspec the electrical connector or could it potentially be the red and yellow wiring feeding the low beam?

Wires don't just go bad... there is limited chance that the wire is the problem, unless it's broken in the middle. Connectors and terminations do go bad. If I was to guess... you have a faulty switch. Get into your shop manual and follow the path of the low beam circuit from source to the lamp socket. Prove or disprove the presence of voltage, and you'll find your "open".

I'd open up the right handlebar switch pod, looking for corrosion, broken wire, or failed solder joints, as these older bikes are starting to show electrical problems. If you need soldering advise, post back, as I've got a repair procedure for this.

If not already done, would also check for corrosion or other malfunction in the dimmer switch

The dimmer switch receives battery positive voltage, and delivers the voltage to the headlight plug-in socket from the switch's high beam or low beam position.

Could spray some deoxit or other electrical connection cleaner inside the switch while flipping the switch back and forth.

Good Fortune!

I'd bet on the dimmer switch. The light "on-off" switch feeds both filaments so it would knock out both hi and lo beams.