Help! Electrical issue - When i rev my headlight goes out!

[bristolLambretta]

Hi all please help me find this fault!

Symptoms are when i rev my S2 Li150 with (indian!) 12volt electronic kit / no battery / 12v halogen lamp scoot my headlight dims until it goes out and then sometimes stays off and sometimes comes on. As a result my lights flash and go out as i ride! Not really a safe situation as some guy is going to think im flashing him out of a junction soon, just before i go flying over his bonnet!

I have so far checked the bulb holder and juction box for a lose conection and it is fine, the switch also seem fine as i have undone it and waggled/smacked it the lights stayed on. All wiring has been checked for loose conections and none found.

It really does seem to be realted to the revs....this is a new restoration with around 150 trouble free miles! Now it seems the lights dont work reliably!!!

I have blown a headlight and a brake light bulb already is that normal?

I have multi meter in hand but no clue what to be looking for ...any pointers.

thnaks P

[RinB]

With the volt meter check what voltage is coming out of regulator at tick over ,and then when reving the engine.
then get back & report on here m8

Trouble is very hard to find intermittant faults

[sion]

Check your throttle cable isnt touching the live wires and earthing the out

[coaster]

Could be a duff regulator

[tony]

or how about play in the crank? As you rev the motor its poss the flywheel is moving over and has cut thru the feed wire off the stator? So at lo rpm its not earthing but does when you wind the motor up?

[Diablo]

Tony could be right but thats easy to check by seeing if all your lights go out ie the back light as well.
Are you earthing the headlight through the lamp adjuster? If so run a seperate earth from the bulb holder itself to the headset body. Same place as the pink wire is earthed.

[Diablo]

Sort of related to Tonys theory is to check that you haven't trapped the yellow wire between the stator and the mag flange. This is easy to do and may also cause your problem

[bristolLambretta]

In case any Americans are reading this and need 'Closure' I have now found the problem.....having spent the day out on my scoot with no front light it was the ideal time to find this intermittent fault.. The rear lights were working, the speedo light was working just the headlight was not working at all in either postion...??? hmmm either power of duff bulb me thinks. A quick test with the multi meter and sure enough the holder was getting between 9-12 volts the filliments looked fine in the bubble so a firm waggle with some gloves on (halogen) oh what a suprise ...let there be light!

The moral of this story..? Dont buy crappy indian bulb holders!!!!

the reving thing must have just been down to vibration, but if you had seen it you may have been fooled as i was. It just seem too consitent to only be a vibration thing, you could dim the headlight on demand with the throttle!

I have now 'Modified' my indian bulb holder so it now really grips the barrel of the bulb with no play...i am now saving up for a casa or NOS headlight!

right back out on my Lammy

[coaster]

Thanks for the 'closure' I'll sleep better now

[tony]

Me too. . I think....