LCGB Forums

Hi All.
I Have a problem as when I put the lights on, the engine tries to cut or cuts out, I have fitted a new light and ignition switch. Has anybody had this problem. Anybody idea what is causing this problem. Any help will be appreciated.
Cheers
Stag

Really not my strong point but the first thing that springs to mind is a short circuit to earth when you switch the lights on acting like a kill switch. A trapped lighting wire would cause this.
Paul.

If you have standard points ignition try checking if the points are set right.

I think I would suspect a poor engine to frame earth, make sure there is good metal to metal contact at both ends.

Hi thanks,
But I can see what the points would have any thing to do with my problem.
Stag

If you have standard points ignition try checking if the points are set right

The magnetism in the flywheel might also be an issue but Captain Pugwash would be the best person to answer that one if he's about

Have you got points or is it electronic ?

If electronic disconnect the green wire (to headset) off the cdi unit and try again.

If points ? the lighting and ignition coils are separate so I can't see a connection (excuse the pun).

The old trick with 6v points systems was to close up the plug gap as turning on the lights dragged the system down, usually caused by a demagnetised flywheel but seen electronic systems cut out when there is a lighting short as well.

If points, the cause will be low flywheel magnetism (as already advised) &/or poor electrical connections throughout. Poor connections make for high resistance to the intended components & bad earths mean the 'electricity' just flows to the point of least resistance.

Hi thanks for all your comments, I should have said I am using points and my lights are nice and bright. anybody point me to where I can get the flywheel remagnatized, or where I will get a new one with a new complete stator.
Cheers
Stag

Borrow a multimeter set it to ohms check the resistance with both probes touching together this is your Zero.

Connect or touch the black probe to a good clean earth at the engine case and do the same with the red probe and you should get your same Zero reading. This will check you have a good earth to check the ignitions impedance readings.

With the black probe still connected to the engine case...
Now disconnect the green from the junction box that's the green that comes from the stator and connect the red probe to that green.

Very slowly BY HAND turn the flywheel towards TDC, at about 20 degrees before TDC the points open this is when you will see the reading on the ohms scale rise, if you rotate the flywheel back anti clockwise the points close and the resistance now drops.

The lower reading should be your Zero but no more than 0.1 ohm higher than your Zero.

With the points open the reading should be approx 0.75 ohms higher depending on the lt coil fitted. But definately no higher than 1 Ohm with the points open.

Pitted or dirty points can and do cause the engine to misfire and some times cut out when the lights are turned on.

Not saying it's your problem but you can check with a multimeter before you start spending on putting it right.

Good luck.

On the last ignition fault that I had on my own scooter it was an ignition block fault, the feed from the battery was being wrongly diverted through the switch to the ignition.
Luckily it never blew the stator but the scooter had a weird rough running sound to it every now and again, after checking everything through I checked all the positions on the switch with a multimeter and found the first position had a connection between grey (12volt DC on the switch) and the green ignition feed which is only used to switch the ignition on and off through pink to earth.

Thanks for all the replies.
Captain pugwash thanks I will try as you say and let you know how it goes. But I still cannot get my head round how the points could cause my problem, as they use different coils, as my engine is running really well, unless the flywheel is over worked, needing remagnatized.
Thanks All, much appreciated
Stag

Hi All,
Update. What I have done is disconnected the wires from the junction box, leaving the green wire connected, I then connected a 100w 12 volt electric kettle, to the brown wire from the stator and earthed it to the frame, I wanted something with a good draw, then started the engine no cutting out all running fine. I then connected the kettle to the purple wire from the stator, started the engine it is now back to cutting out. So there is a problem some ware with the stator, one of the coils, a bad connection, going to earth. Any thoughts.
Cheers
Stag

Perhaps it's just me, but I always think that the stator looks a little crowded & the close proximity of all the wires is likely to be the cause of short circuits.

You have an expert already giving you advice in Captain Pugwash & if I were you, I'd ask if he would refurbish your stator in any case....

As for remagnetising, which should involve checking by the supplier first, the last time I had this done was by Phil Gooding (Grand Prix) in Leicester.

He's selling up but if you're quick....

Have you tried closing the plug gap (not points gap) up a bit yet? I've seen this advised twice but couldn't see an obvious statement that you had/had not tried it yet.

Adam

Hi Adam,
I have not tried that yet, as I think there is a problem with one of the lighting coils shorting.
Cheers
Stag

Got my flywheel remagnetised last year waddo on here sorted it

Jem Booth can do flywheel testing and re magnetising as well

The reason for me repeating the 'close the plug gap' advice is that it is a seriously old school fix for the common issue of the bike cutting out when the lights go on. The issue is linked to flywheel magnetism and whilst the lighting and ignition are separate systems, this regularly fixes the issue.

Your issue may not be so easily sorted but it is a 1 minute adjustment to cure it or to rule it out, hence so worth the effort before going to great efforts to try other things.

Adam